Download Tutorial Guide AutoGrid 82 1 Advanced-Acrov5...
Advanced Tutorials AutoGrid™ v8
- October 2007 -
NUMERICAL MECHANICS APPLICATIONS
Advanced Tutorials AutoGrid™ v8.c Documentation v8.c
NUMECA International 5, Avenue Franklin Roosevelt 1050 Brussels Belgium Tel: +32 2 647.83.11 Fax: +32 2 647.93.98 Web: http://www.numeca.com
NUMERICAL MECHANICS APPLICATIONS
Contents
TABLE OF CONTENT INTRODUCTION TUTORIAL 1: Meridional Effect 1-1 INTRODUCTION 1-1.1 Introduction 1-1.2 Prerequisites 1-1.3 Problem Description 1-1.4 Preparation 1-2 MESH GENERATION 1-2.1 Create Mesh Project 1-2.2 Load Geometry & Define Main Properties 1-2.3 Set Default Topology 1-2.4 Meridional Control 1-2.5 Blade-to-Blade Control 1-2.6 Meridional Effect Generation 1-2.7 3D Mesh Generation 1-2.8 3D Mesh Visualization 1-2.9 Check Boundary Conditions & Mesh Quality 1-2.10 Save Project 1-2.11 Periodic Full Non Matching Connection 1-2.12 Full Matching Connection
1-1 1-1 1-2 1-2 1-2 1-4 1-4 1-4 1-7 1-9 1-11 1-14 1-22 1-23 1-23 1-26 1-26 1-28
TUTORIAL 2: Non-Axisymmetric Hub/Shroud 2-1 INTRODUCTION 2-1.1 Introduction 2-1.2 Prerequisites 2-1.3 Problem Description 2-1.4 Preparation 2-2 MESH GENERATION 2-2.1 Create Mesh Project 2-2.2 Load Geometry & Define Main Properties 2-2.3 Set Default Topology 2-2.4 Meridional Control 2-2.5 Blade-to-Blade Control 2-2.6 3D Mesh Generation 2-2.7 3D Mesh Visualization 2-2.8 Check Boundary Conditions & Mesh Quality 2-2.9 Save Project
Tutorials
2-1 2-1 2-2 2-2 2-2 2-4 2-4 2-4 2-11 2-13 2-14 2-17 2-18 2-19 2-21
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Contents
TUTORIAL 3: Bypass Configuration 3-1 INTRODUCTION 3-1.1 Introduction 3-1.2 Prerequisites 3-1.3 Problem Description 3-1.4 Preparation 3-2 MESH GENERATION 3-2.1 Create Mesh Project 3-2.2 Load Geometry & Define Main Properties 3-2.3 Set Default Topology 3-2.4 Meridional Control 3-2.5 Blade-to-Blade Control 3-2.6 3D Mesh Generation 3-2.7 3D Mesh Visualization 3-2.8 Check Boundary Conditions & Mesh Quality 3-2.9 Save Project
3-1 3-1 3-2 3-2 3-2 3-4 3-4 3-4 3-9 3-11 3-16 3-19 3-20 3-20 3-22
TUTORIAL 4: Tandem Row 4-1 INTRODUCTION 4-1.1 Introduction 4-1.2 Prerequisites 4-1.3 Problem Description 4-1.4 Preparation 4-2 MESH GENERATION 4-2.1 Create Mesh Project 4-2.2 Load Geometry & Define Main Properties 4-2.3 Set Default Topology 4-2.4 Meridional Control 4-2.5 Blade-to-Blade Control 4-2.6 3D Mesh Generation 4-2.7 3D Mesh Visualization 4-2.8 Check Boundary Conditions & Mesh Quality 4-2.9 Save Project
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4-1 4-1 4-2 4-2 4-2 4-4 4-4 4-4 4-7 4-8 4-9 4-12 4-13 4-14 4-16
Tutorials
Contents
TUTORIAL 5: Cascade Configuration 5-1 INTRODUCTION 5-1.1 Introduction 5-1.2 Prerequisites 5-1.3 Problem Description 5-1.4 Preparation 5-2 MESH GENERATION 5-2.1 Create Mesh Project 5-2.2 Load Geometry & Define Main Properties 5-2.3 Set Default Topology 5-2.4 Meridional Control 5-2.5 Blade-to-Blade Control 5-2.6 3D Mesh Generation 5-2.7 3D Mesh Visualization 5-2.8 Check Boundary Conditions & Mesh Quality 5-2.9 Save Project
5-1 5-1 5-2 5-2 5-2 5-4 5-4 5-4 5-9 5-10 5-11 5-15 5-15 5-16 5-18
TUTORIAL 6: Fin on Fan 6-1 INTRODUCTION 6-1.1 Introduction 6-1.2 Prerequisites 6-1.3 Problem Description 6-1.4 Preparation 6-2 MESH GENERATION 6-2.1 Create Mesh Project 6-2.2 Load Geometry & Define Main Properties 6-2.3 Set Default Topology 6-2.4 Meridional Control 6-2.5 Blade-to-Blade Control 6-2.6 3D Mesh Generation 6-2.7 3D Mesh Visualization 6-2.8 Check Boundary Conditions & Mesh Quality 6-2.9 Save Project
Tutorials
6-1 6-1 6-2 6-2 6-2 6-4 6-4 6-4 6-11 6-12 6-14 6-17 6-18 6-19 6-21
iii
Contents
TUTORIAL 7: 3D Technological Effect - Casing Treatment 7-1 INTRODUCTION 7-1.1 Introduction 7-1.2 Prerequisites 7-1.3 Problem Description 7-1.4 Preparation 7-2 MESH GENERATION 7-2.1 Open Existing Mesh Project 7-2.2 Adapt Mesh Project 7-2.3 3D Technological Effect Generation 7-2.4 Save Project
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7-1 7-1 7-2 7-2 7-2 7-4 7-4 7-4 7-7 7-17
Tutorials
What’s in This Guide ? This Tutorial Guide contains a number of advanced tutorials driving the user in AutoGrid™ v8 to mesh different internal turbomachinery configurations. In each tutorial, specific features related to mesh generation are demonstrated. Advanced Tutorials are detailed tutorials designed to introduce specific features available within AutoGrid™ v8. These tutorials provide explicit instructions for all steps of the mesh generation process. Advanced Tutorials do require as pre-requisite the knowledge of the mesh generation process presented in basic tutorials 1 to 7, and can be treated separately, in any order. They address different types of features available on both axial and centrifugal compressors, pumps and turbines.
Where to Find the Files Used in the Tutorials ? Each of the mesh generation starts from an existing geometry. The appropriate files (and any other relevant files used in the tutorial) are stored on AutoGrid™ v8 DVD-ROM, more precisely in the / DOC/_Tutorials/AutoGrid/_advanced directory.
How to Use this Guide ? Depending upon your familiarity with computational fluid dynamics and your interest in some particular configuration, you can use this tutorial guide in a variety of ways.
For the Beginner If you are beginning user of AutoGrid™, you should first read and solve basic tutorials 1 to 7, in order to familiarize yourself with the interface and basis of the mesh generation technique. You may then want to concentrate on a advanced tutorial that demonstrates features that you are going to resolve. For example, if you are planning to mesh a seal leakage, you should look at Advanced Tutorial 1.
For the Experienced User If you are an experienced user of AutoGrid™, you can read and/or solve the advanced tutorial(s) that demonstrate features that you are going to resolve. For example, if you plan to mesh a turbomachine presenting a non-axisymmetric hub, you should look at Advanced Tutorial 2.
Tutorials
1
Conventions Used in this Guide Several conventions are used in the tutorials to facilitate your learning process. Following a short introduction, each tutorial is divided into sections respectively related to the mesh generation steps from the geometry definition to the 3D mesh generation. Inputs required to execute the tutorials are restricted to the geometry, either in a ".geomTurbo" or CAD related format. The sequence of actions to be executed are described through a step-by-step approach, in the form of arabic numbers. Additional insight about some specific actions and/or features is frequently added to illustrate the tutorial further. This information is proposed for the purpose of clarity and completeness, and should not be executed. It appears in italicized type.
Contact NUMECA support team at +32-2-647.83.11 or send an e-mail to
[email protected] for any question or information you may require. To allow NUMECA support to help you out within the shortest delays, please provide a detailed description of the observed behaviour and performed analysis.
2
Tutorials
TUTORIAL 1:
Meridional Effect
1-1
Introduction
1-1.1
Introduction
The resolution of computational fluid dynamics (CFD) problems involves three main steps:
• spatial discretization of the flow equations • flow computation • visualization of the results To answer these questions, NUMECA has developed a Flow INtegrated Environment for internal and Turbomachinery assimilations. Called FINE™/Turbo, the environment integrates the following tools:
• IGG™ is an Interactive Geometry modeler and Grid generator software, based on structured multi-block techniques
• AutoGrid™ is a three-dimensional Automated Grid generation software, dedicated to turbomachinery applications. Similarly to IGG™, it is based on structured multi-block techniques
• Euranus is a state-of-the-art multi-block flow solver, able to simulate Euler and Navier-Stokes equations in the laminar, transitional and turbulent regimes
• CFView™ is a highly interactive flow visualization and post-treatment software • FINE™ Graphical User Interface is a user-friendly environment that includes the different softwares. It integrates the concept of projects and allows the user to achieve complete simulations, going from the grid generation to the flow visualization, without the need of file manipulation A turbomachine is a device in which the energy is transferred either to or from a continuously flowing fluid by the dynamic action of one or more moving blade rows. It plays a major role in particular in aircraft, marine space (liquid rockets), land propulsion system but also in hydraulic, gas and steam turbines applications. It is also involved in industrial pipeline and processing equipment such as gas, petroleum and water pumping plants. Other applications can be related to heart-assist pumps, industrial compressors and refrigeration plants, among others. The turbomachinery field includes turbines, pumps, fans, compressors. A turbomachine is composed of several basic elements including the blade (also called vane if it is non-rotating), hub, and shroud. Several technological effects involving clearances, seal leakages and cooling holes among
Tutorials
1-1
Meridional Effect
Introduction
others can complete the machine. Due to the complexity of the blade shapes, the presence of technological elements and the rotation of machine, the nature of the flow is strongly three-dimensional, often depicting complex flow paths. This tutorial is particularly adapted to the mesh generation of seal leakages in turbomachinery applications. It makes exclusive use of AutoGrid™ v8 and describes the main actions required to mesh the configuration of interest. In this tutorial you will learn how to:
• • • •
Read an existing geometrical file into AutoGrid™ v8; Control meridional flow paths and blade-to-blade mesh; Generate and control the mesh in the seal leakage; Control the quality of the mesh in the blade-to-blade and 3D mesh.
1-1.2
Prerequisites
This tutorial does not require any particular prerequisite but it is strongly recommended for beginners to perform the basic tutorials 1 to 7.
1-1.3
Problem Description
The problem to be considered is shown schematically here below (meridional view). The project consists in the mesh generation of a seal leakage on the top of the Aachen turbine rotor treated as an isolated axial-flow wheel.
1-1.4
Preparation
• Copy the files located in cdrom:\DOC\_Tutorials\AutoGrid\_advanced\Tutorial_1 to your working directory, where cdrom must be replaced by the name of your DVD-ROM.
• Start AutoGrid™ v8.x For LINUX and UNIX systems, you can access AutoGrid™ v8.x graphical user interface with the following command line igg -niversion 8x -print or igg -niversion autogrid8x -print
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Introduction
Meridional Effect
For WINDOWS systems, you can access AutoGrid™ v8.x graphical user interface from the start menu going to /Programs/NUMECA software/fine8x/IGG or /Programs/NUMECA software/autogrid8x/IGG 4
• Access the menu Modules, select AutoGrid and confirm "yes" to enter AutoGrid™ v8. You’re now ready to start the grid generation process and mesh the configuration presenting a seal leakage! AutoGrid™ v8 graphical user interface includes several windows that allow to visualize the geometry and mesh of the turbomachine simultaneously in the meridional, blade-to-blade and 3D view. The access to main menu and controls is proposed through a menu bar and a quick access pad, and is completed with a tool/icon bar. The execution of the different actions undertaken is summarized in the message box at the bottom of the interface.
Tutorials
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Meridional Effect
1-2
Mesh Generation
Mesh Generation
A step by step approach is proposed in the following lines. It aims at driving you through the various steps that need to be executed from the creation of the mesh project to the validation of the final mesh quality.
1-2.1
Create Mesh Project
1.
Close the Open Turbo Project Wizard dialog box
2.
Go to menu File -> New Project
3.
Click yes to close the active project
4.
Choose the icon Start a New Project From Scratch The Open Turbo Project Wizard dialog box enables the user to retrieve a ".trb" file (with associated grid) including the data required to regenerate a mesh on an identical or similar geometry. In this tutorial, these data will be progressively introduced based on the geometry of the project case.
1-2.2
Load Geometry & Define Main Properties
5.
Click-left row1 in Rows Definition the current row
6.
Click-left in the meridional view
7.
Go to Geometry Definition
row 1 in the Quick Access Pad (QAP) to activate
Import and Link CAD
Graphic window opens, allowing geometry import. 8.
Click-left on File
9.
Select geometry.dat file from the file chooser
10. Define
Open...
the hub curve
• Click-left on the hub as it turns to yellow • Click-right and select Link to Hub Hub curve is displayed in the meridional view.
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Tutorials
Mesh Generation
11.
Meridional Effect
Define the shroud curve
• Click-left on the shroud as it turns to yellow • Click-right and select Link to Shroud Shroud curve is displayed in the meridional view.
12. Define
the blade
• Click-left row1 in Rows Definition
row 1 in the Quick Access Pad (QAP) to activate
the current row, if not done already
• Go to Geometry
Select
Surfaces
A message will prompt to select surfaces.
• Type key binding twice to select all surfaces (they turn to red or yellow) The binding key acts as a toggle, activating or de-activating all surfaces. The View/View Solid menu acts as a toggle and allows to visualize the surfaces that are active.
• Click-right twice to quit surfaces selection and select Link to Blade Blade is displayed in the meridional view.
Tutorials
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Meridional Effect
Mesh Generation
13. Define
leading edge and trailing edge
• Click-left row1 in Rows Definition
row 1 in the Quick Access Pad (QAP) to activate
the current row, if not done already
• • • •
Click-left at blade leading edge line definition, inside the Import CAD window As it turns yellow, click-right and select Link to Leading Edge Click-left at blade trailing edge line definition, inside the Import CAD window As it turns yellow, click-right and select Link to Trailing Edge
Leading and trailing edges are displayed in the meridional view. When blade intersects hub and shroud, inlet and outlet are displayed in the meridional view.
1-6
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Mesh Generation
Meridional Effect
14. Go
to File -> Exit
15. Click-left
on Rows Definition
16. Click-right
row 1 to activate row1
on row 1 to get the contextual menu and select Properties
17. Enter
the Periodicity (number of blades). Left-click inside the string input area and type , press to confirm
18. Enter
in Rotation Speed (rpm) This speed will be transferred to FINE™ graphical user interface and ease the input of boundary conditions later on. The sign of the rotational speed is positive (+) when the blade row is rotating in the positive θ direction, and negative otherwise.
19. Select
Rotor as a row type and Axial as a row orientation
The row type and row orientation settings are only information that will not impact or control the mesh generation process. 20. Close
1-2.3
the dialog box
Set Default Topology
21. Click-left 22. Select
on Rows Definition -> row 1 to activate the row, if not done already
Grid Level/Medium through Mesh Control in Quick Access Pad
23. Estimate
the width of the first cell at the wall:
The width of the first cell close to the wall must be selected with care since the quality of the flow solution will often depend upon the capture of the flow phenomena inside the boundary layers which develop along the solid walls. Depending upon the turbulence model selected, NUMECA recommends to locate the nearest grid point along the wall, at a distance that corresponds to
Tutorials
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Meridional Effect
Mesh Generation
parietal coordinate y+ ranging from 1-5 (low Reynolds number models) or 3050 (high Reynolds number models). Assuming thermal effects must be modelled accurately, y+ can reach values as low as 0.1. The relation between the parietal coordinate y+ and width of the first cell close to the wall y is driven by the Blasius equation, expressed as follows for turbulent flows:
where: - ywall is the distance of the nearest grid point to the wall (in meter); - Vref is a reference velocity of the flow, for instance the inlet velocity (in m/s); - υ is the kinematic viscosity of the fluid (in m2/s), i.e. the dynamic viscosity divided by the density; - Lref is a reference length of the test case (in meter); - y+ is a non-dimensional value. In the present case, one can estimate that Vref=30 m/s; Lref=0.3m; υ=1.038e-5 m2/s Assuming one wishes to get y+ =1 at the wall, it comes that y = 1 x 10-5 m. Input the value of the Cell Width = in Row Mesh Control.
24. Select
(Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology
1-8
Tutorials
Mesh Generation
Meridional Effect
The default skin-topology includes 5 blocks as follows: - the skin block is a O-mesh surrounding the blade - the inlet block is a H-mesh located upstream the leading edge - the outlet block is a H-mesh located downstream the trailing edge - the up block is a H-mesh located above the blade section - the down block is a H-mesh located under the blade section outlet block
up block
inlet block
1-2.4
Tutorials
skin block
Meridional Control
25. Move
• • • • • •
down block
inlet and outlet locations
Click-right on inlet curve when highlighted in yellow in the meridional view Select Properties Select Linear - Z constant, type , press to confirm Click-right on outlet curve when highlighted in yellow in meridional view Select Properties Select Linear - Z constant, type , press to confirm
1-9
Meridional Effect
Mesh Generation
The new inlet and outlet locations are displayed in the meridional view.
You can access the control points of the inlet/outlet line and modify their location by dragging the points. The exact coordinates of the control points can also be introduced with click-right on the control point; a dialog box appears, enabling the user to enter the point coordinates in (rz) mode. You can access the properties of the inlet/outlet line by click-right on control line when highlighted and selecting "Properties". The dialog box is divided in two main parts. The first part allows to specify the reference frame. When it is set to "Relative", the control points are relative to a row and their reference depends on the position of the control line. Either the control points are relative to the row inlet and its blade leading edge, either to the leading and trailing edge, or to the blade trailing edge and the row outlet. The second part of the dialog box allows to control the properties of the meridional control line namely the shape, the cell width, the streamwise index and the number of points in streamwise direction. 26. Select
(Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology based on the new inlet/outlet locations
1-10
Tutorials
Mesh Generation
Meridional Effect
27. Go
to QAP Mesh Control
28. Modify
the number of flow path as
flow paths if necessary through Mesh Control -> Row Mesh Control -> Flow Paths Control
29. Control
The Expert section allows the user to control the visualization, the shape and the parameters related to flow path smoothing. The meaning of these parameters is detailed in the user manual. The Manual Edition mode allows the user to control directly the block faces which are used to construct flow paths. Edges can be moved, segments can be created or modified and grid points distribution on segments can be controlled. More details can be found in the user manual. 30. Keep
data identical
31. Click
on Generate
32. Close
the dialog box
1-2.5
Blade-to-Blade Control
33. Click 34. Go
on Generate B2B
to Mesh Control
Tutorials
Row Mesh Control
B2B Mesh Topology Control
Topology
1-11
Meridional Effect
Mesh Generation
By default, non-matching connections are applied at periodic boundaries. Matching connections at periodic boundaries can be obtained by activating the Matching Periodicity check button. Press Re(set) Default Topology to regenerate the mesh in the blade-to-blade plane. In most cases, the presence of non-matching connections somehow improves the orthogonality in the overall mesh. This is especially true in highly staggered configurations. 35. Keep
Matching Periodicity deactivated and all other data identical In several turbomachinery types, the blades are highly staggered (Automatic High Staggered Blade Detection within AutoGrid™). If the solid angle at the inlet (outlet) of the machine becomes greater than 450 and if the location of the inlet (outlet) limits of the domain is close to the leading edge (trailing edge) of the blades, then the default topology is not suitable anymore since the cells located near the inlet (outlet) boundary become very skewed. To improve this unexpected behaviour, AutoGrid™ uses the High Staggered Blade Optimization.
36. Deactivate
Topology option
37. Go
to Mesh Control Row Mesh Control B2B Mesh Topology Control -> Grid Points to control the number of grid points in the blade-to-blade view
38. Click-left
on the number of nodes, make the proper modification in the entry box and press to confirm the modification
The number of points specified is recommended to be 4xn + 1 (where n is an integer) to allow multigrid process on minimum 3 grid levels within FINE™. 39. Visualize
the result in blade-to-blade view after selecting Generate B2B to regenerate the flow paths and the mesh in blade-to-blade plane.
40. Deactivate 41. Close
Grid Points option
the dialog box.
to Mesh Control -> Active B2B Layer to specify the flow path (layer) on which the blade-to-blade mesh will be plotted in the blade-to-blade view
42. Go
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Mesh Generation
Meridional Effect
By default, the active layer is the hub of the machine (Active Layer (%span) set to 0). The layer selected for visualization is defined in percentage of span, going from hub (0%) to shroud (100%). 43. Enter
for example in order to visualize the mesh at 50% span
44. Select
Generate B2B to regenerate the blade-to-blade mesh on new specified layer in the blade-to-blade view Detailed analysis of mesh quality can be performed on Blade-to-Blade mesh after generation. Information on orthogonality, aspect ratio and expansion ratio can be outlined in this window using the Type pull-down menu and plotted in the blade-to-blade view on active layer selected in Mesh Control/ Active B2B Layer.
45. Check
for grid quality by clicking on
46. Select
quality criteria using the Type pull-down menu
47. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn for each row
48. Click-left
on part of the histogram to plot the concerned cells in blade-to-blade view
49. Click-left
on More info button to obtain information about minimum and maximum values of the selected criteria
Click Left
50. Close
Tutorials
the dialog box
1-13
Meridional Effect
Mesh Generation
Control -> Row Mesh Control -> Optimization Control to adapt the mesh optimization parameters if necessary to enhance the quality of the mesh
51. Go to Mesh
Optimization is performed in the form of smoothing and is executed on each layer using multi-block elliptic techniques. The number of Optimization Steps represents the number of iterations performed with the elliptic smoother. By default, 100 iterations are applied. 52. Keep
default Optimization Steps and all other data identical
53. Close
the dialog box
1-2.6
Meridional Effect Generation
1-2.6.1 Configuration Control on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active the current row, if not done already
54. Click-left 55. Click
on the button Add ZR Effect to add a meridional effect in the configuration
1-2.6.2 Geometry Definition 56. Click-left on Rows Definition
-> zr techno effect 1 in the Quick Access Pad (QAP) if not
active already 57. Go
to Geometry Definition
Import and Link CAD
Graphic window opens, allowing geometry import. 58. Select
the curves defining the active meridional effect
• Click-left and -click-left on all the curve(s) as they turn to yellow
1-14
Tutorials
Mesh Generation
Meridional Effect
• Click-right and select Import Meridional
Curves defining the meridional effect are displayed in the meridional view.
Curves defining the meridional effects are specified in the ".geomTurbo" file using the basic curve format (see User Manual for more details). AutoGrid™ provides also geometrical features used to create the solid body of meridional effects interactively. New polylines and C-splines can be created using respectively the Geometry Control subpad and the Geometry menu in the meridional effect edition mode and the steps needed to create these polylines are stored in the ".trb" template file. 59. Click-left on Rows Definition
-> zr techno effect 1 in the Quick Access Pad (QAP) if not
active already
Tutorials
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Meridional Effect
Mesh Generation
60. Click-right
on zr techno effect 1 to get the contextual menu and select Edit to access the meridional effect edition mode
When the meridional effect has several connections with the main blade channel, i.e. a seal leakage have a connection upstream the blade and a connection downstream the blade. In this case the mesh created inside the domain of the effect is divided into two part: one starting from the inlet and one starting from the outlet. At the middle part of the seal leakage, a separation line "rotor-stator" must be defined indicating the location of the division. At this line, defined in the edition mode, the two part of the mesh will be connected by a periodic connection if the connections with the main blade channel are related to the same row or a rotor/stator interface if the connections with the main blade channel are related to different rows. 61. Click
on Rotor-Stator Polyline in Geometry Control subpad to create a separation line
62. Click-left
on location (yellow spot on existing curve) where the "rotor-stator" polyline will
start 63. Click-left
on location (yellow spot on existing curve) where the "rotor-stator" polyline will
end 64. Click-right
1-16
to quit
Tutorials
Mesh Generation
Meridional Effect
No curves have to be added at the connection between the blade channel (hub or shroud) and the meridional effect. Automatically the hub and shroud curves will be used as limit of the meridional effect.
1-2.6.3 Topology Control The domain defining a technological effect must be filled by several structured 2D blocks. The block edges are mapped on the geometry. The Topology Control subpad provides the tools to create and control the blocks 65. Click-left
on Insert New Block icon in the Topology Control subpad to start to fill the
geometry 66. Click-left
to locate the first corner of the 2D block (yellow spot when attracted on existing
curve) 67. Click-left
to locate the opposite corner of the 2D block
68. Click-left
to create the 2D block
69. Click-left
on vertex (when highlighted in yellow) of the 2D block to move it when neces-
sary 70. Click-left 71. Repeat
to fix the new position of the vertex on the geometry
steps 69 and 70 for all vertices defining the 2D block
Click Left
The tool Detect Unmapped Edges in the Topology Default subpad allows to detect if the 2D blocks are well mapping the geometry. In addition, when the
Tutorials
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Meridional Effect
Mesh Generation
vertex is highlighted, the curve on which it is mapped is mentioned in the info area at the bottom of the GUI.
72. Repeat
steps 65 to 71 in order to fill the geometry defining the meridional effect while respecting the following rules:
• the 2D blocks inserted in the meridional effect have to present edges fully and not partly connected to another block edge when connected
WRONG
CORRECT
• when the edge mapping is not performed as required, a vertex needs to be inserted
Undesired M apping
CORRECT
• a block connection must be established on the separation lines and the mapping of vertices respected (no orphan vertices)
separation line
WRONG
CORRECT separation line
1-18
Tutorials
Mesh Generation
Meridional Effect
• the 2D blocks should be connected to the rotor/stator polyline with a complete face
WRONG separation line
CORRECT separation line
• the 2D blocks should be connected to the shroud or hub with only one face
WRONG
CORRECT
SHROUD
SHROUD
The blocks can be deleted by click-left on the icon
.
73. Click
on Detect Unmapped Edges in the Topology Default subpad to control that all the blocks are well mapped
Tutorials
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Meridional Effect
Mesh Generation
The tool Detect Unmapped Edges in the Topology Default subpad allows to highlight in green the edges that are not well mapped.
74. Click-right
to quit the Detect Unmapped Edges tool
1-2.6.4 Mesh Control The Topology Default subpad provides the tools to control the mesh of all the blocks filling the technological effect. 75. Keep
the Cell Width = (as the cell width imposed at step 23) and all other data identical
76. Deactivate
Periodic Full Non Matching
The Optimization Steps represents the number of iterations performed with the elliptic smoother. The Radial Expansion and Far Field Smoothing Steps are used for external cases as propeller or wind turbine applications. The Maximum Expansion Ratio and Cst Cells Percentage control the mesh that will be generated when using Default Topology. The Coarse Grid Level control the number of grid levels that will be available within FINE™. A minimum of 3 is recommended.
1-20
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Mesh Generation
Meridional Effect
77. Click
on Default Topology in the Topology Default subpad to generate the mesh into the meridional effect (seal leakage)
separation line
If desired, the default topology can be modified by the user. When click-right on any edge, a popup menu allows to impose the number of points and the point distribution.
78. Click
on Detect Channel FNMB Connection in the Topology Default subpad to visualize the connections between the meridional effect and the channel
separation line
79. Click-right 80. Click
Tutorials
to quit the Detect Channel FNMB Connection tool
on Close Edition Mode
1-21
Meridional Effect
Mesh Generation
All the actions performed during an editing session are stored in the template file (".trb") and can be replayed on similar geometries.
1-2.7
3D Mesh Generation on Rows Definition -> row 1 and zr techno effect 1 in the Quick Access Pad (QAP) to active the current row, if not done already
81. Click-left 82. Click
on the icon Generate 3D and confirm the generation
Once 3D grid generation is completed, grid quality is performed and displayed. Minimum cells skewness, the maximum expansion ratio and aspect ratio are reported, among others. Data are available for the entire mesh separately for every entity (row, technological effect, bulb). Data related to grid quality report are automatically stored in a report file, once the project file is saved. 83. Close
1-22
the dialog box. This page can also be reopened by clicking on
Tutorials
Mesh Generation
1-2.8
Meridional Effect
3D Mesh Visualization on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active the current row, if not done already
84. Click-left
85. Click-right
on row 1 and select Properties to activate Default in order to plot the full tur-
bomachine
86. Click-right 87. Click-left
in 3D view; the Quick Access Pad (QAP) is modified
88. Click-right 89.
on row 1 and select Toggle 3D View to access the shaded blades in 3D view to get the contextual menu and activate Full View
Use View menu in QAP or View/Patch Viewer... menu to toggle edge or mesh
separation line
1-2.9
Tutorials
Check Boundary Conditions & Mesh Quality
1-23
Meridional Effect
Mesh Generation
90. Check
for boundary conditions by clicking on
91. Select
UND under Type pull-down menu and check that no patches are in the patch list still set with an undefined type
It is important to make sure that no undefined patches (UND) are present in the mesh. In that case, these can usually be removed by increasing the tolerance and launching the Search procedure. 92. Select
Full Non Matching/Define... to visualize the FNMB that are automatically created between the seal leakage (meridional effect) and the shroud of the channel
93. Close
1-24
both dialog boxes
Tutorials
Mesh Generation
Meridional Effect
94. Check
95. Click
for negative cells by clicking on
on Apply The computation of the negative volumes is performed first. Negative cells can be outlined in the mesh pushing View neg cells button. Beware that the visualization of negative cells can be memory consuming when a large number of cells must be displayed. It is then advised to first check the number of negative cells by pressing the Apply button. It is mandatory to remove all negative cells before the calculation can be started.
96. Check
for grid quality by clicking on
Detailed analysis of mesh quality on 3D mesh (in blocks, at boundaries and at FNMB) can be performed only once the 3D mesh has been generated. Information on orthogonality, angular deviation, aspect ratio, expansion ratio and cell width can be outlined in this window using the Type pull-down menu. 97. Select
quality criteria using the Type pull-down menu
98. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn per block (0 = all blocks)
99. Click-left
on part of the histogram to plot the concerned cells in the 3D view
Click Left
Tutorials
1-25
Meridional Effect
Mesh Generation
100.Click-left
on More info button to obtain information about minimum and maximum values of the selected criteria
101.Close
the dialog box
1-2.10 Save Project 102.
Go to File -> Save Project As to save mesh and template files The mesh files (7 files) contain the multiblock mesh topology, geometry and grid points and the boundary condition types: ".bcs", ".cgns", ".geom" (".xmt_txt"), ".igg", ".config" and ".qualityReport".The meaning of these files is detailed in the user manual. The template files (4 files) contain the parameters and the geometry needed to reproduced the mesh with AutoGrid™: ".geomTurbo" (".geomTurbo.xmt_txt"), ".trb" and ".info". The meaning of these files is detailed in the user manual.
1-2.11 Periodic Full Non Matching Connection AutoGrid™ allows to define a straight meridional effect (periodic boundaries of meridional effect at constant θ) by introducing periodic full non matching connection with repetition between the meridional effect and the channel. In most cases, this capability improves the orthogonality in the overall mesh. This is especially true in highly staggered configurations. on Rows Definition -> zr techno effect 1 in the Quick Access Pad (QAP) if not active already
103.Click-left
104.Click-right
on zr techno effect 1 to get the contextual menu and select Edit to access the meridional effect edition mode
1-26
Tutorials
Mesh Generation
Meridional Effect
105.Activate 106.Click
Periodic Full Non Matching
on Close Edition Mode
on Rows Definition -> row 1 and zr techno effect 1 in the Quick Access Pad (QAP) to active the current row, if not done already
107.Click-left 108.Click
on the icon Generate 3D and confirm the generation
Go to File -> Save Project As to save mesh and template files
109.
Tutorials
1-27
Meridional Effect
Mesh Generation
1-2.12 Full Matching Connection AutoGrid™ allows to define a full matching connection between the meridional effect and the channel by adding fixed control lines into the channel. This capability required in most cases more points in the mesh and an orthogonality that will not be improved in the overall mesh. This is especially true in highly staggered configurations. 110.Select
meridional view by click-left on it to active the view, if not done already
Mesh Control -> Row Mesh Control -> Add Z Constant Line to add z-constant lines to map the meridional effect
111.Select
112.Click-left
on shroud in the meridional view to add a z-constant line
113.Repeat step 112 three
times to map all the limits of the connections of the meridional effect
with the channel 114.Click-right
to quit the menu related to the creation of z-constant line
Ctrl Line 1 Ctrl Line 2
Ctrl Line 3 Ctrl Line 4
Click Left
Ctrl Line 1
You can access the control points of the z-constant line and modify their location by click-left and dragging the points. The exact coordinates of the control points can also be introduced with click-right on the control point; a dialog box appears, enabling the user to enter the point coordinates in (rz) mode. You can access the properties of the z-constant line by click-right on control line when highlighted and selecting "Properties". The dialog box is divided in two main parts. The first part allows to specify the reference frame. When it is set to "Relative", the control points are relative to a row and their reference depends on the position of the control line. Either the control points are relative to the row inlet and its blade leading edge, either to the leading and trailing edge, or to the blade trailing edge and the row outlet. The second part of
1-28
Tutorials
Mesh Generation
Meridional Effect
the dialog box allows to control the properties of the meridional control line namely the shape, the cell width, the streamwise index and the number of points in streamwise direction. 115.Click-right 116.
on first control line when highlighted in yellow
Select Properties
117.Activate 118.Set
Linear
the cell width to
Click Right
119.Click-left
on the three control lines and apply steps 117 and 118
120.Close dialog
box
on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active the current row, if not done already
121.Click-left 122.Select
(Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology considering the four new control lines
In the blade-to-blade view, additional H-blocks are appearing.Furhermore, in some cases, the default topology may change from normal to high staggered (in this case the blade is high staggered at trailing edge).
Tutorials
1-29
Meridional Effect
Mesh Generation
Ctrl Line 1
Ctrl Line 2
Ctrl Line 3 Ctrl Line 4
In the edition mode of the meridional effect, the type connection can be controlled. on Rows Definition -> zr techno effect 1 in the Quick Access Pad (QAP) if not active already
123.Click-left
124.Click-right
on zr techno effect 1 to get the contextual menu and select Edit to access the meridional effect edition mode
125.Click
on Detect Channel Matching Connection in the Topology Default subpad to visualize the connections between the meridional effect and the channel
126.Click-right
to quit the Detect Channel Matching Connection tool
An additional control line needs to be added to define both matching connections because the connection of the meridional effect with the channel close to the trailing edge is defined by two blocks. 127.Click
on Solid Polyline in Geometry Control subpad to create a separation line
128.Click-left
on location (yellow spot on existing curve) where the "solid" polyline will start (at the connection between the two blocks)
1-30
Tutorials
Mesh Generation
Meridional Effect
129.Click-left
on location (yellow spot on existing curve) where the "solid" polyline will end (anywhere in the channel)
Click Left Click Left
This new solid polyline will allow the mapping of the new control line. 130.Click-right 131.Click
to quit
on Close Edition Mode
132.Select
meridional view by click-left on it to active the view, if not done already
Mesh Control -> Row Mesh Control -> Add Z Constant Line to add z-constant lines to map the meridional effect
133.Select
134.Click-left
on shroud in the meridional view to add a z-constant line at the connection with the channel close to the trailing edge (mapping on the new solid polyline)
135.Click-right 136.Select
Properties
137.Activate 138.Set
Tutorials
on last control line when highlighted in yellow
Linear
the cell width to
1-31
Meridional Effect
Mesh Generation
139.Close dialog
box
on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active the current row, if not done already
140.Click-left 141.Select
(Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology considering the four new control lines
In the blade-to-blade view, one additional H-block is appearing between control lines 3 and 5.
Ctrl Line 1
Ctrl Line 2
Ctrl Line 5 Ctrl Line 3
Ctrl Line 4
In the edition mode of the meridional effect, the type connection can be controlled. on Rows Definition -> zr techno effect 1 in the Quick Access Pad (QAP) if not active already
142.Click-left
143.Click-right
on zr techno effect 1 to get the contextual menu and select Edit to access the meridional effect edition mode
144.Click
on Detect Channel Matching Connection in the Topology Default subpad to visualize the connections between the meridional effect and the channel
1-32
Tutorials
Mesh Generation
Meridional Effect
145.Click-right
to quit the Detect Channel Matching Connection tool
Both connections between the meridional effect and the channel are recognized as matching connections. 146.Click
on Close Edition Mode
on Rows Definition -> row 1 and zr techno effect 1 in the Quick Access Pad (QAP) to active the current row, if not done already
147.Click-left 148.Go
to QAP Mesh Control
149.Modify 150.Click
Tutorials
the number of flow path as
on the icon Generate 3D and confirm the generation
1-33
Meridional Effect
Mesh Generation
Full Non Matching
Full Matching
Go to File -> Save Project As to save mesh and template files
151.
1-34
Tutorials
TUTORIAL 2:
Non-Axisymmetric Hub/Shroud
2-1
Introduction
2-1.1
Introduction
The resolution of computational fluid dynamics (CFD) problems involves three main steps:
• spatial discretization of the flow equations • flow computation • visualization of the results To answer these questions, NUMECA has developed a Flow INtegrated Environment for internal and Turbomachinery assimilations. Called FINE™/Turbo, the environment integrates the following tools:
• IGG™ is an Interactive Geometry modeler and Grid generator software, based on structured multi-block techniques
• AutoGrid™ is a three-dimensional Automated Grid generation software, dedicated to turbomachinery applications. Similarly to IGG™, it is based on structured multi-block techniques
• Euranus is a state-of-the-art multi-block flow solver, able to simulate Euler and Navier-Stokes equations in the laminar, transitional and turbulent regimes
• CFView™ is a highly interactive flow visualization and post-treatment software • FINE™ Graphical User Interface is a user-friendly environment that includes the different softwares. It integrates the concept of projects and allows the user to achieve complete simulations, going from the grid generation to the flow visualization, without the need of file manipulation A turbomachine is a device in which the energy is transferred either to or from a continuously flowing fluid by the dynamic action of one or more moving blade rows. It plays a major role in particular in aircraft, marine space (liquid rockets), land propulsion system but also in hydraulic, gas and steam turbines applications. It is also involved in industrial pipeline and processing equipment such as gas, petroleum and water pumping plants. Other applications can be related to heart-assist pumps, industrial compressors and refrigeration plants, among others. The turbomachinery field includes turbines, pumps, fans, compressors. A turbomachine is composed of several basic elements including the blade (also called vane if it is non-rotating), hub, and shroud. Several technological effects involving clearances, seal leakages and cooling holes among
Tutorials
2-1
Non-Axisymmetric Hub/Shroud
Introduction
others can complete the machine. Due to the complexity of the blade shapes, the presence of technological elements and the rotation of machine, the nature of the flow is strongly three-dimensional, often depicting complex flow paths. This tutorial is particularly adapted to the mesh generation of a turbomachine presenting a hub and/or shroud non-axisymmetric. It makes exclusive use of AutoGrid™ v8 and describes the main actions required to mesh the configuration of interest. In this tutorial you will learn how to:
• • • • •
Read an existing geometrical file into AutoGrid™ v8; Control meridional flow paths when hub/shroud non-axisymmetric; Control blade-to-blade mesh; Control the mesh projection on the hub/shroud non-axisymmetric; Control the quality of the mesh in the blade-to-blade and 3D mesh.
2-1.2
Prerequisites
This tutorial does not require any particular prerequisite but it is strongly recommended for beginners to perform the basic tutorials 1 to 7.
2-1.3
Problem Description
The problem to be considered is shown schematically here below. The project consists in the mesh generation of a Aachen turbine stator (treated as an isolated axial-flow wheel) when presenting a non-axisymmetric hub.
2-1.4
Preparation
• Copy the files located in cdrom:\DOC\_Tutorials\AutoGrid\_advanced\Tutorial_2 to your working directory, where cdrom must be replaced by the name of your DVD-ROM.
• Start AutoGrid™ v8.x For LINUX and UNIX systems, you can access AutoGrid™ v8.x graphical user interface with the following command line igg -niversion 8x -print or igg -niversion autogrid8x -print
2-2
Tutorials
Introduction
Non-Axisymmetric Hub/Shroud
For WINDOWS systems, you can access AutoGrid™ v8.x graphical user interface from the start menu going to /Programs/NUMECA software/fine8x/IGG or /Programs/NUMECA software/autogrid8x/IGG 4
• Access the menu Modules, select AutoGrid and confirm "yes" to enter AutoGrid™ v8. You’re now ready to start the grid generation process and mesh the non-axisymmetric configuration! AutoGrid™ v8 graphical user interface includes several windows that allow to visualize the geometry and mesh of the turbomachine simultaneously in the meridional, blade-to-blade and 3D view. The access to main menu and controls is proposed through a menu bar and a quick access pad, and is completed with a tool/icon bar. The execution of the different actions undertaken is summarized in the message box at the bottom of the interface.
Tutorials
2-3
Non-Axisymmetric Hub/Shroud
2-2
Mesh Generation
Mesh Generation
A step by step approach is proposed in the following lines. It aims at driving you through the various steps that need to be executed from the creation of the mesh project to the validation of the final mesh quality.
2-2.1
Create Mesh Project
1.
Close the Open Turbo Project Wizard dialog box
2.
Go to menu File -> New Project
3.
Click yes to close the active project
4.
Choose the icon Start a New Project From Scratch The Open Turbo Project Wizard dialog box enables the user to retrieve a ".trb" file (with associated grid) including the data required to regenerate a mesh on an identical or similar geometry. In this tutorial, these data will be progressively introduced based on the geometry of the project case.
2-2.2
Load Geometry & Define Main Properties
5.
Click-left row1 in Rows Definition the current row
6.
Click-left in the meridional view
7.
Go to Geometry Definition
row 1 in the Quick Access Pad (QAP) to activate
Import and Link CAD
Graphic window opens, allowing geometry import. 8.
Click-left on File
9.
Select geometry.dat file from the file chooser
10. Define
Open...
the hub curve
• Click-left on the hub as it turns to yellow • Click-right and select Link to Hub Hub curve is displayed in the meridional view.
2-4
Tutorials
Mesh Generation
11.
Non-Axisymmetric Hub/Shroud
Define the shroud curve
• Click-left on the shroud as it turns to yellow • Click-right and select Link to Shroud Shroud curve is displayed in the meridional view.
In addition to the axisymmetric hub and shroud curves defining the meridional domain, 3D surfaces defining the non-axisymmetric end walls must be defined. These can be directly specified in the ".geomTurbo" file (more details in User Manual) or imported through the Import CAD window. 12. Define
the non-axisymmetric surface defining the hub
• Click-left on the surface defining the hub when highlighted in blue, it turns to yellow • Click-right and select Link Non Axi to Hub
Click Left
Tutorials
2-5
Non-Axisymmetric Hub/Shroud
Mesh Generation
The 3D surfaces defining the non-axisymmetric end walls must present the same peridiocity as the row. 13. Define
the blade
• Click-left row1 in Rows Definition
row 1 in the Quick Access Pad (QAP) to activate
the current row, if not done already
• Click-left on first surface defining the blade when highlighted in blue (it turns to red or yellow)
• Click-middle to select the second surface defining the blade • - click-left on second surface defining the blade when highlighted in blue (it turns to red or yellow)
Click Left
Click Middle Click Left
The View/View Solid menu acts as a toggle and allows to visualize the surfaces that are active.
• Click-right and select Link to Blade Blade is displayed in the meridional view.
2-6
Tutorials
Mesh Generation
Non-Axisymmetric Hub/Shroud
14. Define
leading edge and trailing edge
• Click-left row1 in Rows Definition
row 1 in the Quick Access Pad (QAP) to activate
the current row, if not done already
• • • •
Click-left at blade leading edge line definition, inside the Import CAD window As it turns yellow, click-right and select Link to Leading Edge Click-left at blade trailing edge line definition, inside the Import CAD window As it turns yellow, click-right and select Link to Trailing Edge Leading and trailing edges are displayed in the meridional view. When blade intersect hub and shroud, inlet and outlet are displayed in the meridional view.
15. Go
to File -> Exit
16. Click-left
on Rows Definition
17. Click-right
row 1 to activate row1
on row 1 to get the contextual menu and select Properties
18. Enter
the Periodicity (number of blades). Left-click inside the string input area and type , press to confirm
19. Enter
in Rotation Speed (rpm) This speed will be transferred to FINE™ graphical user interface and ease the input of boundary conditions later on. The sign of the rotational speed is positive (+) when the blade row is rotating in the positive θ direction, and negative otherwise.
20. Select
Stator as a row type and Axial as a row orientation
The row type and row orientation settings are only information that will not impact or control the mesh generation process.
Tutorials
2-7
Non-Axisymmetric Hub/Shroud
Mesh Generation
The non axisymmetric end walls generation is controlled into the Row Properties dialog box.
21. Keep
Non-Axisymmetric Hub active The "Non-Axisymmetric Hub & Shroud" is used to enable or disabled the mesh adaptation on the specified non axisymmetric surfaces.
22. Keep
Projection Along Face Normal active by default When the non axisymmetric surface is not intersecting the axisymmetric mesh: The "Projection Along Face Normal" is projecting the mesh on the surface using the hub or shroud normal face directions. Therefore, as on the connected face boundary the computed normal can be different for both faces, the matching connection may become non-matching. The "Projection Along Grid Line" is projecting the mesh on the surface using the spanwise grid line direction to compute the normal. This approach allows to avoid non-matching connections.
23. Keep
2-8
Repair Non-projected Points active by default
Tutorials
Mesh Generation
Non-Axisymmetric Hub/Shroud
The "Repair Non-projected Points" allows to correct non-well projected points (i.e. when the mesh points on boundaries are close to hub or shroud surface limits). 24. Set
the Geometry Repetition to The non-axisymmetric 3D surfaces must cover all the hub or shroud blade to blade domain of the axisymmetric mesh. If the specified surfaces does not cover the entire domain as shown in the next figure, the Geometry Repetition option allows the user to repeat the entered surfaces by rotation on both sides.
The "Display Non-Axisymmetric Hub & Shroud" is used to display the nonaxisymmetric surfaces in the 3D view 25. Close
the dialog box At the end of the 3D blade row generation, the mesh adaptation on the nonaxisymmetric surfaces is performed automatically. The axisymmetric mesh is adapted by hub to shroud grid points redistribution along the curve obtained by intersecting the surfaces with the hub to shroud grid lines. It is thus recommended to generate a axisymmetric mesh covering completely the nonaxisymmetric surfaces.
26. Click-left 27. Go
in the meridional view
to Geometry Definition
28. Click-left 29. Select
Import and Link CAD
on the surface defining the hub when highlighted in blue, it turns to yellow
Geometry/Modify Surface/Add uv Curves
30. Click-left
on the surface in order to define new curves plotting the non-axisymmetry appearing on the hub
31. Click-left
on the new curve until it turns yellow
32. Click-right
Click Left
Tutorials
and select Import Meridional
Click Left
2-9
Non-Axisymmetric Hub/Shroud
Mesh Generation
The limit of the non-axisymmetric hub is appearing in the meridional view.
33. Move
hub curve to create a channel including the non-axisymmetric effect
• Click-left in the meridional view • Go to Geometry Definition Edit Hub to visualize the vertices defining the hub • Click-left on vertex (at inlet) and define its new position in the keyboard input area in ZRTH coordinates where Z is the Zinlet and R is lower than the Rmin of the non-axisymmetric effect:
• Click-left on vertex (at outlet) and define its new position in the keyboard input area in ZRTH coordinates where Z is the Zoutlet and R is lower than the Rmin of the non-axisymmetric effect:
• Click-right to regenerate the channel
The hub appears as a dashed green line because it is no more mapping on a curve.
2-10
Tutorials
Mesh Generation
Non-Axisymmetric Hub/Shroud
The blade is no more intersecting the new hub. The blade needs to be extended. 34. Click-left
on Rows Definition
35. Click-right 36. Select
row 1
Blades
Main Blade
on Main Blade to get the contextual menu and select Expand Geometry
Hub treatment/expand
• Set Cut offset to • Set Extension offset to
• Apply to extend the blade MERIDIONAL
Cut Offset = 0.001 [m] ≈ 0.0003 [m]
Expand Offset = 0.001 [m]
The tool Geometry/Distance allows to measure the distance between two points in the active view.
2-2.3
Set Default Topology
37. Click-left 38. Select
Tutorials
on Rows Definition -> row 1 to activate the row, if not done already
Grid Level/Medium through Mesh Control in Quick Access Pad
2-11
Non-Axisymmetric Hub/Shroud
39. Estimate
Mesh Generation
the width of the first cell at the wall:
The width of the first cell close to the wall must be selected with care since the quality of the flow solution will often depend upon the capture of the flow phenomena inside the boundary layers which develop along the solid walls. Depending upon the turbulence model selected, NUMECA recommends to locate the nearest grid point along the wall, at a distance that corresponds to parietal coordinate y+ ranging from 1-5 (low Reynolds number models) or 3050 (high Reynolds number models). Assuming thermal effects must be modelled accurately, y+ can reach values as low as 0.1. The relation between the parietal coordinate y+ and width of the first cell close to the wall y is driven by the Blasius equation, expressed as follows for turbulent flows:
where: - ywall is the distance of the nearest grid point to the wall (in meter); - Vref is a reference velocity of the flow, for instance the inlet velocity (in m/s); - υ is the kinematic viscosity of the fluid (in m2/s), i.e. the dynamic viscosity divided by the density; - Lref is a reference length of the test case (in meter); - y+ is a non-dimensional value. In the present case, one can estimate that Vref=30 m/s, Lref=0.3m and υ=1.038e-5 m2/s Assuming one wishes to get y+ =1 at the wall, it comes that y = 1 x 10-5 m. Input the value of the Cell Width = in Row Mesh Control.
40. Select
(Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology
2-12
Tutorials
Mesh Generation
Non-Axisymmetric Hub/Shroud
The flow paths are covering the non-axisymmetric hub.
The default skin-topology includes 5 blocks as follows: - the skin block is a O-mesh surrounding the blade - the inlet block is a H-mesh located upstream the leading edge - the outlet block is a H-mesh located downstream the trailing edge - the up block is a H-mesh located above the blade section - the down block is a H-mesh located under the blade section up block
inlet block outlet block skin block down block
2-2.4 41.
Meridional Control Go to QAP Mesh Control
42. Modify
the number of flow path as
flow paths if necessary through Mesh Control -> Row Mesh Control -> Flow Paths Control
43. Control
Tutorials
2-13
Non-Axisymmetric Hub/Shroud
Mesh Generation
The Expert section allows the user to control the visualization, the shape and the parameters related to flow path smoothing. The meaning of these parameters is detailed in the user manual. The Manual Edition mode allows the user to control directly the block faces which are used to construct flow paths. Edges can be moved, segments can be created or modified and grid points distribution on segments can be controlled. More details can be found in the user manual. 44. Keep
data identical
45. Click
on Generate
46. Close
the dialog box
2-2.5
Blade-to-Blade Control
47. Click 48. Go
on Generate B2B
to Mesh Control
2-14
Row Mesh Control
B2B Mesh Topology Control
Topology
Tutorials
Mesh Generation
Non-Axisymmetric Hub/Shroud
By default, non-matching connections are applied at periodic boundaries. Matching connections at periodic boundaries can be obtained by activating the Matching Periodicity check button. Press Re(set) Default Topology to regenerate the mesh in the blade-to-blade plane. In most cases, the presence of non-matching connections somehow improves the orthogonality in the overall mesh. This is especially true in highly staggered configurations. 49. Keep
Matching Periodicity deactivated and all other data identical In several turbomachinery types, the blades are highly staggered (Automatic High Staggered Blade Detection within AutoGrid™). If the solid angle at the inlet (outlet) of the machine becomes greater than 450 and if the location of the inlet (outlet) limits of the domain is close to the leading edge (trailing edge) of the blades, then the default topology is not suitable anymore since the cells located near the inlet (outlet) boundary become very skewed. To improve this unexpected behaviour, AutoGrid™ uses the High Staggered Blade Optimization.
50. Deactivate
Topology option
51. Go
to Mesh Control Row Mesh Control B2B Mesh Topology Control -> Grid Points to control the number of grid points in the blade-to-blade view
52. Click-left
on the number of nodes, make the proper modification in the entry box and press to confirm the modification
The number of points specified is recommended to be 4xn + 1 (where n is an integer) to allow multigrid process on minimum 3 grid levels within FINE™. 53. Visualize
the result in blade-to-blade view after selecting Generate B2B to regenerate the flow paths and the mesh in blade-to-blade plane.
54. Deactivate 55. Close
Grid Points option
the dialog box.
to Mesh Control -> Active B2B Layer to specify the flow path (layer) on which the blade-to-blade mesh will be plotted in the blade-to-blade view
56. Go
Tutorials
2-15
Non-Axisymmetric Hub/Shroud
Mesh Generation
By default, the active layer is the hub of the machine (Active Layer (%span) set to 0). The layer selected for visualization is defined in percentage of span, going from hub (0%) to shroud (100%). 57. Enter
for example in order to visualize the mesh at 50% span
58. Select
Generate B2B to regenerate the blade-to-blade mesh on new specified layer in the blade-to-blade view Detailed analysis of mesh quality can be performed on Blade-to-Blade mesh after generation. Information on orthogonality, aspect ratio and expansion ratio can be outlined in this window using the Type pull-down menu and plotted in the blade-to-blade view on active layer selected in Mesh Control/ Active B2B Layer.
59. Check
for grid quality by clicking on
60. Select
quality criteria using the Type pull-down menu
61. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn for each row
62. Click-left
on part of the histogram to plot the concerned cells in blade-to-blade view
63. Click-left
on More info button to obtain information about minimum and maximum values of the selected criteria
Click Left
64. Close
the dialog box
Control -> Row Mesh Control -> Optimization Control to adapt the mesh optimization parameters if necessary to enhance the quality of the mesh
65. Go to Mesh
Optimization is performed in the form of smoothing and is executed on each layer using multi-block elliptic techniques. The number of Optimization Steps represents the number of iterations performed with the elliptic smoother. By default, 100 iterations are applied.
2-16
Tutorials
Mesh Generation
Non-Axisymmetric Hub/Shroud
66. Keep
default Optimization Steps and all other data identical
67. Close
the dialog box
2-2.6
3D Mesh Generation on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active the current row, if not done already
68. Click-left 69. Click
on the icon Generate 3D and confirm the generation
At the end of the 3D blade row generation, the mesh adaptation on the nonaxisymmetric hub is performed automatically. The axisymmetric mesh is adapted by hub to shroud grid points redistribution along the curve obtain by intersecting the surfaces with the hub to shroud grid lines.
Once 3D grid generation is completed, grid quality is performed and displayed. Minimum cells skewness, the maximum expansion ratio and aspect ratio are reported, among others. Data are available for the entire mesh separately for every entity (row, technological effect, bulb). Data related to grid quality report are automatically stored in a report file, once the project file is saved.
Tutorials
2-17
Non-Axisymmetric Hub/Shroud
70. Close
2-2.7
Mesh Generation
the dialog box. This page can also be reopened by clicking on
3D Mesh Visualization on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active the current row, if not done already
71. Click-left
72. Click-right
on row 1 and select Properties to activate Default in order to plot the full tur-
bomachine
73. Click-right 74. Click-left
in 3D view; the Quick Access Pad (QAP) is modified
75. Click-right 76.
on row 1 and select Toggle 3D View to access the shaded blades in 3D view to get the contextual menu and activate Full View
Use View menu in QAP or View/Patch Viewer... menu to toggle edge or mesh
Non-Axisymmetric Hub
Non-Axisymmetric Hub
2-18
Tutorials
Mesh Generation
2-2.8
Non-Axisymmetric Hub/Shroud
Check Boundary Conditions & Mesh Quality
77. Check
for boundary conditions by clicking on
78. Select
UND under Type pull-down menu and check that no patches are in the patch list still set with an undefined type
It is important to make sure that no undefined patches (UND) are present in the mesh. In that case, these can usually be removed by increasing the tolerance and launching the Search procedure.
Tutorials
79. Close
dialog box
80. Check
for negative cells by clicking on
2-19
Non-Axisymmetric Hub/Shroud
81. Click
Mesh Generation
on Apply The computation of the negative volumes is performed first. Negative cells can be outlined in the mesh pushing View neg cells button. Beware that the visualization of negative cells can be memory consuming when a large number of cells must be displayed. It is then advised to first check the number of negative cells by pressing the Apply button. It is mandatory to remove all negative cells before the calculation can be started.
82. Check
for grid quality by clicking on
Detailed analysis of mesh quality on 3D mesh (in blocks, at boundaries and at FNMB) can be performed only once the 3D mesh has been generated. Information on orthogonality, angular deviation, aspect ratio, expansion ratio and cell width can be outlined in this window using the Type pull-down menu. 83. Select
quality criteria using the Type pull-down menu
84. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn per block (0 = all blocks)
85. Click-left
on part of the histogram to plot the concerned cells in the 3D view
Click Left
86. Click-left
on More info button to obtain information about minimum and maximum values of the selected criteria
87. Close
2-20
the dialog box
Tutorials
Mesh Generation
2-2.9 88.
Non-Axisymmetric Hub/Shroud
Save Project Go to File -> Save Project As to save mesh and template files The mesh files (7 files) contain the multiblock mesh topology, geometry and grid points and the boundary condition types: ".bcs", ".cgns", ".geom" (".xmt_txt"), ".igg", ".config" and ".qualityReport".The meaning of these files is detailed in the user manual. The template files (4 files) contain the parameters and the geometry needed to reproduced the mesh with AutoGrid™: ".geomTurbo" (".geomTurbo.xmt_txt"), ".trb" and ".info". The meaning of these files is detailed in the user manual.
Tutorials
2-21
Non-Axisymmetric Hub/Shroud
2-22
Mesh Generation
Tutorials
TUTORIAL 3:
Bypass Configuration
3-1
Introduction
3-1.1
Introduction
The resolution of computational fluid dynamics (CFD) problems involves three main steps:
• spatial discretization of the flow equations • flow computation • visualization of the results To answer these questions, NUMECA has developed a Flow INtegrated Environment for internal and Turbomachinery assimilations. Called FINE™/Turbo, the environment integrates the following tools:
• IGG™ is an Interactive Geometry modeler and Grid generator software, based on structured multi-block techniques
• AutoGrid™ is a three-dimensional Automated Grid generation software, dedicated to turbomachinery applications. Similarly to IGG™, it is based on structured multi-block techniques
• Euranus is a state-of-the-art multi-block flow solver, able to simulate Euler and Navier-Stokes equations in the laminar, transitional and turbulent regimes
• CFView™ is a highly interactive flow visualization and post-treatment software • FINE™ Graphical User Interface is a user-friendly environment that includes the different softwares. It integrates the concept of projects and allows the user to achieve complete simulations, going from the grid generation to the flow visualization, without the need of file manipulation A turbomachine is a device in which the energy is transferred either to or from a continuously flowing fluid by the dynamic action of one or more moving blade rows. It plays a major role in particular in aircraft, marine space (liquid rockets), land propulsion system but also in hydraulic, gas and steam turbines applications. It is also involved in industrial pipeline and processing equipment such as gas, petroleum and water pumping plants. Other applications can be related to heart-assist pumps, industrial compressors and refrigeration plants, among others. The turbomachinery field includes turbines, pumps, fans, compressors. A turbomachine is composed of several basic elements including the blade (also called vane if it is non-rotating), hub, and shroud. Several technological effects involving clearances, seal leakages and cooling holes among
Tutorials
3-1
Bypass Configuration
Introduction
others can complete the machine. Due to the complexity of the blade shapes, the presence of technological elements and the rotation of machine, the nature of the flow is strongly three-dimensional, often depicting complex flow paths. This tutorial is particularly adapted to the mesh generation of bypass turbomachine applications (airplane engine). It makes exclusive use of AutoGrid™ v8 and describes the main actions required to mesh the configuration of interest. In this tutorial you will learn how to:
• • • •
3-1.2
Read an existing geometrical file into AutoGrid™ v8; Control meridional flow paths especially at the nozzle; Control the blade-to-blade mesh; Control the quality of the mesh in the blade-to-blade and 3D mesh.
Prerequisites
This tutorial does not require any particular prerequisite but it is strongly recommended for beginners to perform the basic tutorials 1 to 7.
3-1.3
Problem Description
The problem to be considered is shown schematically here below (meridional view). The project consists in the mesh generation of a bypass configuration (part of an airplane engine). The configuration is composed by a fan in front of the nozzle, three rows in the down bypass and one row in the up bypass
3-1.4
Preparation
• Copy the files located in cdrom:\DOC\_Tutorials\AutoGrid\_advanced\Tutorial_3 to your working directory, where cdrom must be replaced by the name of your DVD-ROM.
• Start AutoGrid™ v8.x
3-2
Tutorials
Introduction
Bypass Configuration
For LINUX and UNIX systems, you can access AutoGrid™ v8.x graphical user interface with the following command line igg -niversion 8x -print or igg -niversion autogrid8x -print For WINDOWS systems, you can access AutoGrid™ v8.x graphical user interface from the start menu going to /Programs/NUMECA software/fine8x/IGG or /Programs/NUMECA software/autogrid8x/IGG
4
• Access the menu Modules, select AutoGrid and confirm "yes" to enter AutoGrid™ v8. You’re now ready to start the grid generation process and mesh the bypass configuration!
Tutorials
3-3
Bypass Configuration
Mesh Generation
AutoGrid™ v8 graphical user interface includes several windows that allow to visualize the geometry and mesh of the turbomachine simultaneously in the meridional, blade-to-blade and 3D view. The access to main menu and controls is proposed through a menu bar and a quick access pad, and is completed with a tool/icon bar. The execution of the different actions undertaken is summarized in the message box at the bottom of the interface.
3-2
Mesh Generation
A step by step approach is proposed in the following lines. It aims at driving you through the various steps that need to be executed from the creation of the mesh project to the validation of the final mesh quality.
3-2.1 1.
Create Mesh Project Close the Open Turbo Project Wizard dialog box The Open Turbo Project Wizard dialog box enables the user to retrieve a ".trb" file (with associated grid) including the data required to regenerate a mesh on an identical or similar geometry. In this tutorial, these data will be progressively introduced based on the geometry of the project case.
2.
Go to menu File -> New Project
3.
Click yes to close the active project
4.
Choose the icon Initialize a New Project from a geomTurbo File
3-2.2 5.
Load Geometry & Define Main Properties Locate and select bypass.geomTurbo (geometry defined in [Millimeter]) in the dialog box and click Open The ".geomTurbo" file format is structured in three main blocks: the header, the channel and the row(s) definitions.
3-4
Tutorials
Mesh Generation
Bypass Configuration
The channel format contains the definition of the turbomachinery meridional contour (hub, shroud and nozzle). It is composed by curves defined by a set of points. The ".geomTurbo" file must contain two channel curves named respectively "hub" and "shroud". In addition when meshing a bypass configuration, the nozzle must be defined.
shroud
… …
OUTLET
INLET hub
…
nozzle
The nozzle must be defined from the outlet down bypass to the outlet up bypass
The row definition contains the geometry of a complete row. The blade and splitter are defined by the pressure and the suction side surfaces identified by the keywords "pressure" and "suction". Both surfaces are specified by a set of cross sections of the blade at several spanwise location from hub to shroud. Each section is defined by a set of points from leading to trailing edge.
Row defined in front of nozzle
Row defined in up bypass
Row defined in down bypass
Tutorials
3-5
Bypass Configuration
Mesh Generation
The geometry can also be imported through a graphic window (Geometry Import and Link CAD) when defining a new project from Definition scratch with bypass. When click-right in the graphic window, a pop-up menu allows the user to define the nozzle in addition of the hub and shroud. In addition row on nozzle and in up/down bypass can be added in the configuration.
Warning may prompt if one of the rows is not intersecting the hub and/or he shroud.
The warning inform the user that the row 3 needs to be extended to intersect the hub.
6.
Click-left on Ok
7.
Click-left on Rows Definition
8.
Click-right on Main Blade to get the contextual menu and select Expand Geometry
9.
Select Hub treatment/expand
row 3
Blades
Main Blade
• Set Expansion Factor to
3-6
Tutorials
Mesh Generation
Bypass Configuration
• Apply to extend the blade
10. Click-left 11.
on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active it
Click-right on row 1 and select Properties in the pop-up menu
12. Enter 13. Enter
the Periodicity (number of blades) to in Rotation Speed (rpm) The speed will be transferred to FINE™ graphical user interface and ease the input of boundary conditions later on. The sign of the rotational speed is positive (+) when the blade row is rotating in the positive θ direction, and negative otherwise
14. Select
Rotor as a row type and Axial as a row orientation
The row type and row orientation settings are only information that will not impact or control the mesh generation process. 15. Activate
Default in order to plot the full turbomachine in 3D view when selecting View/ toggle 3D Solid View
16. Execute
the same operations for the elements row2, row3, row4 and row5, defined respectively by the following parameters as --Stator-Axial, --Stator-Axial, --Rotor-Axial and --Stator-Axial (it is not necessary to close the dialog box each time)
17. Close
Tutorials
the dialog box
3-7
Bypass Configuration
Mesh Generation
18. Click-left
on Rows Definition -> row 1
19. Click-right 20. Keep
21. Define
Width At Trailing Edge = [Millimeters]
22. Click-left
on Rows Definition -> row 3 and row 5
23. Click-right
and select Define Hub Gap in the pop-up menu
24. Define
Width At Leading Edge = [Millimeters]
25. Define
Width At Trailing Edge = [Millimeters]
26. Click-left
3-8
and select Define Shroud Gap in the pop-up menu
Width At Leading Edge = [Millimeters]
on Rows Definition -> row 4
Tutorials
Mesh Generation
Bypass Configuration
27. Click-right
and select Define Shroud Gap in the pop-up menu
28. Define
Width At Leading Edge = [Millimeters]
29. Define
Width At Trailing Edge = [Millimeters]
The width at leading/trailing edge allows to specify the size of the gap respectively at the leading and trailing edge of the blade. The gap curve is then constructed as a linear offset of the hub (or the shroud) according to these values. 30. Set
the scaling factor
• Go to Geometry Definition Units • Change the units to Millimeters
The "units" of the imported geometry must be changed to impose a scaling factor and a corresponding tolerance that will ensure correct treatment during the grid generation when computing for example the intersection. If not necessary, we recommend to keep the default settings (Scale Factor set to 1) 31. Click-left
on Select All Rows
32. Select
toggle 3D Solid View in the View menu to access the shaded blades in 3D view
33. Select
toggle 3D Solid View in the View menu to remove the shaded blades in 3D view
3-2.3
Set Default Topology
34. Click-left 35. Select
on Select All Rows
Grid Level/Medium through Mesh Control in Quick Access Pad
36. Estimate
the width of the first cell at the wall:
The width of the first cell close to the wall must be selected with care since the quality of the flow solution will often depend upon the capture of the flow phenomena inside the boundary layers which develop along the solid walls. Depending upon the turbulence model selected, NUMECA recommends to locate the nearest grid point along the wall, at a distance that corresponds to
Tutorials
3-9
Bypass Configuration
Mesh Generation
parietal coordinate y+ ranging from 1-5 (low Reynolds number models) or 3050 (high Reynolds number models). Assuming thermal effects must be modelled accurately, y+ can reach values as low as 0.1. The relation between the parietal coordinate y+ and width of the first cell close to the wall y is driven by the Blasius equation, expressed as follows for turbulent flows:
where: - ywall is the distance of the nearest grid point to the wall (in meter); - Vref is a reference velocity of the flow, for instance the inlet velocity (in m/s); - υ is the kinematic viscosity of the fluid (in m2/s), i.e. the dynamic viscosity divided by the density; - Lref is a reference length of the test case (in meter); - y+ is a non-dimensional value. Input the value of the Cell Width = [Millimeters] in Row Mesh Control.
37. Select
(Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology
The default skin-topology includes 5 blocks as follows: - the skin block is a O-mesh surrounding the blade
3-10
Tutorials
Mesh Generation
Bypass Configuration
- the inlet block is a H-mesh located upstream the leading edge - the outlet block is a H-mesh located downstream the trailing edge - the up block is a H-mesh located above the blade section - the down block is a H-mesh located under the blade section
3-2.4
Meridional Control When overlapping detected in the flow paths, a warning is appearing at the bottom of the graphical user interface. In addition, the expansion ratio is plotted in the message box.
38. Check
quality of the flow paths
• Click-left in meridional view to activate it (red border) • Click-left on • Select quality criteria using the Type pull-down menu • Click-left on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn for each row
• Click-left on part of the histogram to plot the concerned cells in the meridional view • Click-left on More info button to obtain information about minimum and maximum values of the selected criteria
• Close dialog box
Click Left
39. Control
bypass and nozzle points distributions
• Click-left on Select All Rows • Click-left on Mesh Control -> Row Mesh Control -> Flow Paths Control -> Expert • Deactivate View Flow Path to plot the grid used to generate the flow paths
Tutorials
3-11
Bypass Configuration
Mesh Generation
• Close dialog box
3-2.4.1 Bypass - Nozzle Control • Click-left on • Click-left on double arrow when highlighted in red, type to control the points distribution on nozzle and to remove overlapping cells
• Click-left on Select All Rows • Click-left on Generate Flow Paths
Click Left
• Click-left on thickness (0.3%), type to increase the thickness of the C-block covering the nozzle
• Click-left on Select All Rows • Click-left on Generate Flow Paths
3-12
Tutorials
Mesh Generation
Bypass Configuration
Click Left
Click-left on the number of nodes, make the proper modification in the entry box and press to confirm the modification. Nozzle flow paths index and nozzle cell width can also be imposed. H-topology on nozzle is adapted for bypass configuration presenting a sharp nozzle.
40. Adapt
• • • •
control lines close to nozzle
Click-left on control line defining the nozzle topology when highlighted in yellow Click-left on control point defining the control line Move control point at desired location Click-left on control point to validate its new location
Click Left
The exact coordinates of the control points can also be introduced with clickright on the control point; a dialog box appears, enabling the user to enter the point coordinates in (rz) mode.
• Click-right on control line defining the nozzle topology when highlighted in yellow • Select Properties • Set the Cell width respectively to and The same cell width has to be imposed on both control lines defining the nozzle.
Tutorials
3-13
Bypass Configuration
Mesh Generation
• Set the streamwise number of points (Streamwise Npts) respectively to and
1.0
• Click-left on Select All Rows • Click-left on Generate Flow Paths
3-2.4.2 Copy/Paste Flow Paths Distribution • • • •
Click-right on the outlet of the up bypass when highlighted in yellow Select Copy Left Distribution Click-right on the rotor/stator of the up bypass when highlighted in yellow Select Paste Right Distribution
C --> R
Copy/Paste are used to copy a distribution from a rotor/stator to another one or to a meridional control line. Merge is used to compute a common distribution from the left and right distributions at a rotor/stator. It is created for rotor/stators where the left row has a hub gap and the right row a shroud gap (or the opposite). Clear is used to clean copy/merge operations on selected control line.
• Click-left on Select All Rows • Click-left on Generate Flow Paths
3-14
Tutorials
Mesh Generation
Bypass Configuration
Along the down bypass, automatic copy/paste and merge flow paths distributions are performed.
M
M
C --> R
C --> L
3-2.4.3 Bulb Control The configuration is presenting a hub defined with a control point at R=0. A bulb is automatically detected and flow paths controls are added. 41. Adapt
• • • •
control line close to the bulb
Click-left on control line when highlighted in yellow Click-left on control point defining the control line Move control point at desired location Click-left on control point to validate its new location
Click Left
• Click-left on Select All Rows • Click-left on Generate Flow Paths 42. Adapt
flow paths distribution in bulb
• Click-left on • Deactivate Singular line to impose a butterfly topology in the bulb Three topologies are available for bulbs: sharp (H-mesh), rounded (C-mesh) or radial. With C mesh, the zero radius area can be meshed with a singular line or a butterfly topology. Butterfly topology
Singular line
Tutorials
3-15
Bypass Configuration
Mesh Generation
Click-left on the number of nodes, make the proper modification in the entry box and press to confirm the modification.
• Close dialog box • Click-left on Select All Rows • Click-left on Generate Flow Paths 43. Check
3-2.5
quality of the flow paths as presented in step 38
Blade-to-Blade Control
44. Click
on Generate B2B
row 4
row 1
row 3
row 5
When plotting all rows on hub (active layer set 0% by default), the row 2 is not appearing in the blade-to-blade view because it is not intersecting the hub. To check the mesh on row 2, an active layer intersecting the row 2 should be selected.
3-16
Tutorials
Mesh Generation
Bypass Configuration
45. Go
to Mesh Control
Row Mesh Control
B2B Mesh Topology Control
Topology
By default, non-matching connections are applied at periodic boundaries. Matching connections at periodic boundaries can be obtained by activating the Matching Periodicity check button. Press Re(set) Default Topology to regenerate the mesh in the blade-to-blade plane. In most cases, the presence of non-matching connections somehow improves the orthogonality in the overall mesh. This is especially true in highly staggered configurations. 46. Keep
Matching Periodicity deactivated and all other data identical In several turbomachinery types, the blades are highly staggered (Automatic High Staggered Blade Detection within AutoGrid™). If the solid angle at the inlet (outlet) of the machine becomes greater than 450 and if the location of the inlet (outlet) limits of the domain is close to the leading edge (trailing edge) of the blades, then the default topology is not suitable anymore since the cells located near the inlet (outlet) boundary become very skewed. To improve this unexpected behaviour, AutoGrid™ uses the High Staggered Blade Optimization.
47. Deactivate
Topology option
48. Go
to Mesh Control Row Mesh Control B2B Mesh Topology Control -> Grid Points to control the number of grid points in the blade-to-blade view if necessary
49. Click-left on
the number of nodes, make the proper modification in the entry box and press to confirm the modification
The number of points specified is recommended to be 4xn + 1 (where n is an integer) to allow multigrid process on minimum 3 grid levels within FINE™.
Tutorials
3-17
Bypass Configuration
Mesh Generation
50. Visualize
the result in blade-to-blade view after selecting Generate B2B to regenerate the flow paths and the mesh in blade-to-blade plane.
51. Deactivate 52. Close
Grid Points option
the dialog box.
to Mesh Control -> Active B2B Layer to specify the flow path (layer) on which the blade-to-blade mesh will be plotted in the blade-to-blade view
53. Go
By default, the active layer is the hub of the machine (Active Layer (%span) set to 0). The layer selected for visualization is defined in percentage of span, going from hub (0%) to shroud (100%) and is applied on active row(s). 54. Click-left 55. Enter
on Select All Rows
for example in order to visualize the mesh at 50% span
56. Select
Generate B2B to regenerate the blade-to-blade mesh on new specified layer in the blade-to-blade view Detailed analysis of mesh quality can be performed on Blade-to-Blade mesh after generation. Information on orthogonality, aspect ratio and expansion ratio can be outlined in this window using the Type pull-down menu and plotted in the blade-to-blade view on active layer selected in Mesh Control/ Active B2B Layer.
57. Check
for grid quality by clicking on
58. Select
quality criteria using the Type pull-down menu
59. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn for each row
60. Click-left
on part of the histogram to plot the concerned cells in the blade-to-blade view
61. Click-left on
More info button to obtain information about minimum and maximum values of the selected criteria
Click Left
3-18
Tutorials
Mesh Generation
Bypass Configuration
62. Close
the dialog box
63. Go to Mesh Control ->
Row Mesh Control -> Optimization Control to adapt the mesh optimization parameters if necessary to enhance the quality of the mesh
Optimization is performed in the form of smoothing and is executed on each layer using multi-block elliptic techniques. The number of Optimization Steps represents the number of iterations performed with the elliptic smoother. By default, 100 iterations are applied. 64. Keep
default Optimization Steps and all other data identical
65. Close
the dialog box
3-2.6
3D Mesh Generation
66. Click-left 67. Click
Tutorials
on Select All Rows
on the icon Generate 3D and confirm the generation
3-19
Bypass Configuration
Mesh Generation
Once 3D grid generation is completed, grid quality is performed and displayed. Minimum cells skewness, the maximum expansion ratio and aspect ratio are reported, among others. Data are available for the entire mesh separately for every entity (row, technological effect, bulb). Data related to grid quality report are automatically stored in a report file, once the project file is saved. 68. Close
3-2.7
the dialog box. This page can also be reopened by clicking on
3D Mesh Visualization
69. Click-left 70. Select
on Select All Rows
View/toggle 3D Solid View to access the shaded blades in 3D view
71. Click-left
in 3D view; the Quick Access Pad (QAP) is modified
72. Click-right 73.
3-2.8
Use View menu in QAP or View/Patch Viewer... menu to toggle edge or mesh
Check Boundary Conditions & Mesh Quality
74. Check
3-20
to get the contextual menu and activate Full View
for boundary conditions by clicking on
Tutorials
Mesh Generation
Bypass Configuration
75. Select
UND under Type pull-down menu and check that no patches are in the patch list still set with an undefined type
It is important to make sure that no undefined patches (UND) are present in the mesh. In that case, these can usually be removed by increasing the tolerance and launching the Search procedure. 76. Close
the dialog box
77. Check
for negative cells by clicking on
78. Click
on Apply The computation of the negative volumes is performed first. Negative cells can be outlined in the mesh pushing View neg cells button. Beware that the visualization of negative cells can be memory consuming when a large number of cells must be displayed. It is then advised to first check the number of negative cells by pressing the Apply button. It is mandatory to remove all negative cells before the calculation can be started.
Tutorials
79. Close
the dialog box
80. Check
for grid quality by clicking on
3-21
Bypass Configuration
Mesh Generation
Detailed analysis of mesh quality on 3D mesh (in blocks, at boundaries and at FNMB) can be performed only once the 3D mesh has been generated. Information on orthogonality, angular deviation, aspect ratio, expansion ratio and cell width can be outlined in this window using the Type pull-down menu. 81. Select
quality criteria using the Type pull-down menu
82. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn per block (0 = all blocks)
83. Click-left
on part of the histogram to plot the concerned cells in the 3D view
Click Left
84. Click-left on
More info button to obtain information about minimum and maximum values of the selected criteria
85. Close
3-2.9 86.
the dialog box
Save Project Go to File -> Save Project As to save mesh and template files The mesh files (7 files) contain the multiblock mesh topology, geometry and grid points and the boundary condition types: ".bcs", ".cgns", ".geom" (".xmt_txt"), ".igg", ".config" and ".qualityReport".The meaning of these files is detailed in the user manual. The template files (4 files) contain the parameters and the geometry needed to reproduced the mesh with AutoGrid™: ".geomTurbo" (".geomTurbo.xmt_txt"), ".trb" and ".info". The meaning of these files is detailed in the user manual.
3-22
Tutorials
TUTORIAL 4:
Tandem Row
4-1
Introduction
4-1.1
Introduction
The resolution of computational fluid dynamics (CFD) problems involves three main steps:
• spatial discretization of the flow equations • flow computation • visualization of the results To answer these questions, NUMECA has developed a Flow INtegrated Environment for internal and Turbomachinery assimilations. Called FINE™/Turbo, the environment integrates the following tools:
• IGG™ is an Interactive Geometry modeler and Grid generator software, based on structured multi-block techniques
• AutoGrid™ is a three-dimensional Automated Grid generation software, dedicated to turbomachinery applications. Similarly to IGG™, it is based on structured multi-block techniques
• Euranus is a state-of-the-art multi-block flow solver, able to simulate Euler and Navier-Stokes equations in the laminar, transitional and turbulent regimes
• CFView™ is a highly interactive flow visualization and post-treatment software • FINE™ Graphical User Interface is a user-friendly environment that includes the different softwares. It integrates the concept of projects and allows the user to achieve complete simulations, going from the grid generation to the flow visualization, without the need of file manipulation A turbomachine is a device in which the energy is transferred either to or from a continuously flowing fluid by the dynamic action of one or more moving blade rows. It plays a major role in particular in aircraft, marine space (liquid rockets), land propulsion system but also in hydraulic, gas and steam turbines applications. It is also involved in industrial pipeline and processing equipment such as gas, petroleum and water pumping plants. Other applications can be related to heart-assist pumps, industrial compressors and refrigeration plants, among others. The turbomachinery field includes turbines, pumps, fans, compressors. A turbomachine is composed of several basic elements including the blade (also called vane if it is non-rotating), hub, and shroud. Several technological effects involving clearances, seal leakages and cooling holes among
Tutorials
4-1
Tandem Row
Introduction
others can complete the machine. Due to the complexity of the blade shapes, the presence of technological elements and the rotation of machine, the nature of the flow is strongly three-dimensional, often depicting complex flow paths. This tutorial is particularly adapted to the mesh generation of tandem row configuration. It makes exclusive use of AutoGrid™ v8 and describes the main actions required to mesh the configuration of interest. In this tutorial you will learn how to:
• • • •
4-1.2
Read an existing geometrical file into AutoGrid™ v8; Define a tandem row; Control the blade-to-blade mesh; Control the quality of the mesh in the blade-to-blade and 3D mesh.
Prerequisites
This tutorial does not require any particular prerequisite but it is strongly recommended for beginners to perform the basic tutorials 1 to 7.
4-1.3
Problem Description
The problem to be considered is shown schematically here below (meridional view). The project consists in the mesh generation of a tandem row configuration (part of an airplane engine). The configuration consists in a single row composed by a main blade and a splitter without overlap in the streamwise direction.
4-1.4
Preparation
• Copy the files located in cdrom:\DOC\_Tutorials\AutoGrid\_advanced\Tutorial_4 to your working directory, where cdrom must be replaced by the name of your DVD-ROM.
• Start AutoGrid™ v8.x
4-2
Tutorials
Introduction
Tandem Row
For LINUX and UNIX systems, you can access AutoGrid™ v8.x graphical user interface with the following command line igg -niversion 8x -print or igg -niversion autogrid8x -print For WINDOWS systems, you can access AutoGrid™ v8.x graphical user interface from the start menu going to /Programs/NUMECA software/fine8x/IGG or /Programs/NUMECA software/autogrid8x/IGG
4
• Access the menu Modules, select AutoGrid and confirm "yes" to enter AutoGrid™ v8. You’re now ready to start the grid generation process and mesh the tandem configuration!
Tutorials
4-3
Tandem Row
Mesh Generation
AutoGrid™ v8 graphical user interface includes several windows that allow to visualize the geometry and mesh of the turbomachine simultaneously in the meridional, blade-to-blade and 3D view. The access to main menu and controls is proposed through a menu bar and a quick access pad, and is completed with a tool/icon bar. The execution of the different actions undertaken is summarized in the message box at the bottom of the interface.
4-2
Mesh Generation
A step by step approach is proposed in the following lines. It aims at driving you through the various steps that need to be executed from the creation of the mesh project to the validation of the final mesh quality.
4-2.1 1.
Create Mesh Project Close the Open Turbo Project Wizard dialog box The Open Turbo Project Wizard dialog box enables the user to retrieve a ".trb" file (with associated grid) including the data required to regenerate a mesh on an identical or similar geometry. In this tutorial, these data will be progressively introduced based on the geometry of the project case.
2.
Go to menu File -> New Project
3.
Click yes to close the active project
4.
Choose the icon Initialize a New Project from a geomTurbo File
4-2.2 5.
Load Geometry & Define Main Properties Locate and select tandem.geomTurbo (geometry defined in [Millimeter]) in the dialog box and click Open The ".geomTurbo" file format is structured in three main blocks: the header, the channel and the row(s) definitions. The channel format contains the definition of the turbomachinery meridional contour (hub and shroud). It is composed by curves defined by a set of points. The ".geomTurbo" file must contain two channel curves named respectively "hub" and "shroud".
4-4
Tutorials
Mesh Generation
Tandem Row
The tandem configuration is defined by a single row composed by a main blade and a splitter downstream the main blade without overlap in the streamwise direction. The row definition contains the geometry of a complete row. The main blade and splitter are defined by the pressure and the suction side surfaces identified by the keywords "pressure" and "suction". Both surfaces are specified by a set of cross sections of the blade at several spanwise location from hub to shroud. Each section is defined by a set of points from leading to trailing edge.
INLET
OUTLET
Main Blade
Splitter 1
The geometry can also be imported through a graphic window (Geometry Definition Import and Link CAD) when defining a new project from scratch. When click-right in the graphic window, a pop-up menu allows the user to define the hub, shroud and to link the surfaces, trailing and leading edge curves to the selected blade in the Rows Definition (Main Blade or Splitter 1). When click-right on row 1 in Rows Definition, a menu allows the user to add a blade (splitter) in the selected row;
Tutorials
6.
Click-left on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active it
7.
Click-right on row 1 and select Properties in the pop-up menu
8.
Keep the Periodicity (number of blades) to
9.
Keep in Rotation Speed (rpm)
4-5
Tandem Row
Mesh Generation
The speed will be transferred to FINE™ graphical user interface and ease the input of boundary conditions later on. The sign of the rotational speed is positive (+) when the blade row is rotating in the positive θ direction, and negative otherwise 10. Select
Rotor as a row type and Axial as a row orientation
The row type and row orientation settings are only information that will not impact or control the mesh generation process. 11.
Activate Tandem Row in order to set automatically the grid points distribution of the blade to blade mesh when setting the default topology
12. Activate
Default in order to plot the full turbomachine in 3D view when selecting View/ toggle 3D Solid View
13. Close
the dialog box
14. Click-left
4-6
on Select All Rows
15. Select
toggle 3D Solid View in the View menu to access the shaded blades in 3D view
16. Select
toggle 3D Solid View in the View menu to remove the shaded blades in 3D view
Tutorials
Mesh Generation
4-2.3
Tandem Row
Set Default Topology
17. Click-left 18. Select
on Select All Rows
Grid Level/Medium through Mesh Control in Quick Access Pad
19. Estimate
the width of the first cell at the wall:
The width of the first cell close to the wall must be selected with care since the quality of the flow solution will often depend upon the capture of the flow phenomena inside the boundary layers which develop along the solid walls. Depending upon the turbulence model selected, NUMECA recommends to locate the nearest grid point along the wall, at a distance that corresponds to parietal coordinate y+ ranging from 1-5 (low Reynolds number models) or 3050 (high Reynolds number models). Assuming thermal effects must be modelled accurately, y+ can reach values as low as 0.1. The relation between the parietal coordinate y+ and width of the first cell close to the wall y is driven by the Blasius equation, expressed as follows for turbulent flows:
where: - ywall is the distance of the nearest grid point to the wall (in meter); - Vref is a reference velocity of the flow, for instance the inlet velocity (in m/s); - υ is the kinematic viscosity of the fluid (in m2/s), i.e. the dynamic viscosity divided by the density; - Lref is a reference length of the test case (in meter); - y+ is a non-dimensional value. Input the value of the Cell Width = [Millimeters] in Row Mesh Control.
Tutorials
4-7
Tandem Row
Mesh Generation
20. Select
(Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology
The default skin-topology includes 5 blocks for each blade as follows: - the skin block is a O-mesh surrounding the blade - the inlet block is a H-mesh located upstream the leading edge - the outlet block is a H-mesh located downstream the trailing edge - the up block is a H-mesh located above the blade section - the down block is a H-mesh located under the blade section
Down Splitter 1 Inlet Splitter 1
Inlet Main Blade
Up Main Blade Up Splitter 1 Skin Splitter 1 Skin Main Blade
Down Main Blade
Outlet Splitter 1
Outlet Main Blade
4-2.4
Meridional Control
21. Go
to QAP Mesh Control
22. Keep
the number of flow path as
flow paths if necessary through Mesh Control -> Row Mesh Control -> Flow Paths Control
23. Control
4-8
24. Keep
data identical
25. Close
the dialog box
Tutorials
Mesh Generation
Tandem Row
4-2.5
Blade-to-Blade Control
26. Click-left
on main blade or splitter mesh in the blade-to-blade view
27. Go
to Mesh Control Topology
Row Mesh Control
B2B Mesh Topology Control
By default, when tandem row is specified, matching connections (Matching Periodicity check button active) are applied at periodic boundaries and at connection between main blade and splitter.
Main Blade
Matching Connection
Splitter 1
28. Keep
Matching Periodicity activated and all other data identical for main blade and split-
ter In several turbomachinery types, the blades are highly staggered (Automatic High Staggered Blade Detection within AutoGrid™). If the solid angle at the inlet (outlet) of the machine becomes greater than 450 and if the location of the inlet (outlet) limits of the domain is close to the leading edge (trailing edge) of the blades, then the default topology is not suitable anymore since the cells located near the inlet (outlet) boundary become very skewed. To improve this unexpected behaviour, AutoGrid™ uses the High Staggered Blade Optimization. 29. Deactivate
Topology option
30. Go
to Mesh Control Row Mesh Control B2B Mesh Topology Control -> Grid Points to control the number of grid points in the blade-to-blade view if necessary.
Tutorials
4-9
Tandem Row
Mesh Generation
By default, when tandem row is specified, the grid points distribution along the main blade and splitter will be adapted as presented on figure below. Splitter 1 N4
N5
N6
Main Blade N1
N2
N3 N4 = N1 + N2 N3 = N5 + N6
31. Click-left on
the number of nodes, make the proper modification in the entry box and press to confirm the modification The number of points specified is recommended to be 4xn + 1 (where n is an integer) to allow multigrid process on minimum 3 grid levels within FINE™. When tandem row is specified, to keep matching connections at periodic boundaries and at connection between main blade and splitter: + if the grid points distribution N1 and/or N2 is modified along main blade, N4 along splitter 1 has to be adapted accordingly; + if the grid points distribution N3 is modified along main blade, N5 and/or N6 along splitter 1 has to be adapted accordingly; + if the grid points distribution N4 is modified along splitter 1, N1 and/or N2 along main blade has to be adapted accordingly; + if the grid points distribution N5 and/or N6 is modified along splitter 1, N3 along main blade has to be adapted accordingly. Main Blade
Splitter 1
N2 ↑ N5 ↑
4-10
⇒ N4 ↑ ⇒ N3 ↑ Tutorials
Mesh Generation
Tandem Row
32. Visualize
the result in blade-to-blade view after selecting Generate B2B to regenerate the flow paths and the mesh in blade-to-blade plane
33. Deactivate 34. Close
Grid Points option
the dialog box.
to Mesh Control -> Active B2B Layer to specify the flow path (layer) on which the blade-to-blade mesh will be plotted in the blade-to-blade view
35. Go
By default, the active layer is the hub of the machine (Active Layer (%span) set to 0). The layer selected for visualization is defined in percentage of span, going from hub (0%) to shroud (100%) and is applied on active row(s). 36. Click-left 37. Enter
on Select All Rows
for example in order to visualize the mesh at 50% span
38. Select
Generate B2B to regenerate the blade-to-blade mesh on new specified layer in the blade-to-blade view Detailed analysis of mesh quality can be performed on Blade-to-Blade mesh after generation. Information on orthogonality, aspect ratio and expansion ratio can be outlined in this window using the Type pull-down menu and plotted in the blade-to-blade view on active layer selected in Mesh Control/ Active B2B Layer.
39. Click-left 40. Go
on the blade-to-blade window to activate that view (red border)
to the menu View-> Repetition
41. Increase
Nb Repet to and Show
42. Close
the dialog box
43. Check
for grid quality by clicking on
44. Select
quality criteria using the Type pull-down menu
45. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn for each row
46. Click-left
on part of the histogram to plot the concerned cells in the blade-to-blade view
47. Click-left on
More info button to obtain information about minimum and maximum values of the selected criteria
48. Close
Tutorials
the dialog box
4-11
Tandem Row
Mesh Generation
Click Left
49. Go to Mesh Control ->
Row Mesh Control -> Optimization Control to adapt the mesh optimization parameters if necessary to enhance the quality of the mesh
Optimization is performed in the form of smoothing and is executed on each layer using multi-block elliptic techniques. The number of Optimization Steps represents the number of iterations performed with the elliptic smoother. By default, 100 iterations are applied. 50. Keep
default Optimization Steps and all other data identical
51. Close
the dialog box
4-2.6
3D Mesh Generation
52. Click-left 53. Click
4-12
on Select All Rows
on the icon Generate 3D and confirm (Start) the generation
Tutorials
Mesh Generation
Tandem Row
Once 3D grid generation is completed, grid quality is performed and displayed. Minimum cells skewness, the maximum expansion ratio and aspect ratio are reported, among others. Data are available for the entire mesh separately for every entity (row, technological effect, bulb). Data related to grid quality report are automatically stored in a report file, once the project file is saved.
54. Close
4-2.7
the dialog box. This page can also be reopened by clicking on
3D Mesh Visualization
55. Click-left 56. Select
on Select All Rows
View/toggle 3D Solid View to access the shaded blades in 3D view
57. Click-left
in 3D view; the Quick Access Pad (QAP) is modified
58. Click-right 59.
Tutorials
to get the contextual menu and activate Full View
Use View menu in QAP or View/Patch Viewer... menu to toggle edge or mesh
4-13
Tandem Row
Mesh Generation
4-2.8
Check Boundary Conditions & Mesh Quality
60. Check
for boundary conditions by clicking on
61. Select
UND under Type pull-down menu and check that no patches are in the patch list still set with an undefined type
4-14
Tutorials
Mesh Generation
Tandem Row
It is important to make sure that no undefined patches (UND) are present in the mesh. In that case, these can usually be removed by increasing the tolerance and launching the Search procedure. 62. Close
the dialog box
63. Check
for negative cells by clicking on
64. Click
on Apply The computation of the negative volumes is performed first. Negative cells can be outlined in the mesh pushing View neg cells button. Beware that the visualization of negative cells can be memory consuming when a large number of cells must be displayed. It is then advised to first check the number of negative cells by pressing the Apply button. It is mandatory to remove all negative cells before the calculation can be started.
65. Close
the dialog box
66. Check
for grid quality by clicking on
Detailed analysis of mesh quality on 3D mesh (in blocks, at boundaries and at FNMB) can be performed only once the 3D mesh has been generated. Information on orthogonality, angular deviation, aspect ratio, expansion ratio and cell width can be outlined in this window using the Type pull-down menu.
Click Left
Tutorials
4-15
Tandem Row
Mesh Generation
67. Select
quality criteria using the Type pull-down menu
68. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn per block (0 = all blocks)
69. Click-left
on part of the histogram to plot the concerned cells in the 3D view
70. Click-left on
More info button to obtain information about minimum and maximum values of the selected criteria
71. Close
4-2.9 72.
the dialog box
Save Project Go to File -> Save Project As to save mesh and template files The mesh files (7 files) contain the multiblock mesh topology, geometry and grid points and the boundary condition types: ".bcs", ".cgns", ".geom" (".xmt_txt"), ".igg", ".config" and ".qualityReport".The meaning of these files is detailed in the user manual. The template files (4 files) contain the parameters and the geometry needed to reproduced the mesh with AutoGrid™: ".geomTurbo" (".geomTurbo.xmt_txt"), ".trb" and ".info". The meaning of these files is detailed in the user manual.
4-16
Tutorials
TUTORIAL 5:
Cascade Configuration
5-1
Introduction
5-1.1
Introduction
The resolution of computational fluid dynamics (CFD) problems involves three main steps:
• spatial discretization of the flow equations • flow computation • visualization of the results To answer these questions, NUMECA has developed a Flow INtegrated Environment for internal and Turbomachinery assimilations. Called FINE™/Turbo, the environment integrates the following tools:
• IGG™ is an Interactive Geometry modeler and Grid generator software, based on structured multi-block techniques
• AutoGrid™ is a three-dimensional Automated Grid generation software, dedicated to turbomachinery applications. Similarly to IGG™, it is based on structured multi-block techniques
• Euranus is a state-of-the-art multi-block flow solver, able to simulate Euler and Navier-Stokes equations in the laminar, transitional and turbulent regimes
• CFView™ is a highly interactive flow visualization and post-treatment software • FINE™ Graphical User Interface is a user-friendly environment that includes the different softwares. It integrates the concept of projects and allows the user to achieve complete simulations, going from the grid generation to the flow visualization, without the need of file manipulation A turbomachine is a device in which the energy is transferred either to or from a continuously flowing fluid by the dynamic action of one or more moving blade rows. It plays a major role in particular in aircraft, marine space (liquid rockets), land propulsion system but also in hydraulic, gas and steam turbines applications. It is also involved in industrial pipeline and processing equipment such as gas, petroleum and water pumping plants. Other applications can be related to heart-assist pumps, industrial compressors and refrigeration plants, among others. The turbomachinery field includes turbines, pumps, fans, compressors. A turbomachine is composed of several basic elements including the blade (also called vane if it is non-rotating), hub, and shroud. Several technological effects involving clearances, seal leakages and cooling holes among
Tutorials
5-1
Cascade Configuration
Introduction
others can complete the machine. Due to the complexity of the blade shapes, the presence of technological elements and the rotation of machine, the nature of the flow is strongly three-dimensional, often depicting complex flow paths. This tutorial is particularly adapted to the mesh generation of cascade configuration. It makes exclusive use of AutoGrid™ v8 and describes the main actions required to mesh the configuration of interest. In this tutorial you will learn how to:
• • • •
Read an existing geometrical file into AutoGrid™ v8; Define cascade configuration; Control the meridional and blade-to-blade mesh; Control the quality of the mesh in the blade-to-blade and 3D mesh.
5-1.2
Prerequisites
This tutorial does not require any particular prerequisite but it is strongly recommended for beginners to perform the basic tutorials 1 to 7.
5-1.3
Problem Description
The problem to be considered is shown schematically here below. The project consists in the mesh generation of the T106 turbine blade cascade configuration.
5-1.4
Preparation
• Copy the files located in cdrom:\DOC\_Tutorials\AutoGrid\_advanced\Tutorial_5 to your working directory, where cdrom must be replaced by the name of your DVD-ROM.
• Start AutoGrid™ v8.x For LINUX and UNIX systems, you can access AutoGrid™ v8.x graphical user interface with the following command line igg -niversion 8x -print or igg -niversion autogrid8x -print
5-2
Tutorials
Introduction
Cascade Configuration
For WINDOWS systems, you can access AutoGrid™ v8.x graphical user interface from the start menu going to /Programs/NUMECA software/fine8x/IGG or /Programs/NUMECA software/autogrid8x/IGG
4
• Access the menu Modules, select AutoGrid and confirm "yes" to enter AutoGrid™ v8. You’re now ready to start the grid generation process and mesh the cascade configuration!
AutoGrid™ v8 graphical user interface includes several windows that allow to visualize the geometry and mesh of the turbomachine simultaneously in the meridional, blade-to-blade and 3D view. The access to main menu and controls is proposed through a menu bar and a quick access pad, and is completed with a tool/icon bar. The execution of the different actions undertaken is summarized in the message box at the bottom of the interface.
Tutorials
5-3
Cascade Configuration
5-2
Mesh Generation
Mesh Generation
A step by step approach is proposed in the following lines. It aims at driving you through the various steps that need to be executed from the creation of the mesh project to the validation of the final mesh quality.
5-2.1 1.
Create Mesh Project Close the Open Turbo Project Wizard dialog box The Open Turbo Project Wizard dialog box enables the user to retrieve a ".trb" file (with associated grid) including the data required to regenerate a mesh on an identical or similar geometry. In this tutorial, these data will be progressively introduced based on the geometry of the project case.
2.
Go to menu File -> New Project
3.
Click yes to close the active project
4.
Activate Cascade option
5.
Choose the icon Start a New Project From Scratch
5-2.2
Load Geometry & Define Main Properties
6.
Click-left row1 in Rows Definition the current row
7.
Click-left in the meridional view
8.
Go to Geometry Definition
row 1 in the Quick Access Pad (QAP) to activate
Import and Link CAD
Graphic window opens, allowing geometry import. 9.
Click-left on File
10. Select 11.
Open...
cascade.dat file from the file chooser
Define the geometry orientation if necessary
• Select Geometry Axis... in the Edit menu • Adapt origin, stream and span direction if required - keep default • Apply
5-4
Tutorials
Mesh Generation
Cascade Configuration
• Close dialog box
12. Define
the hub curve
• - click-left on all the curves defining the hub as they turn to yellow • Click-right and select Link to Hub Hub curve is displayed in the meridional view.
13. Define
the shroud curve
• - click-left on all the curves defining the shroud as they turn to yellow • Click-right and select Link to Shroud Shroud curve is displayed in the meridional view.
14. Define
the blade
• Click-left row1 in Rows Definition
row 1 in the Quick Access Pad (QAP) to activate
the current row, if not done already
Tutorials
5-5
Cascade Configuration
Mesh Generation
• Click-left on the surface defining the blade when highlighted in blue (it turns to red or yellow)
Click Left
If the blade is defined by multiple surfaces, click-middle and -click-left allow to select all the surfaces defining the blade. The View/View Solid menu acts as a toggle and allows to visualize the surfaces that are active.
• Click-right and select Link to Blade Blade is displayed in the meridional view.
15. Define
leading edge and trailing edge
• Click-left row1 in Rows Definition
row 1 in the Quick Access Pad (QAP) to activate
the current row, if not done already
• • • •
Click-left at blade leading edge line definition, inside the Import CAD window As it turns yellow, click-right and select Link to Leading Edge Click-left at blade trailing edge line definition, inside the Import CAD window As it turns yellow, click-right and select Link to Trailing Edge Leading and trailing edges are displayed in the meridional view.
5-6
Tutorials
Mesh Generation
Cascade Configuration
When blade intersects hub and shroud, inlet and outlet are displayed in the meridional view. 16. Go
to File -> Exit The geometry of the cascade configuration can also be defined from a native ".geomTurbo" file. The ".geomTurbo" file format is structured in three main blocks: the header, the channel and the row(s) definitions. The header when defining a cascade configuration should contain the keywords "cascade yes".
The channel format contains the definition of the turbomachinery meridional contour (hub and shroud). It is composed by curves defined by a set of points. The ".geomTurbo" file must contain two channel curves named respectively "hub" and "shroud". The row definition contains the geometry of a complete row. The blade is defined by the pressure and the suction side surfaces identified by the keywords "pressure" and "suction". Both surfaces are specified by a set of cross sections of the blade at several spanwise location from hub to shroud. Each section is defined by a set of points from leading to trailing edge.
Tutorials
5-7
Cascade Configuration
17. Click-left
Mesh Generation
on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active it
18. Click-right 19. Enter
on row 1 and select Properties in the pop-up menu
the Periodicity (number of blades) to The periodicity for cascade configuration corresponds to the pitch distance between two successive blades.
20. Enter
in Rotation Speed (rpm) The speed will be transferred to FINE™ graphical user interface and ease the input of boundary conditions later on.
21. Select
Stator as a row type and Axial as a row orientation
The row type and row orientation settings are only information that will not impact or control the mesh generation process.
22. Close 23. Set
the dialog box
the scaling factor
• Go to Geometry Definition Units • Change the units to Millimeters
5-8
Tutorials
Mesh Generation
Cascade Configuration
The "units" of the imported geometry must be changed to impose a scaling factor and a corresponding tolerance that will ensure correct treatment during the grid generation when computing for example the intersection. If not necessary, we recommend to keep the default settings (Scale Factor set to 1) 24. Click-left
on Select All Rows
25. Select
toggle 3D Solid View in the View menu to access the shaded blades in 3D view
26. Select
toggle 3D Solid View in the View menu to remove the shaded blades in 3D view
5-2.3
Set Default Topology
27. Click-left 28. Select
on Select All Rows
Grid Level/Medium through Mesh Control in Quick Access Pad
29. Estimate
the width of the first cell at the wall:
The width of the first cell close to the wall must be selected with care since the quality of the flow solution will often depend upon the capture of the flow phenomena inside the boundary layers which develop along the solid walls. Depending upon the turbulence model selected, NUMECA recommends to locate the nearest grid point along the wall, at a distance that corresponds to parietal coordinate y+ ranging from 1-5 (low Reynolds number models) or 3050 (high Reynolds number models). Assuming thermal effects must be modelled accurately, y+ can reach values as low as 0.1. The relation between the parietal coordinate y+ and width of the first cell close to the wall y is driven by the Blasius equation, expressed as follows for turbulent flows:
where: - ywall is the distance of the nearest grid point to the wall (in meter); - Vref is a reference velocity of the flow, for instance the inlet velocity (in m/s); - υ is the kinematic viscosity of the fluid (in m2/s), i.e. the dynamic viscosity divided by the density; - Lref is a reference length of the test case (in meter); - y+ is a non-dimensional value.
Tutorials
5-9
Cascade Configuration
Mesh Generation
Input the value of the Cell Width = [Millimeters] in Row Mesh Control.
30. Select
(Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology
The default skin-topology includes 5 blocks as follows: - the skin block is a O-mesh surrounding the blade - the inlet block is a H-mesh located upstream the leading edge - the outlet block is a H-mesh located downstream the trailing edge - the up block is a H-mesh located above the blade section - the down block is a H-mesh located under the blade section
5-2.4 31.
Meridional Control Go to QAP Mesh Control
32. Change
the number of flow path as
The number of flow path can be imposed as in order to generate a 2D mesh. flow paths if necessary through Mesh Control -> Row Mesh Control -> Flow Paths Control
33. Control
• Set Cell width at Hub as • Set Cell width at Shroud as The hub and shroud are respectively considered as a euler wall and a mirror plane. For these reasons, the cell width at hub and shroud can be increased because there are no boundary layer to capture.
5-10
Tutorials
Mesh Generation
Cascade Configuration
The Expert section allows the user to control the visualization, the shape and the parameters related to flow path smoothing. The meaning of these parameters is detailed in the user manual. The Manual Edition mode allows the user to control directly the block faces which are used to construct flow paths. Edges can be moved, segments can be created or modified and grid points distribution on segments can be controlled. More details can be found in the user manual. 34. Click
on Generate
35. Close
the dialog box
5-2.5
Blade-to-Blade Control
36. Click 37. Go
on Generate B2B
to Mesh Control Topology
Tutorials
Row Mesh Control
B2B Mesh Topology Control
5-11
Cascade Configuration
Mesh Generation
By default, non-matching connections are applied at periodic boundaries. Matching connections at periodic boundaries can be obtained by activating the Matching Periodicity check button. Press Re(set) Default Topology to regenerate the mesh in the blade-to-blade plane. In most cases, the presence of non-matching connections somehow improves the orthogonality in the overall mesh. This is especially true in highly staggered configurations. 38. Keep
Matching Periodicity deactivated and all other data identical In several turbomachinery types, the blades are highly staggered (Automatic High Staggered Blade Detection within AutoGrid™). If the solid angle at the inlet (outlet) of the machine becomes greater than 450 and if the location of the inlet (outlet) limits of the domain is close to the leading edge (trailing edge) of the blades, then the default topology is not suitable anymore since the cells located near the inlet (outlet) boundary become very skewed. To improve this unexpected behaviour, AutoGrid™ uses the High Staggered Blade Optimization.
39. Deactivate
Topology option
40. Go
to Mesh Control Row Mesh Control B2B Mesh Topology Control -> Grid Points to control the number of grid points in the blade-to-blade view if necessary
41. Click-left on
the number of nodes, make the proper modification in the entry box and press to confirm the modification
The number of points specified is recommended to be 4xn + 1 (where n is an integer) to allow multigrid process on minimum 3 grid levels within FINE™. 42. Visualize
the result in blade-to-blade view after selecting Generate B2B to regenerate the flow paths and the mesh in blade-to-blade plane.
43. Deactivate
Grid Points option
44. Close
the dialog box
45. Move
default location of leading/trailing edge:
• Click-left in blade-to-blade view to activate the view (red border) • Zoom on leading edge • When leading edge highlighted in red (move the mouse on it), click-left and drag to move the leading edge location; click-right to access a popup menu allowing to impose the points distribution at leading edge (Properties)
5-12
Tutorials
Mesh Generation
Cascade Configuration
Click Left
Click Right
Absolute Control Distance: the distance is given in absolute units and remain the same for each layer. Relative Control Distance: the distance is given in relative units (normalized with the blade width). First Cell Length: the distance is equal to the product of the cell width given by the user and the number of nodes. Another feature of this dialog box gives the control of the maximum expansion ratio of the cells in the streamwise direction along the wall. Switch on the button Desired Expansion Ratio implies that the number of grid points on the upper and lower side of the blade will be recomputed to ensure that the expansion ratio remain lower than the target value. The total number of points around the blade is then continuously updated.
• The above steps can also be applied on trailing edge • Visualize the result in blade-to-blade view after selecting Generate B2B to regenerate the flow paths and the mesh in blade-to-blade plane. to Mesh Control -> Active B2B Layer to specify the flow path (layer) on which the blade-to-blade mesh will be plotted in the blade-to-blade view
46. Go
By default, the active layer is the hub of the machine (Active Layer (%span) set to 0). The layer selected for visualization is defined in percentage of span, going from hub (0%) to shroud (100%) and is applied on active row(s). 47. Click-left 48. Enter
on Select All Rows
for example in order to visualize the mesh at 50% span
49. Select
Generate B2B to regenerate the blade-to-blade mesh on new specified layer in the blade-to-blade view
Tutorials
5-13
Cascade Configuration
Mesh Generation
Detailed analysis of mesh quality can be performed on Blade-to-Blade mesh after generation. Information on orthogonality, aspect ratio and expansion ratio can be outlined in this window using the Type pull-down menu and plotted in the blade-to-blade view on active layer selected in Mesh Control/ Active B2B Layer. 50. Check
for grid quality by clicking on
51. Select
quality criteria using the Type pull-down menu
52. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn for each row
53. Click-left
on part of the histogram to plot the concerned cells in the blade-to-blade view
54. Click-left on
More info button to obtain information about minimum and maximum values of the selected criteria
Click Left
55. Close
the dialog box
56. Go to Mesh Control ->
Row Mesh Control -> Optimization Control to adapt the mesh optimization parameters if necessary to enhance the quality of the mesh
Optimization is performed in the form of smoothing and is executed on each layer using multi-block elliptic techniques. The number of Optimization Steps represents the number of iterations performed with the elliptic smoother. By default, 100 iterations are applied.
5-14
57. Keep
default Optimization Steps and all other data identical
58. Close
the dialog box
Tutorials
Mesh Generation
5-2.6
Cascade Configuration
3D Mesh Generation
59. Click-left 60. Click
on Select All Rows
on the icon Generate 3D and confirm the generation
Once 3D grid generation is completed, grid quality is performed and displayed. Minimum cells skewness, the maximum expansion ratio and aspect ratio are reported, among others. Data are available for the entire mesh separately for every entity (row, technological effect, bulb). Data related to grid quality report are automatically stored in a report file, once the project file is saved. 61. Close
5-2.7
the dialog box. This page can also be reopened by clicking on
3D Mesh Visualization
62. Click-left 63. Select
on Select All Rows
View/toggle 3D Solid View to access the shaded blades in 3D view
64. Click-left
in 3D view; the Quick Access Pad (QAP) is modified
65. Click-right 66.
Tutorials
to get the contextual menu and activate Full View
Use View menu in QAP or View/Patch Viewer... menu to toggle edge or mesh
5-15
Cascade Configuration
5-2.8
Mesh Generation
Check Boundary Conditions & Mesh Quality
67. Check
for boundary conditions by clicking on
68. Select
UND under Type pull-down menu and check that no patches are in the patch list still set with an undefined type
5-16
Tutorials
Mesh Generation
Cascade Configuration
It is important to make sure that no undefined patches (UND) are present in the mesh. In that case, these can usually be removed by increasing the tolerance and launching the Search procedure. 69. Close
the dialog box
70. Check
for negative cells by clicking on
71. Click
on Apply The computation of the negative volumes is performed first. Negative cells can be outlined in the mesh pushing View neg cells button. Beware that the visualization of negative cells can be memory consuming when a large number of cells must be displayed. It is then advised to first check the number of negative cells by pressing the Apply button. It is mandatory to remove all negative cells before the calculation can be started.
72. Close
the dialog box
73. Check
for grid quality by clicking on
Detailed analysis of mesh quality on 3D mesh (in blocks, at boundaries and at FNMB) can be performed only once the 3D mesh has been generated. Information on orthogonality, angular deviation, aspect ratio, expansion ratio and cell width can be outlined in this window using the Type pull-down menu.
Click Left
Tutorials
5-17
Cascade Configuration
74. Select
Mesh Generation
quality criteria using the Type pull-down menu
75. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn per block (0 = all blocks)
76. Click-left
on part of the histogram to plot the concerned cells in the 3D view
77. Click-left on
More info button to obtain information about minimum and maximum values of the selected criteria
78. Close
5-2.9 79.
the dialog box
Save Project Go to File -> Save Project As to save mesh and template files The mesh files (7 files) contain the multiblock mesh topology, geometry and grid points and the boundary condition types: ".bcs", ".cgns", ".geom" (".xmt_txt"), ".igg", ".config" and ".qualityReport".The meaning of these files is detailed in the user manual. The template files (4 files) contain the parameters and the geometry needed to reproduced the mesh with AutoGrid™: ".geomTurbo" (".geomTurbo.xmt_txt"), ".trb" and ".info". The meaning of these files is detailed in the user manual.
5-18
Tutorials
TUTORIAL 6:
Fin on Fan
6-1
Introduction
6-1.1
Introduction
The resolution of computational fluid dynamics (CFD) problems involves three main steps:
• spatial discretization of the flow equations • flow computation • visualization of the results To answer these questions, NUMECA has developed a Flow INtegrated Environment for internal and Turbomachinery assimilations. Called FINE™/Turbo, the environment integrates the following tools:
• IGG™ is an Interactive Geometry modeler and Grid generator software, based on structured multi-block techniques
• AutoGrid™ is a three-dimensional Automated Grid generation software, dedicated to turbomachinery applications. Similarly to IGG™, it is based on structured multi-block techniques
• Euranus is a state-of-the-art multi-block flow solver, able to simulate Euler and Navier-Stokes equations in the laminar, transitional and turbulent regimes
• CFView™ is a highly interactive flow visualization and post-treatment software • FINE™ Graphical User Interface is a user-friendly environment that includes the different softwares. It integrates the concept of projects and allows the user to achieve complete simulations, going from the grid generation to the flow visualization, without the need of file manipulation A turbomachine is a device in which the energy is transferred either to or from a continuously flowing fluid by the dynamic action of one or more moving blade rows. It plays a major role in particular in aircraft, marine space (liquid rockets), land propulsion system but also in hydraulic, gas and steam turbines applications. It is also involved in industrial pipeline and processing equipment such as gas, petroleum and water pumping plants. Other applications can be related to heart-assist pumps, industrial compressors and refrigeration plants, among others. The turbomachinery field includes turbines, pumps, fans, compressors. A turbomachine is composed of several basic elements including the blade (also called vane if it is non-rotating), hub, and shroud. Several technological effects involving clearances, seal leakages and cooling holes among
Tutorials
6-1
Fin on Fan
Introduction
others can complete the machine. Due to the complexity of the blade shapes, the presence of technological elements and the rotation of machine, the nature of the flow is strongly three-dimensional, often depicting complex flow paths. This tutorial is particularly adapted to the mesh generation of a fin on fan in bypass turbomachine applications. It makes exclusive use of AutoGrid™ v8 and describes the main actions required to mesh the configuration of interest. In this tutorial you will learn how to:
• • • •
Define geometry into AutoGrid™ v8; Control meridional flow paths especially at the fin and nozzle; Control the blade-to-blade mesh; Control the quality of the mesh in the blade-to-blade and 3D mesh.
6-1.2
Prerequisites
This tutorial does not require any particular prerequisite but it is strongly recommended for beginners to perform the basic tutorials 1 to 7 and the advanced tutorial 3.
6-1.3
Problem Description
The problem to be considered is shown schematically here below (meridional view). The project consists in the mesh generation of a bypass configuration with a fan including a fin.
Fin
6-1.4
Preparation
• Copy the files located in cdrom:\DOC\_Tutorials\AutoGrid\_advanced\Tutorial_6 to your working directory, where cdrom must be replaced by the name of your DVD-ROM.
• Start AutoGrid™ v8.x For LINUX and UNIX systems, you can access AutoGrid™ v8.x graphical user interface with the following command line igg -niversion 8x -print or igg -niversion autogrid8x -print
6-2
Tutorials
Introduction
Fin on Fan
For WINDOWS systems, you can access AutoGrid™ v8.x graphical user interface from the start menu going to /Programs/NUMECA software/fine8x/IGG or /Programs/NUMECA software/autogrid8x/IGG
4
• Access the menu Modules, select AutoGrid and confirm "yes" to enter AutoGrid™ v8. You’re now ready to start the grid generation process and mesh the bypass configuration with a fin on fan!
Tutorials
6-3
Fin on Fan
Mesh Generation
AutoGrid™ v8 graphical user interface includes several windows that allow to visualize the geometry and mesh of the turbomachine simultaneously in the meridional, blade-to-blade and 3D view. The access to main menu and controls is proposed through a menu bar and a quick access pad, and is completed with a tool/icon bar. The execution of the different actions undertaken is summarized in the message box at the bottom of the interface.
6-2
Mesh Generation
A step by step approach is proposed in the following lines. It aims at driving you through the various steps that need to be executed from the creation of the mesh project to the validation of the final mesh quality.
6-2.1 1.
Create Mesh Project Close the Open Turbo Project Wizard dialog box The Open Turbo Project Wizard dialog box enables the user to retrieve a ".trb" file (with associated grid) including the data required to regenerate a mesh on an identical or similar geometry. In this tutorial, these data will be progressively introduced based on the geometry of the project case.
2.
Go to menu File -> New Project
3.
Click yes to close the active project
4.
Activate With ByPass and With Fin on Fan options The Fin on Fan option is only allowed for Bypass configuration.
5.
6-2.2
Choose the icon Start a New Project From Scratch
Load Geometry & Define Main Properties
6.
Click-left row1 in Rows Definition the current row
7.
Click-left in the meridional view
8.
Go to Geometry Definition
row 1 in the Quick Access Pad (QAP) to activate
Import and Link CAD
Graphic window opens, allowing geometry import.
6-4
Tutorials
Mesh Generation
9.
Fin on Fan
Click-left on File
10. Select 11.
• • • •
Open...
geometry.dat file from the file chooser
Define the geometry orientation if necessary Select Geometry Axis... in the Edit menu Adapt origin, stream direction if required - keep default Apply Close dialog box
12. Define
the hub curve
• Click-left on the curve defining the hub as it turns to yellow • Click-right and select Link to Hub Hub curve is displayed in the meridional view.
13. Define
the shroud curve
• Click-left on the curve defining the shroud as it turns to yellow • Click-right and select Link to Shroud Shroud curve is displayed in the meridional view.
Tutorials
6-5
Fin on Fan
Mesh Generation
14. Define
the nozzle curve
• Click-left on the curve defining the nozzle as it turns to yellow • Click-right and select Link to Nozzle Nozzle curve is displayed in the meridional view.
15. Define
the blade
• Click-left row1 in Rows Definition
row 1 in the Quick Access Pad (QAP) to activate
the current row, if not done already
• Click-left on first surface defining the blade when highlighted in blue (it turns to red or yellow)
• Click-middle to select the second surface defining the blade • - click-left on second surface defining the blade when highlighted in blue (it turns to red or yellow)
Click Left
Click Middle Click Left
The View/View Solid menu acts as a toggle and allows to visualize the surfaces that are active.
6-6
Tutorials
Mesh Generation
Fin on Fan
• Click-right and select Link to Blade Blade is displayed in the meridional view.
16. Define
leading edge and trailing edge
• Click-left row1 in Rows Definition
row 1 in the Quick Access Pad (QAP) to activate
the current row, if not done already
• • • •
Click-left at blade leading edge line definition, inside the Import CAD window As it turns yellow, click-right and select Link to Leading Edge Click-left at blade trailing edge line definition, inside the Import CAD window As it turns yellow, click-right and select Link to Trailing Edge Leading and trailing edges are displayed in the meridional view.
17. Define
fin on fan
The fin has to be defined by two curves defining respectively the upper and down sides of the axisymmetric fin.
• Click-left row1 in Rows Definition
row 1 in the Quick Access Pad (QAP) to activate
the current row, if not done already
• • • •
Tutorials
Click-left at upper side curve of the fin, inside the Import CAD window As it turns yellow, click-right and select Link to Fin Up Click-left at lower side curve of the fin, inside the Import CAD window As it turns yellow, click-right and select Link to Fin Down
6-7
Fin on Fan
Mesh Generation
When blade intersect hub and shroud, inlet and outlet are displayed in the meridional view. Control lines are automatically appearing for the control of the flow paths around the fin and the bypass nozzle.
18. Go
to File -> Exit The geometry of the fin can also be defined from a native ".geomTurbo" file. The ".geomTurbo" file format is structured in three main blocks: the header, the channel and the row(s) definitions. The header when defining a bypass configuration should contain the keywords "byPass yes".
The channel format contains the definition of the turbomachinery meridional contour (hub and shroud). It is composed by curves defined by a set of points. The ".geomTurbo" file must contain two channel curves named respectively "hub" and "shroud". The row definition contains the geometry of the fin and the complete row. The fin is defined by two curves: upper_curve and lower_curve defining the axisymmetric surfaces that will be used to define the fin. The blade is defined by the pressure and the suction side surfaces identified by the keywords "pres-
6-8
Tutorials
Mesh Generation
Fin on Fan
sure" and "suction". Both surfaces are specified by a set of cross sections of the blade at several spanwise location from hub to shroud. Each section is defined by a set of points from leading to trailing edge.
19. Click-left
on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active it
20. Click-right
Tutorials
on row 1 and select Properties in the pop-up menu
21. Enter
the Periodicity (number of blades) to
22. Keep
in Rotation Speed (rpm)
6-9
Fin on Fan
Mesh Generation
The speed will be transferred to FINE™ graphical user interface and ease the input of boundary conditions later on. The sign of the rotational speed is positive (+) when the blade row is rotating in the positive θ direction, and negative otherwise 23. Select
Rotor as a row type and Axial as a row orientation
The row type and row orientation settings are only information that will not impact or control the mesh generation process. 24. Activate
Default in order to plot the full turbomachine in 3D view when selecting View/ toggle 3D Solid View
25. Close
the dialog box
26. Click-left
on Rows Definition -> row 1
27. Click-right
and select Define Shroud Gap in the pop-up menu
28. Set
Width At Leading Edge = [Meters]
29. Set
Width At Trailing Edge = [Meters]
The width at leading/trailing edge allows to specify the size of the gap respectively at the leading and trailing edge of the blade. The gap curve is then constructed as a linear offset of the hub (or the shroud) according to these values. 30. Click-left
6-10
on Select All Rows
31. Select
toggle 3D Solid View in the View menu to access the shaded blades in 3D view
32. Select
toggle 3D Solid View in the View menu to remove the shaded blades in 3D view
Tutorials
Mesh Generation
6-2.3
Fin on Fan
Set Default Topology
33. Click-left 34. Select
on Select All Rows
Grid Level/Medium through Mesh Control in Quick Access Pad
35. Estimate
the width of the first cell at the wall:
The width of the first cell close to the wall must be selected with care since the quality of the flow solution will often depend upon the capture of the flow phenomena inside the boundary layers which develop along the solid walls. Depending upon the turbulence model selected, NUMECA recommends to locate the nearest grid point along the wall, at a distance that corresponds to parietal coordinate y+ ranging from 1-5 (low Reynolds number models) or 3050 (high Reynolds number models). Assuming thermal effects must be modelled accurately, y+ can reach values as low as 0.1. The relation between the parietal coordinate y+ and width of the first cell close to the wall y is driven by the Blasius equation, expressed as follows for turbulent flows:
where: - ywall is the distance of the nearest grid point to the wall (in meter); - Vref is a reference velocity of the flow, for instance the inlet velocity (in m/s); - υ is the kinematic viscosity of the fluid (in m2/s), i.e. the dynamic viscosity divided by the density; - Lref is a reference length of the test case (in meter); - y+ is a non-dimensional value. Input the value of the Cell Width = [Meters] in Row Mesh Control.
Tutorials
6-11
Fin on Fan
Mesh Generation
36. Select
(Re)set Default Topology in the toolbar and confirm (yes). This button will set the mesh topology to the default skin-like topology
37. Click-left
on yes to perform an automatic switch to matching topology that is required because of the control lines used to define the fin that are on the blade (row 1)
6-2.4
Meridional Control When overlapping detected in the flow paths, a warning is appearing at the bottom of the graphical user interface. In addition, the expansion ratio is plotted in the message box.
38. Control
bypass - nozzle - fin points distributions
• Click-left on Select All Rows • Click-left on Mesh Control -> Row Mesh Control -> Flow Paths Control -> Expert • Deactivate View Flow Path to plot the grid used to generate the flow paths • Close dialog box
6-12
Tutorials
Mesh Generation
Fin on Fan
• Click-left on • Click-left on number of flow paths down the nozzle, decrease to to add more flow paths between the nozzle and the fin
• Click-left on Select All Rows • Click-left on Generate Flow Paths
Click Left
More information about the control of the nozzle and bypass points distribution are provided in advanced tutorial 3.
• • • •
Click-left on control line defining the nozzle topology when highlighted in yellow Click-left on control point defining the control line Move control point at desired location Click-left on control point to validate its new location
Click Left Click Left
The exact coordinates of the control points can also be introduced with clickright on the control point; a dialog box appears, enabling the user to enter the point coordinates in (rz) mode.
Tutorials
6-13
Fin on Fan
Mesh Generation
• Click-left on Select All Rows • Click-left on Generate Flow Paths
39. Check
quality of the flow paths
• Click-left in meridional view to activate it (red border) • Click-left on • Select quality criteria using the Type pull-down menu • Click-left on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn for each row
• Click-left on part of the histogram to plot the concerned cells in the meridional view • Click-left on More info button to obtain information about minimum and maximum values of the selected criteria
• Close dialog box
Click Left
6-2.5
Blade-to-Blade Control
40. Click 41. Go
on Generate B2B
to Mesh Control
6-14
Row Mesh Control
B2B Mesh Topology Control
Topology
Tutorials
Mesh Generation
Fin on Fan
By default, matching connections are applied at periodic boundaries because of the control lines used to control the flow paths along the fin that are on the blade (row 1). You can see the periodic boundary by showing the repetitions. 42. Click-left 43. Go
on the blade-to-blade window to activate that view (red border)
to the menu View-> Repetition
44. Increase
Nb Repet to and Show
45. Close
the dialog box
46. Keep
Matching Periodicity activated and all other data identical In several turbomachinery types, the blades are highly staggered (Automatic High Staggered Blade Detection within AutoGrid™). If the solid angle at the inlet (outlet) of the machine becomes greater than 450 and if the location of the inlet (outlet) limits of the domain is close to the leading edge (trailing edge) of the blades, then the default topology is not suitable anymore since the cells located near the inlet (outlet) boundary become very skewed. To improve this unexpected behaviour, AutoGrid™ uses the High Staggered Blade Optimization.
47. Deactivate
Topology option
48. Go
to Mesh Control Row Mesh Control B2B Mesh Topology Control -> Grid Points to control the number of grid points in the blade-to-blade view if necessary Click-left on the number of nodes, make the proper modification in the entry box and press to confirm the modification. The number of points
Tutorials
6-15
Fin on Fan
Mesh Generation
specified is recommended to be 4xn + 1 (where n is an integer) to allow multigrid process on minimum 3 grid levels within FINE™. Visualize the result in blade-to-blade view after selecting Generate B2B to regenerate the flow paths and the mesh in blade-to-blade plane. 49. Keep
default points distribution
50. Deactivate 51. Close
Grid Points option
the dialog box
to Mesh Control -> Active B2B Layer to specify the flow path (layer) on which the blade-to-blade mesh will be plotted in the blade-to-blade view
52. Go
By default, the active layer is the hub of the machine (Active Layer (%span) set to 0). The layer selected for visualization is defined in percentage of span, going from hub (0%) to shroud (100%) and is applied on active row(s). 53. Click-left 54. Enter
on Select All Rows
for example in order to visualize the mesh at 50% span
55. Select
Generate B2B to regenerate the blade-to-blade mesh on new specified layer in the blade-to-blade view Detailed analysis of mesh quality can be performed on Blade-to-Blade mesh after generation. Information on orthogonality, aspect ratio and expansion ratio can be outlined in this window using the Type pull-down menu and plotted in the blade-to-blade view on active layer selected in Mesh Control/ Active B2B Layer.
56. Check
for grid quality by clicking on
57. Select
quality criteria using the Type pull-down menu
58. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn for each row
59. Click-left
on part of the histogram to plot the concerned cells in the blade-to-blade view
60. Click-left on
More info button to obtain information about minimum and maximum values of the selected criteria
Click Left
6-16
Tutorials
Mesh Generation
Fin on Fan
61. Close
the dialog box
62. Go to Mesh Control ->
Row Mesh Control -> Optimization Control to adapt the mesh optimization parameters if necessary to enhance the quality of the mesh
Optimization is performed in the form of smoothing and is executed on each layer using multi-block elliptic techniques. The number of Optimization Steps represents the number of iterations performed with the elliptic smoother. By default, 100 iterations are applied. 63. Keep
default Optimization Steps and all other data identical
64. Close
the dialog box
6-2.6
3D Mesh Generation
65. Click-left 66. Click
67. If
on Select All Rows
on the icon Generate 3D and confirm the generation
at the end of the generation, a warning as presented below appears, click-left on Ok
This warning prevents the user that when checking the grid quality (angular deviation along J) if a discontinuity is detected, the user has to reduce the expansion ratio in the Mesh area of the B2B Mesh Topology Control dialog box. In addition, the blade-to-blade mesh can be plotted on the concerned active layer (i.e. layer 132) by repeating the steps 52 to 55.
Tutorials
6-17
Fin on Fan
Mesh Generation
Once 3D grid generation is completed, grid quality is performed and displayed. Minimum cells skewness, the maximum expansion ratio and aspect ratio are reported, among others. Data are available for the entire mesh separately for every entity (row, technological effect, bulb). Data related to grid quality report are automatically stored in a report file, once the project file is saved.
68. Close
6-2.7
the dialog box. This page can also be reopened by clicking on
3D Mesh Visualization
69. Click-left 70. Select
on Select All Rows
View/toggle 3D Solid View to access the shaded blades in 3D view
71. Click-left
in 3D view; the Quick Access Pad (QAP) is modified
72. Click-right 73.
6-18
to get the contextual menu and activate Full View
Use View menu in QAP or View/Patch Viewer... menu to toggle edge or mesh
Tutorials
Mesh Generation
6-2.8
Fin on Fan
Check Boundary Conditions & Mesh Quality
74. Check
for boundary conditions by clicking on
75. Select
UND under Type pull-down menu and check that no patches are in the patch list still set with an undefined type
It is important to make sure that no undefined patches (UND) are present in the mesh. In that case, these can usually be removed by increasing the tolerance and launching the Search procedure. 76. Close
the dialog box
77. Check
for negative cells by clicking on
78. Click
on Apply The computation of the negative volumes is performed first. Negative cells can be outlined in the mesh pushing View neg cells button. Beware that the visualization of negative cells can be memory consuming when a large number of cells must be displayed. It is then advised to first check the number of negative cells by pressing the Apply button.
Tutorials
6-19
Fin on Fan
Mesh Generation
It is mandatory to remove all negative cells before the calculation can be started.
79. Close
the dialog box
80. Check
for grid quality by clicking on
Detailed analysis of mesh quality on 3D mesh (in blocks, at boundaries and at FNMB) can be performed only once the 3D mesh has been generated. Information on orthogonality, angular deviation, aspect ratio, expansion ratio and cell width can be outlined in this window using the Type pull-down menu. 81. Select
quality criteria using the Type pull-down menu
82. Click-left
on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn per block (0 = all blocks)
83. Click-left
on part of the histogram to plot the concerned cells in the 3D view
Click Left
84. Click-left on
More info button to obtain information about minimum and maximum values of the selected criteria
6-20
Tutorials
Mesh Generation
Fin on Fan
85. Close
6-2.9 86.
the dialog box
Save Project Go to File -> Save Project As to save mesh and template files The mesh files (7 files) contain the multiblock mesh topology, geometry and grid points and the boundary condition types: ".bcs", ".cgns", ".geom" (".xmt_txt"), ".igg", ".config" and ".qualityReport".The meaning of these files is detailed in the user manual. The template files (4 files) contain the parameters and the geometry needed to reproduced the mesh with AutoGrid™: ".geomTurbo" (".geomTurbo.xmt_txt"), ".trb" and ".info". The meaning of these files is detailed in the user manual.
Tutorials
6-21
Fin on Fan
6-22
Mesh Generation
Tutorials
TUTORIAL 7:
3D Technological Effect Casing Treatment
7-1
Introduction
7-1.1
Introduction
The resolution of computational fluid dynamics (CFD) problems involves three main steps:
• spatial discretization of the flow equations • flow computation • visualization of the results To answer these questions, NUMECA has developed a Flow INtegrated Environment for internal and Turbomachinery assimilations. Called FINE™/Turbo, the environment integrates the following tools:
• IGG™ is an Interactive Geometry modeler and Grid generator software, based on structured multi-block techniques
• AutoGrid™ is a three-dimensional Automated Grid generation software, dedicated to turbomachinery applications. Similarly to IGG™, it is based on structured multi-block techniques
• Euranus is a state-of-the-art multi-block flow solver, able to simulate Euler and Navier-Stokes equations in the laminar, transitional and turbulent regimes
• CFView™ is a highly interactive flow visualization and post-treatment software • FINE™ Graphical User Interface is a user-friendly environment that includes the different softwares. It integrates the concept of projects and allows the user to achieve complete simulations, going from the grid generation to the flow visualization, without the need of file manipulation A turbomachine is a device in which the energy is transferred either to or from a continuously flowing fluid by the dynamic action of one or more moving blade rows. It plays a major role in particular in aircraft, marine space (liquid rockets), land propulsion system but also in hydraulic, gas and steam turbines applications. It is also involved in industrial pipeline and processing equipment such as gas, petroleum and water pumping plants. Other applications can be related to heart-assist pumps, industrial compressors and refrigeration plants, among others. The turbomachinery field includes turbines, pumps, fans, compressors. A turbomachine is composed of several basic elements including the blade (also called vane if it is non-rotating), hub, and shroud. Several technological effects involving clearances, seal leakages and cooling holes among
Tutorials
7-1
3D Technological Effect Casing Treatment
Introduction
others can complete the machine. Due to the complexity of the blade shapes, the presence of technological elements and the rotation of machine, the nature of the flow is strongly three-dimensional, often depicting complex flow paths. This tutorial is particularly adapted to the mesh generation of casing treatments (3D technological effects) for turbomachines. It makes exclusive use of AutoGrid™ v8 and describes the main actions required to mesh the configuration of interest. In this tutorial you will learn how to:
• • • •
7-1.2
Read an existing project file into AutoGrid™ v8; Adapt the existing project file; Generate and control the mesh in the technological effect (casing); Control the quality of the mesh in the 3D mesh.
Prerequisites
This tutorial does require to perform the mesh generation of the NASA rotor 37 explained in basic tutorial 1. Furthermore, it is strongly recommended for beginners to perform the basic tutorials 2 to 7 too.
7-1.3
Problem Description
The problem to be considered is shown schematically here below. The project consists in the mesh generation of a casing treatment (3D technological effect) for the NASA rotor 37. 0.0356 0.02
Rotor-Stator
AutoGrid Mesh
7-1.4
3d techno effect
Preparation
• Copy the files located in cdrom:\DOC\_Tutorials\AutoGrid\_advanced\Tutorial_7 to your working directory, where cdrom must be replaced by the name of your DVD-ROM.
• Start AutoGrid™ v8.x
7-2
Tutorials
Introduction
3D Technological Effect Casing Treatment
For LINUX and UNIX systems, you can access AutoGrid™ v8.x graphical user interface with the following command line igg -niversion 8x -print or igg -niversion autogrid8x -print For WINDOWS systems, you can access AutoGrid™ v8.x graphical user interface from the start menu going to /Programs/NUMECA software/fine8x/IGG or /Programs/NUMECA software/autogrid8x/IGG
4
• Access the menu Modules, select AutoGrid and confirm "yes" to enter AutoGrid™ v8. You’re now ready to start the grid generation process and mesh the configuration presenting a casing treatment (3D technological effect)!
Tutorials
7-3
3D Technological Effect Casing Treatment
Mesh Generation
AutoGrid™ v8 graphical user interface includes several windows that allow to visualize the geometry and mesh of the turbomachine simultaneously in the meridional, blade-to-blade and 3D view. The access to main menu and controls is proposed through a menu bar and a quick access pad, and is completed with a tool/icon bar. The execution of the different actions undertaken is summarized in the message box at the bottom of the interface.
7-2
Mesh Generation
A step by step approach is proposed in the following lines. It aims at driving you through the various steps that need to be executed from the creation of the mesh project to the validation of the final mesh quality.
7-2.1
Open Existing Mesh Project
1.
Click on Select a Project File in the Open Turbo Project Wizard dialog box
2.
Select the file NASA-Rotor-37.trb
3.
Click Open to load the selected project
The Open Turbo Project Wizard dialog box enables the user to retrieve a ".trb" file (with associated grid) including the data required to regenerate a mesh on an identical or similar geometry. In this tutorial, these data will be progressively introduced based on the geometry of the project case.
7-2.2
Adapt Mesh Project
4.
Click-left row1 in Rows Definition the current row
5.
Click-left in the meridional view
6.
Go to Geometry Definition
row 1 in the Quick Access Pad (QAP) to activate
Import and Link CAD
Graphic window opens, allowing geometry import.
7-4
Tutorials
Mesh Generation
3D Technological Effect Casing Treatment
7.
Click-left on File
Open...
8.
Select geometry.dat file from the file chooser
9.
Define the new shroud curve
• Click-left on the curve (new_shroud) as it turns to yellow • Click-right and select Link to Shroud New shroud curve is displayed in the meridional view.
New Shroud
10. Go 11.
to File -> Exit
Click-left on the " + " before row1 in QAP to get the blade information
12. Click-left on
Blades the contextual menu
Main Blade
Shroud gap, click-right and select Properties in
13. Set
Width At Leading/Trailing Edge to to define the main blade tip in addition of the 3D technological effect thickness (0.0356 - 0.02)
Tutorials
14. Keep
all other data identical
15. Close
the dialog box
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3D Technological Effect Casing Treatment
16. Control
Mesh Generation
flow paths through Mesh Control -> Row Mesh Control -> Flow Paths Con-
trol 17. Set
Cell width at Shroud to
18. Keep
all other data identical
19. Click
on Generate to regenerate flow paths
20. Close
the dialog box
21. Click
on Generate B2B (active layer = 0%)
to generate blade-to-blade mesh by default on hub
on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active the current row, if not done already
22. Click-left 23. Click
7-6
on the icon Generate 3D and confirm (Start) the generation
Tutorials
Mesh Generation
3D Technological Effect Casing Treatment
Once 3D grid generation is completed, grid quality is performed and displayed. Minimum cells skewness, maximum expansion ratio and aspect ratio are reported, among others. Data are available for the entire mesh separately for every entity (row, technological effect, bulb). Data related to grid quality report are automatically stored in a report file, once the project file is saved.
24. Close
7-2.3
the dialog box
3D Technological Effect Generation
7-2.3.1 Configuration Control on Rows Definition -> row 1 in the Quick Access Pad (QAP) to active the current row, if not done already
25. Click-left 26. Click
Tutorials
on the button Add 3D Effect to add a 3D technological effect in the configuration
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3D Technological Effect Casing Treatment
Mesh Generation
7-2.3.2 Geometry Definition on Rows Definition -> row 1 -> 3d techno effect 1 in the Quick Access Pad (QAP) if not active already
27. Click-left 28. Go
to Geometry Definition
Import and Link CAD
Graphic window opens, allowing geometry import. 29. Select
the curves and surfaces defining the active 3D technological effect
• -click-left on all the curve(s) (from curve_1 to curve_8) as they turn to yellow • -click-left on all the surface(s) (from surface_1 to surface_3) as they turn to blue • Click-right and select Link to 3D Effect
30. Go
to File -> Exit
on Rows Definition -> row 1 -> 3d techno effect 1 in the Quick Access Pad (QAP) if not active already
31. Click-left
32. Click-right
on 3d techno effect 1 to get the contextual menu and select Edit to access the 3D technological effect edition mode
Curves and surfaces defining the selected 3d technological effect are displayed in the 3D view.
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Tutorials
Mesh Generation
3D Technological Effect Casing Treatment
Curves and surfaces defining the 3d technological effects are specified in the ".geomTurbo" file (see User Manual for more details). In the edition mode, it is not recommended to define new geometrical entities by using the Geometry menu. Otherwise, when relaunching the template including the 3d technological effect, problems may occur (see User Manual for more details).
7-2.3.3 Topology & Mesh Control The domain defining a technological effect must be filled by several structured 3D blocks (like in IGG™). The block edges are mapped on the geometry. The Grid subpad provides the tools to create and control the blocks 33. Click-left
on Insert New Face icon in the Grid subpad to start to fill the geometry
34. Click-left
to locate the first corner of the 2D block (yellow spot when attracted on existing
curve) 35. Click-left
to locate the opposite corner of the 2D block
36. Click-left
to create the 2D block
37. Click-left
on vertex (when highlighted in yellow) of the 2D block to move it when neces-
sary 38. Click-left 39. Repeat
Tutorials
to fix the new position of the vertex on the geometry
steps 37 and 38 for all vertices defining the 2D block
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3D Technological Effect Casing Treatment
Mesh Generation
40. Repeat
steps 33 to 39 in order to fill the "inlet" geometry of the technological effect with two new faces as presented in the figure below
41. Change
• • • •
the number of points on edges:
Click-left on edge (highlighted in yellow) Click-right and select Segment/Set Number of Points Set number of points (by default set to 9) as presented in figure below Apply
13
25
25 9
9 13
The number of points specified is recommended to be 4xn + 1 (where n is an integer) to allow multigrid process on minimum 3 grid levels within FINE™. 42. Change
the points distribution on edges defining two groups:
• Click-left on one edge (highlighted in yellow)
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Tutorials
Mesh Generation
3D Technological Effect Casing Treatment
• Click-right and select Segment/Distribution: a new window appears
• • • • •
Click-left on Define/Edit Group Click-left on Create Set a userdefined group name - to validate Click-left to select edges to include in group-1 Click-middle to add the selected edge in the group-1 as presented in figure below
If the menu to select and/or add edges in a group is no more available, clickleft on the group in the list and click-left on Modify.
• Click-left on Create • Set a userdefined group name - to validate • Click-left to select edges to include in group-2
Tutorials
7-11
3D Technological Effect Casing Treatment
Mesh Generation
• Click-middle to add the selected edge in the group-2 as presented in figure below
• • • •
Close the dialog box Select group-1 under Group name Impose Hyperbolic Tangent with a cell width of at start and end Click-left on Apply to group
• Select group-2 under Group name • Impose Hyperbolic Tangent with a cell width of at start and at end • Click-left on Apply to group
43. Close
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the dialog box
Tutorials
Mesh Generation
3D Technological Effect Casing Treatment
44. Create
the 3D blocks starting from the 2D grid faces:
• Click-left on edge to select grid face (highlighted in white or black) • Select Block by Face Translation • In keyboard input area, type to allow edge creations - to select translation - as translation vector - to avoid geometry creation - to avoid to intersect selected surfaces: a 3D block is created by translating the 2D grid face
• Repeat the above steps for the others two 2D grid faces
45. Connect
the 3D blocks together:
• Select Connect / Face-Face • Click-left on edge to select the reference face (highlighted in white or black) of the concerned block (highlighted in red)
• • • •
Tutorials
Click-middle to aknowledge Click-left on edge to select the second face to connect Click-middle to aknowledge: a new window appears Click-left on All: faces appear in green or red if well connected
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3D Technological Effect Casing Treatment
Mesh Generation
• Repeat the above steps for the others two faces to connect
• Close the dialog box connect_faces 46. Change
• • • •
the number of points in the axial direction:
Click-left on edge (highlighted in yellow) Click-right and select Segment/Set Number of Points Set number of points (by default set to 9) as presented in figure below Apply
47. Map
the 3D blocks on the imported curves:
• Click-left on vertex (when highlighted in yellow) of the 3D block to move it on curves • Click-left to fix the new position of the vertex on the geometry • Repeat above steps for all vertices defining the 3D blocks
Click-Left
Click-Left
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Tutorials
Mesh Generation
3D Technological Effect Casing Treatment
48. Generate
3D mesh by click-left on Block 6 Bnd and select blocks 8 to 10 - Apply
7-2.3.4 Boundary Conditions & Quality Control 49. Define
• • • • •
the periodicity of the blocks in the 3d technological effect:
Select Periodicity in the Grid menu Enter in Block area Select ROTATION Adapt Axis and Number Of Periodicity as presented below - to validate Apply
720
• Repeat above steps for block 9 and 10 • Close the dialog box 50. Adapt
and check boundary conditions:
• Select Boundary Conditions in the Grid menu • Click on Search to define automatically the connections between blocks 8, 9 and 10: 2 connections and 1 periodic connection are created
Tutorials
7-15
3D Technological Effect Casing Treatment
Mesh Generation
• Type under Name area • -left-click on the patches as presented in figure below • Click-left on button Set Patch Type and drag to ROT to change shroud type from solid (SOL) to rotor/stator (ROT)
Click-Left Click-Left
• Select UND under Type area • -left-click on the patches as presented in figure below • Click-left on button Set Patch Type and drag to ROT to change type from undefined (UND) to rotor/stator (ROT)
Click-Left
• -left-click on the patches as presented in figure below • Click-left on button Set Patch Type and drag to SOL to change type from undefined (UND) to solid (SOL)
Click-Left
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Tutorials
Mesh Generation
3D Technological Effect Casing Treatment
• Select UND under Type pull-down menu and check that no patches are in the patch list still set with an undefined type It is important to make sure that no undefined patches (UND) are present in the mesh. In that case, these can usually be removed by increasing the tolerance and launching the Search procedure.
• Close the dialog box 51. Check
for negative cells by clicking on
- Apply
The computation of the negative volumes is performed first. Negative cells can be outlined in the mesh pushing View neg cells button. Beware that the visualization of negative cells can be memory consuming when a large number of cells must be displayed. It is then advised to first check the number of negative cells by pressing the Apply button. It is mandatory to remove all negative cells before the calculation can be started. 52. Check
for grid quality by clicking on
Detailed analysis of mesh quality on 3D mesh (in blocks, at boundaries and at FNMB) can be performed only once the 3D mesh has been generated. Information on orthogonality, angular deviation, aspect ratio, expansion ratio and cell width can be outlined in this window using the Type pull-down menu.
• Select quality criteria using the Type pull-down menu • Click-left on Show chart to visualize the distribution of selected criteria in the form of an histogram. The histogram is drawn per block (0 = all blocks)
• Click-left on part of the histogram to plot the concerned cells in the 3D view • Click-left on More info button to obtain information about minimum and maximum values of the selected criteria
• Close the dialog box 53. Click
on Close Edition Mode All the actions performed during an editing session are stored in the template file (".trb") and can be replayed on similar geometries.
7-2.4 54.
Tutorials
Save Project Go to File -> Save Project As to save mesh and template files
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3D Technological Effect Casing Treatment
Mesh Generation
The mesh files (7 files) contain the multiblock mesh topology, geometry and grid points and the boundary condition types: ".bcs", ".cgns", ".geom" (".xmt_txt"), ".igg", ".config" and ".qualityReport".The meaning of these files is detailed in the user manual. The template files (4 files) contain the parameters and the geometry needed to reproduced the mesh with AutoGrid™: ".geomTurbo" (".geomTurbo.xmt_txt"), ".trb" and ".info". The meaning of these files is detailed in the user manual.
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Tutorials
