fluent gambit

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Creating Geometry in GAMBIT

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

Preliminaries-1 



Lowest order entity

Highest order entity

Objective: 

Create and mesh the fluid region for flow problems and solid regions for heat transfer (and structural analysis for Fidap Users).



Typically accomplished by constructing and working with lower order entity objects and volume primitives.

Terminology: 

Vertex - a point



Edge - a curve that is defined by at least 1 vertex (in the case of 1 vertex, the edge forms a loop)

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Face - a surface (not necessarily planar) bounded by at least 1 edge (except for sphere and torus)

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Volume - a geometric solid (as in a solids model), also can be thought of as an "air tight" set of bounding faces.

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Preliminaries-2 

Color Identification 



Vertices and Edges are colored according to the highest order entity to which they are connected. The coloring scheme is:    



Vertex (white) Edge (yellow) Face (light blue) Volume (green)

Undo/Redo: 

10 levels of undo by default.  

 

Undoes geometry, meshing, and zoning commands. Description window provides command to be undone when mouse is passed over undo button.

Left click to execute visible button operation. Right click to access options.

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

General Operations: Coordinate System 

Coordinate system Cartesian, Cylindrical and Spherical systems 

Using Offset/Angle or Vertices for location/orientation

"Active" coordinate system is default in all forms Grid creation with "snapping" of vertices -Recommended for simple geometries only Creation of rulers

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General Operations: Move/Copy 

Move/Copy 

Operations: 

Translate: (inputs are Ds)



Rotate: Vector

(x,y,z) Angle 

Reflect:

Plane normal to vector 



Scale:

Vector

Options: 

Connected geometry can also be Moved



Mesh and/or Zone types can be copied linked or unlinked

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

General Operations: Vector Definition Form 

Vector Definition form 





is used in: 

Rotate and Reflect (in Move/Copy)



Sweep and Revolve (in Face/Volume Create)

Methods: 

Coordinate system axis



Two existing vertices



An existing Edge



Two points defined by coordinates



Screen View

Magnitude option allows size of vector to be defined.

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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General Operations: Align 

Align 

Align is an alternative to Move - translate (+rotate). 

It uses vertices on the start and final position to move the object



Method of increased alignment with the use of vertex-pairs



Connected geometry can be included

3 +

1 + + 2

1 + + 2

Translation 3 +

Rotation ++

Plane alignment + +

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

General Operations: Connect 

Connect (Real) 

Vertices, Edges and Faces can be connected

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The operation eliminates all duplicate entities and reconnects upper topology

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Only entities within the ACIS tolerance will be connected



Existing mesh will be preserved

Copy +Translate

One Face

Connect Edges Two Edges

One Edge

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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General Operations: Disconnect 

Disconnect (Real) 

Vertices, Edges and Faces can be disconnected



The operation recreates duplicate entities and reconnects upper topology



Several options exists

Disconnect

One Edge

Edge + Vertices

Two Edges

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General Operations: Delete 

Delete 

Select Lower Geometry (default)  



Deletes Faces Deletes Lower Geometry: Edges and Vertices

Deselect Lower Geometry  

Deletes Faces Does NOT delete Lower Geometry: Edges and Vertices

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

Example: Deleting Entities that belong to higher order Entities

Incorrect: Attempt to delete Face (of a Volume)

The selected face can NOT be deleted because it is connected to a volume.

Correct: Delete Volume (deselect Lower Geometry)

Volume is deleted. Faces, Edges and Vertices are not deleted. Any of the six faces can be deleted

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

General Operations: Misc. 

Summarize/Query/Total Summary of vertex coordinates,lower topology, mesh information, element/node labels, etc. Checks for valid ACIS geometry Query: useful to associate geometrical objects with object names Get total number of Entities



Modify Color/Label Modify entity colors Change entity label

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Geometry Creation 

ACIS - geometry engine ("kernel") 





Provides tools for “bottom-up” creation by: 

Vertex:

Add, Grid Snap, etc.

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Edge:

Line, Arc, Ellipse, Fillet, B-spline, etc.



Face:

Wire Frame, Sweep, Net, etc.



Volume:

Wire Frame, Sweep, Face Stitch, etc.

Provides tools for “top-down” creation by 

Face Primitives:

Rectangle, Circle, Ellipse



Volume Primitives:

Brick, Cylinder, Sphere, etc.



Volume/Face Booleans:

Unite, Subtract, Intersect



Volume/Face Decompose:

Split

Geometry creation typically involves use of all tools.

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

"Bottom Up": Vertex Creation-1 

Real Vertex creation By coordinates 

Cartesian, cylindrical and spherical coordinate systems



Also available in virtual geometry

On edge 

If the intention is to split the edge, the Edge-Split form should be used instead

On face 

Useful to create edges on surface for a virtual split

In volumes 

Not frequently used

At edge-edge intersections 

Vertex is not connected to either edge



Split edge with vertex for connectivity

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"Bottom Up": Vertex Creation-2 

Import point data, File



File format: 

ICEM Input npc nc x1 y1 z1 x2 y2 z2 : xn yn zn

Where:

n = npc* nc npc nc xi yi zi 

is the total number of points is the number of points per curve is the number of curves are real or integer vertex coordinates

Vertex Data 

Format is similar, curve information is not needed

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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"Bottom Up": Edge Creation-1 

Real Edge creation Straight line 

Multiple edges can be created by selecting multiple vertices.

Arc,

Circle



Face create counterparts available



Creation Methods 

Three vertices on the edge



Using Center and End-points



Using Radius and Start/End Angles (Arc Only)

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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"Bottom Up": Edge Creation-2 

Real Edge creation Elliptical Arc 

Created by three vertices

Major Vertex + On Edge Vertex

Start Angle

+ End Angle

Center Vertex

+

Conic Arc 

Created by three vertices Shoulder Vertex +

+ End Vertex +

Start Vertex

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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"Bottom Up": Edge Creation-3 

Real Edge creation Fillet Arc 

Creates a fillet out of a corner +

Edge 1

+ +

Radius

Edge 2

NURBS 

Third-order by default



Use tolerance for the approximate option

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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"Bottom Up": Edge Creation-4 

Real Edge creation Revolve Vertex 

Select one or more vertices to rotate



Specify Angle



Axis is defined using Vector Definition Panel



Input Height for Spiral creation

Project Edge on Surface 

Limited to single edge and face



Direction defined in Vector Definition Panel

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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"Bottom Up": Face Creation-1 

Real Face creation Wire Frame 

Creates real and virtual faces



All edges have to be connected into one loop



Number of edges and order of picking are not important



If all edges are co-planar — creation is always successful

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For non-coplanar edges: 

The number of edges has to be 3 or 4



Edges cannot have the same tangent at the connecting vertex

+

create real face by wire frame co-planar edges

real face

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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"Bottom Up": Face Creation-2 

Real Face creation Parallelogram 

defined by three vertices

Polygon 

Selection order is important.



5 or more vertices must be coplanar.

Vertex rows 

Tolerance input

Skin 

Topologically parallel edges



Edges have to be picked in order



Both ends of all edges can coincide

Net 

Topologically intersecting edges

+ +

+ +

++ +++ +++ + +++ +

+

+

++ +++ +++ + +++ +

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

"Bottom Up": Face Creation with Revolve 

Real Face creation Revolve (With or without mesh) 

Using an edge, an angle and a revolving vector



Use vectors for definition of the axis of revolution



Basic edge can coincide with axis

axis of revolution

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

"Bottom Up": Face Creation with Sweep 

Real Face Creation: Sweep (with or without mesh) 

Rigid sweep 



Perpendicular sweep: Draft and Twist option 



Edge translated along sweep path without being rotated Angle edge makes with sweep path is maintained as edge swept along path

Be careful not to create degenerate faces 

Sweep path start tangent vector parallel to edge tangent Rigid

Perpendicular Draft: Angle=0

Perpendicular Draft: Angle = - 30, 0, 30

Perpendicular Twist: Angle = 120

Rigid

Edge Path Edge

Path

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Face Primitives 

Face Primitives 

Dimensions and Plane/Direction must be specified Rectangles Circles Ellipses

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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"Bottom Up": Volume Creation-1 

Real Volume creation Stitch 

Create volumes out of connected faces 

If a few faces are missing, GAMBIT automatically finds the missing faces



Available in virtual geometry



Order of picking not essential



Voids not allowed

ten connected faces

Revolve (With or without mesh) 

Using a face, a revolving vector and an angle



Use edges or vectors for definition of  the axis of revolution

axis of

revolution

one volume

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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"Bottom Up": Volume Creation-2 

Real Volume creation Wire Frame 

Create volumes from connected curves



Number of edges and order of picking is not important



Voids and seamless volumes and faces cannot be created



Same limitation as face wire frame creation, for each face

36 connected edges

one volume

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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"Bottom Up": Volume Creation with Sweep 

Real Volume Creation: Sweep (with or without mesh) 

Rigid sweep 



Perpendicular sweep: Draft and Twist option 



Edge translated along sweep path without being rotated Angle edge makes with sweep path is maintained as edge swept along path

Be careful not to create degenerate volumes 

Sweep path start tangent vector perpendicular to a face normal Rigid

Path

Perpendicular Draft: Angle=0

Perpendicular Twist: Angle = 60

Face Face

Path

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Volume Primitives-1 

Real Volume Primitives Brick  

Width (X), Depth (Y) and Height (Z)



The Width (X) value is used for Y and Z if  no other input is given.



10 different preset positions (each octant plus center)

Cylinder and

Frustum

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Height and two cross-sectional radii (3rd radius for frustum)



The Radius 1 value is used for remaining radii if no other radius input is given.



9 different preset directions (three in each axis)

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Volume Primitives-2 

Real Volume Primitives Prism and

Pyramid



Corresponding to input of cylinder and frustum



Number of sides



9 different preset directions (three in each axis)

Sphere - only one radius Torus 

Major and cross-sectional radii



Three axis locations

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Boolean Operations: Unite 

Real Face/Volume Boolean Unites 

The order of picking is not important (except for labeling)



Retain - keeps copies of the entities Unite Faces 

All faces must be coplanar or have matching tangents. A

B

A+ B

Unite Volumes A B

A+ B

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Boolean Operations: Subtract 

Real Face/Volume Boolean Subtract 

The order of picking is important



Retain - keeps copies of entities Subtract Faces 

All faces have to be coplanar A

B

A- B Multiple entities can be entered in second list box.

B-A

Subtract Volumes A

A B

A- B

B

B-A

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Boolean Operations: Intersection 

Real Face/Volume Boolean Intersect 

The order of picking is not important (except for labeling)



Retain - keeps copies of entities.



All entities must intersect each other. Intersect Faces 

All faces have to be coplanar A

Intersect Volumes

B

A B

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

Geometry Splitting- Edges 

The Split Operation: Employs the intersection of two geometric entities to divide one or both objects into two or more pieces. 



Useful for decomposing complicated geometries into smaller, simpler ones.

Edge Split 

Split an edge into two or more edges



Resulting edges are, by default, connected.



Edges can be split with: 

Point - specify U Value between 0 and 1 where edge will be split. 

Use 0.5 to split edge in half.



Vertex - must already be created.



Edge 

Must already be created



Bi-directional option results in both edges being split at point(s) of intersection.

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Geometry Splitting- Faces 

"Target Object"

Real Face Boolean Split  

The order of picking is important Faces do not need to be coplanar example: coplanar face splits

Split A

"Tool"

with B Two Faces Split B with A Bidirectional split 

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

Three Faces

In general, for all splits (edges, faces, volumes): 





"Tool" entities are, by default, deleted after split is performed Retain option prevents “Tool” entities from being deleted. By default, resulting objects are connected .

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Geometry Splitting- Volumes Real Volume Boolean Split





"Target" Object

The order of picking is important 

Volume/Volume splits

A B

Split A with B

"Tool" two volumes

A B

Split B with A two volumes



Volume/Face splits

A B

Bidirectional Split three volumes

two volumes

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Split vs. Subtract 

The appropriate operation to use can depend upon final geometry required. 

Subtract 



Cut-away shows one volume results 

Cannot mesh core region



Flow/Heat Transfer in annular region only

Split 



Start with two disconnected cylinders

Two connected volumes result 

Cut-away shows that both annular and core regions can be meshed.



Flow/Heat Transfer possible in both regions

Subtract + Retain "Tool" (inner cylinder) 

Two disconnected volumes result, appears same as split



Duplicate faces appear at interface 

Non-conformal mesh can result



Useful for multiple reference frame problem (Fluent)

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

Fluent User Services Center www.fluentusers.com

Bidirectional Split vs. Unite 

The appropriate operation to use can depend upon the need to create additional surfaces for: 

defining boundary conditions



controlling meshing distribution

Unite 

BiDirectional Split

Unite 

One volume results



Cut-away shows no interior faces

Start with two disconnected cylinders 

Bidirectional split 

Three connected volumes result



Cut-away shows multiple interior faces which can be used to:





define internal boundaries



help control mesh distribution in volume

Total represented volume is the same

Introductory GAMBIT Notes GAMBIT v2.1 Jul 2003

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Boolean Characteristics: Imprinting 

Uniting Connected Volumes Results in Imprinting Volume.1

A

B

C

Unite A with B

A and C are connected cubes, B is a cylinder inside both

Volume.2: face contains an imprint of the cylinder