Fluent Official Dm-training 2005
Short Description
Download Fluent Official Dm-training 2005...
Description
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Mesh Model FLUENT v6.1
2-1
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Agenda 9:00 Overview of Dynamic Mesh (DM) 9:30 Global Controls 10:00 Dynamic Zones 10:30 Motion Specification 11:00 Step-by-Step Procedure 11:15 Tutorial 1 12:00 Lunch 1:00 Step-by-Step Procedure 1:30 Tutorial 2 2:30 Examples 3:00 Tips-and-Tricks and Technical Discussion Session 2-2
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Overview of DM
2-3
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Mesh Overview
New feature in FLUENT 6.1 z
A general purpose model targeted for moving boundary problems z z z z
Built-in, no additional fee IC engines Valves Fuel injectors HVAC modules and much much more…
Can also be used for steady-state parametric studies Compatible with all physical models and solver types in FLUENT 6.1 Compatible with any pre-processor Fully parallelized
2-4
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Mesh Motion Schemes
Fluent offers three mesh schemes z z z
Spring analogy Local remeshing Dynamic layering
Mesh motion may be applied to individual zones Different zones may use different schemes for mesh motion Connectivity between adjacent deforming zones may be nonconformal
2-5
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Spring Analogy
Interior nodes behave like a spring or sponge Connectivity remains unchanged Limited to relatively small deformation when used as a standalone meshing scheme Available for tri, tet, quad, hex and wedge mesh element types
2-6
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Local Remeshing
As user-specified skewness and size limits are exceeded, local nodes and cells are added or deleted As cells are added or deleted, connectivity changes Available only for tri and tet mesh elements
2-7
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Layering
Cells are added or deleted as the zone grows and shrinks As cells are added or deleted, connectivity changes Available for quad, hex and wedge mesh elements
2-8
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Combination of Approaches
Initial mesh needs proper decomposition Layering z z
Remeshing z
Valve travel region Lower cylinder region Upper cylinder region
Non-conformal interface between zones
2-9
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Combination of Approaches
2 - 10
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Motion Specification
Internal node positions are automatically calculated based on user specified boundary motion Mesh motion scheme in each zone is automatically chosen based on element type in that zone Prescribed mesh motion z z
Position or velocity versus time i.e. ‘profile’ text file UDF with expression for position or velocity
Flow dependant motion z z z z
Mesh motion is coupled with the flow solution through a UDF Can integrate forces (pressure, gravity and viscous etc) Six degree of freedom UDF provided UDF readily customized for desired mesh motion 2 - 11
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Mesh Preview
Mesh motion can be previewed without calculating flow variables z z
Allows user to quickly check mesh quality throughout the simulation cycle Applicable to any dynamic mesh simulation
2 - 12
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Global Controls
2 - 13
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Overview
Define > Dynamic Mesh > Parameters z
z
Methods
z
toggle spring analogy, layering, remeshing approaches GUI dynamically changes to reflect selected methods
Dynamic Mesh model enables generic functionality In-Cylinder option adds specific functionality
2 - 14
definition of RPM, starting crank angle, crank period, etc... option enables IC specific profile format for valve motion
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Overview
Smoothing (spring) parameters z z z z
‘stiffness’ boundary node relaxation convergence tolerance (max) number of iterations
Layering parameters z
Remeshing parameters z z
2 - 15
split/collapse factor min/max volume max skewness
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Smoothing Edges between any two mesh nodes are idealized as a network of interconnected springs. A set of linear equations are derived based on force balance at the nodes. The node positions at each time-step are solved iteratively. By default smoothing is applied on tet/tri mesh. To apply smoothing for all type of mesh use: (rpsetvar 'dynamesh/spring/all-element-type? #t) Spring Constant Factor: It adds “damping” to the springs [1,0] Boundary Node Relaxation: Under-relaxation used for the boundary nodes. Use a value of 0 if no smoothing on the boundaries
z
A default value of 1.0 is used for interior nodes
Convergence Tolerance: Used when solving for node positions. Number of Iterations: Max number of iterations. 2 - 16
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Smoothing
Spring Constant Factor = 1.0
2 - 17
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Smoothing
Spring Constant Factor = 0.1
2 - 18
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Smoothing
Spring Constant Factor = 0.05
2 - 19
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Smoothing
Spring Constant Factor = 0
2 - 20
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Smoothing
Smoothing on Quads
(rpsetvar 'dynamesh/spring/all-element-type? #t)
2 - 21
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Smoothing
The rpsetvar command is not used here. Smoothing is not applied automatically on quad/hex meshes.
2 - 22
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Layering
Constant Height z
Constant Ratio: z
z
Useful for uniform layer height Maintain a constant ratio of cell heights between layers Useful when layering is done in curved domains (e.g. cylindrical geometry).
Split if: Collapse if:
2 - 23
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Layering
2 - 24
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Layering
2 - 25
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Remeshing
Sizing Function Controls: Resolution: determines the size of the background bins used to evaluate the size distribution with respect to the minimum characteristic length of the current mesh. Sizing Function Variation Rate: How the background mesh increases in size (from the boundary to the interior) [1,+inf] Distance Threshold: Is the degree of polynomial that handles the size variation of the background cell size. (values in [-1,1]). Size Remesh Interval: How often the remeshing is done based on min and max cell volume.
2 - 26
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Remeshing Meaning of Variation Rate: A value of -0.5 means that the minimum mesh size (cell edge length) in the interior is half of the mesh size at the boundary, A value of 50 means that the maximum mesh size in the interior can be 50 times higher than the mesh size at the boundary. Meaning of Distance Threshold: The higher the value, the slower the change of the mesh size close to the boundary. A threshold value of 0 corresponds to linear in-/de-crease from the boundary. Negative threshold values enforce a faster (than linear) in-/de-crease at the boundary. Default Values work fine most of the time. 2 - 27
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Remeshing
Minimum Cell Volume: mark cells for remeshing if their size gets smaller than this value Maximum Cell Volume: mark cells for remeshing if their size gets larger than this value Maximum Skewness: mark cells if their skewness increases this value z z
Use 0.9 for tet mesh and 0.75 for tris
2 - 28
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Remeshing
No Smoothing Effect of Size Remesh Interval (SRI) z z
SRI = 10 Note that cells adjacent to moving wall get stretched.
2 - 29
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Remeshing
No Smoothing Effect of Size Remesh Interval (SRI) z z
SRI = 1 Note cells adjacent to wall don’t get stretched as much.
2 - 30
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Zones
2 - 31
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Zones - Stationary
Sets the nodes on a zone (either fluid or face zone) as stationary. Cell height: z z
z
z
Used for face zones For the remeshing of tet/tri, this height is used for boundary node distance. If layering, it will be used for ideal height. It should be roughly the same size as the initial mesh
2 - 32
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Zones – Rigid Body
Moves all nodes associated with that zone (cell or face zone) Nodes do not move relative to each other Motion Attributes: Motion can be specified by Profile or UDF. Center of Gravity (CG) and its location: specify if z
z
Profile uses position x, y, z. The position is measured relative to the CG location. Profile/UDF uses rotation
2 - 33
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Zones – Rigid Body
Mesh Options Cell height: z
z
z
For the remeshing of tet/tri, this height is used for boundary node distance. For layering, it will be used for ideal height. It should be roughly the same size as the initial mesh
2 - 34
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Zones - Deforming
Geometry Definition z z
Required for remeshing and smoothing A simple Cylinder and Plane is built in.
Cylinder requires Origin and Axis Plane requires any point on the plane and a normal vector
z
Normal vector can point either direction
User-Defined for other geometries
Deforming is NOT required if the adjacent cell is layering.
2 - 35
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Zones - Deforming
Meshing Options z z z z
Smooth: If smoothing is required Remeshing: If remeshing is required Expand until Contract until
2 - 36
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Zones - Deforming deforming
Smoothing and Remeshing applied on deformed face zones.
deforming
deforming
2 - 37
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Zones - Deforming
Smoothing is not selected Only Remeshing is applied. This looks much better. In some 2d cases, like this one, it may be necessary not to select Smoothing. In 3d cases, Maximum Skewness is also used, which prevents this problem. 2 - 38
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Dynamic Zones – User-Defined
If nodes move relative to each other, will need UDF
2 - 39
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Motion Specification
2 - 40
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
In-Cylinder Motion
For any simple sinusoidal (singledegree, rigid-body, and prescribed) motion, we can use the built-in piston motion:
A L
ps
L
θ c
Valve/Piston Axis A 2 - 41
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Table Profile
For any type of rigid-body, single-degree, and prescribed motion, you can use a profile table having the following format: ((profile_name_1 3 point) (time 0 1 2) (x 2 3 4) (v_y 0 -5 0)) ((profile_name_2 3 point) (time 0 1 2) (omega_x 2 3 4))
where, {“time”,“angle”}; { "x", "y", "z"}; {"v_x", "v_y", "v_z"}; {"theta_x", "theta_y", "theta_z"}; {"omega_x", "omega_y", "omega_z"}; Angle = crank angle
2 - 42
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
UDFs
Fluent also provides the following macros for DM calculations: z z z
DEFINE_CG_MOTION DEFINE_GEOM DEFINE_GRID_MOTION
2 - 43
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
DEFINE_CG_MOTION Macro
Used to define the motion of the center of gravity for rigid body motion z z
Macro: DEFINE_CG_MOTION ( name, dt, vel, omega, time, dtime) Argument types: z z z z z
Used for un-prescribed and prescribed motion Multiple-Degree of freedom
void *dt (dynamic thread pointer; common in all macros) real vel[] (array that returns the CG velocity) real omega[] (array that returns the ω of the CG) real time (time) real dtime (time step)
Function returns: void
2 - 44
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
DEFINE_CG_MOTION Example #include "udf.h" #include "dynamesh_tools.h" static real v_prev = 0.0; DEFINE_CG_MOTION(piston, dt, vel, omega, time, dtime) { Thread *t; face_t f; real NV_VEC (A); real force, dv;
/* compute pressure force on body by looping through all faces */ force = 0.0; begin_f_loop (f, t) { F_AREA (A, f, t); force += F_P (f, t) * NV_MAG (A); } end_f_loop (f, t) /* compute change in velocity, i.e., dv = F * dt / mass velocity update using explicit euler formula */ dv = dtime * force / 50.0; v_prev += dv; Message ("time = %f, x_vel = %f, force = %f\n", time, v_prev, force);
/* reset velocities */ NV_S (vel, =, 0.0); NV_S (omega, =, 0.0); if (!Data_Valid_P ()) return;
/* set x-component of velocity */ vel[0] = v_prev;
/* get the thread pointer for which this motion is defined */ t = DT_THREAD ((Dynamic_Thread *)dt); }
2 - 45
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
DEFINE_GEOM Macro
The DEFINE_GEOM macro is used to define geometry in a deforming zone Macro: DEFINE_GEOM ( name, d, dt, position) Argument types: z z z z
char name Domain *d void *dt real *position (this matrix is overwritten with the node position on the boundary)
Function returns: void
2 - 46
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
DEFINE_GEOM Example /************************************************************ * * defining parabola through points (0, 1), (1/2, 5/4), (1, 1) * ************************************************************/ #include "udf.h" DEFINE_GEOM(parabola, domain, dt, position) { /* set y = -x^2 + x + 1 */ position[1] = - position[0]*position[0] + position[0] + 1; }
The new position (after projection to the geometry defining the zone) is returned to FLUENT by overwriting the position array
2 - 47
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
DEFINE_GRID_MOTION Macro
Useful when defining the position of the nodes individually, e.g. fluidstructure interaction. DEFINE_GRID_MOTION ( name, d, dt, time, dtime) Argument types: z z z z z
char name Domain *d void *dt real time real dtime
Function returns: void
2 - 48
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
DEFINE_GRID_MOTION Example
Case: Specify the deflection of a beam based on local coordinate x and time t according to − 10 .4 x sin( 27 .178 t ), x > 0.02
ω ( x, t ) = {
0, x < 0.02
Node position is updated based on:
r n +1 = r n + Ω × r n Δt
2 - 49
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
DEFINE_GRID_MOTION Example /********************************************************** * * node motion based on simple beam deflection equation * compiled UDF * **********************************************************/ #include "udf.h"
NV_S (omega, =, 0.0); NV_D (axis, =, 0.0, 1.0, 0.0); NV_D (origin, =, 0.0, 0.0, 0.152); begin_f_loop (f, tf) { f_node_loop (f, tf, n) { v = F_NODE (f, tf, n);
DEFINE_GRID_MOTION(beam, domain, dt, time, dtime) { Thread *tf = DT_THREAD (dt); face_t f; Node *v; real NV_VEC (omega), NV_VEC (axis), NV_VEC (dx); real NV_VEC (origin), NV_VEC (rvec); real sign; int n;
/* update node if x position is greater than 0.02 and that the current node has not been previously visited when looping through previous faces */ if (NODE_X (v) > 0.020 && NODE_POS_NEED_UPDATE (v)) { /* indicate that node position has been update so that it's not updated more than once */ NODE_POS_UPDATED (v);
/* set deforming flag on adjacent cell zone */ SET_DEFORMING_THREAD_FLAG (THREAD_T0 (tf));
omega[1] = sign * pow (NODE_X (v)/0.230, 0.5); NV_VV (rvec, =, NODE_COORD (v), -, origin); NV_CROSS (dx, omega, rvec); NV_S (dx, *=, dtime); NV_V (NODE_COORD (v), +=, dx);
sign = -5.0 * sin (26.178 * time); Message ("time = %f, omega = %f\n", time, sign);
} } } end_f_loop (f, tf); }
2 - 50
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Summary
Mesh schemes available z z z
If there is relative motion between the boundary and its adjacent cell zone, Fluent will automatically choose the appropriate mesh scheme z z
Spring Smoothing Layering Remeshing
If the adjacent cell type is hex/quad, or wedge, it will use layering. If the adjacent cell type is tet/tri, it will use Spring Smoothing and Remeshing
The initial mesh needs to be decomposed according to the mesh scheme desired. Motion can be specified to face zones as well as to cell zones. Motion can be defined using profile, built-in in-cylinder piston profile, or UDF Motion can be prescribed or un-prescribe
2 - 51
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Step-by-Step Setup Procedure
2 - 52
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Smoothing
2 - 53
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Smoothing 1cm
sides 1
V_y (m/s)
0 1cm -1
0
.005
.01
V_y
.015
.02
cells-tri
Time (s)
bot 2 - 54
0.07cm
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Smoothing Step 1: Select Unsteady Solver Define Æ Solver
2 - 55
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Smoothing Step 2: Activate Dynamic Mesh and Select Mesh Methods Define Æ Dynamic Mesh Æ Parameters
2 - 56
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Smoothing
Step 3: Define Load Profile z
Write a profile file
((v_y 5 point) (time 0 .005 .01 .015 .02) (v_y 0 1 0 -1 0))
1
V_y (m/s)
0 -1
0
.005
.01
.015
.02
Time (s)
z
Read the profile
Define Æ Profile
2 - 57
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Smoothing
Step 4: Define Dynamic Zones z
Rigid Body motion
V_y cells-tri
bot 2 - 58
0.07cm © Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Smoothing
Step 4: Define Dynamic Zones z
Deforming side walls
sides
2 - 59
0.07cm © Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Smoothing Step 5: File Æ Write Æ Case Step 6: Mesh Motion Solve Æ Mesh Motion
2 - 60
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Layering -1
Layering takes place at the interface between tri and quad.
2 - 61
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Layering -1 1cm
sides y x
1
1cm
V_y (m/s)
0 .07cm
-1
0
.005
.01
.015
cells-tri
V_y
int
.02
Time (s)
cells-quad
0.1cm
.033cm
2 - 62
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Layering -1
Define Dynamic Mesh Parameters z
Default parameters for layering is fine
2 - 63
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Layering -1
Define Dynamic Zones z
Rigid Body Motion applied to the interface between tri and quad.
y x
.07cm
cells-tri
V_y
cells-quad 0.033
.033cm
int 2 - 64
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Layering -1
Define Dynamic Zones z z
Deforming sides No need to assign Deforming for sides attached to quad
sides y x
.07cm
2 - 65
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Layering -1
Final mesh motion.
2 - 66
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Layering -2
How to setup up when layering starts from bottom wall? This requires motion of quad cells and use of stationary on the bottom wall.
2 - 67
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Layering -2
Define Dynamic Zones z
Rigid Body Motion to Quad Cell Zone
y x
V_y cells-quad 2 - 68
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Layering -2
Define Dynamic Zone z
ALL nodes on quad moves unless declared as stationary. When declared as stationary, there will be relative motion between boundaries of the quad; therefore, layering will take place. y x
cells-quad .033cm 2 - 69
bot © Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Layering -2
Dynamic Mesh Zone Assignment z
IF control of height for the tri is desired, specify Rigid Body motion to the interface and specify ideal height.
y x
.07cm
V_y cells-tri cells-quad int
2 - 70
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Layering -2
Dynamic Mesh Zone Assignment z
Deforming sides attached to tris.
sides-tri y x
.07cm
2 - 71
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Layering -2
Final mesh motion.
2 - 72
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Remeshing & Layering -3
How to setup if layering and remeshing starts and stops at different times? This requires two profiles, one for the quad and another one for the interface.
2 - 73
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Simple Remeshing & Smoothing
Need to specify two profiles.
Note: Details of setup not shown
int 1
cells_quad 0 (m/s)
cells-quad
-1 0 .02
.005
.015 ((cells-quad 5 point)
-1
int (m/s)
.01
(time 0 .005 .01 .015 .02)
Time (s)
(v_y 0 -1 0 1 0)) -0
((int 7 point) (time 0 .005 .005 .01 .015 .015 .02)
-1
(v_y 0 -1 0 0 0 1 0)) 0
.005
.01
.015
.02 Time (s) 2 - 74
Profile File
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Non-Conformal
What if we have non-conformal interface?
It is used for: z
z
Closing valves. Must have it between layering and remeshing.
2 - 75
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Non-Conformal
DefineÆGrid Interfaces z z z z
Select int_quad under Interface Zone 1 Select int_tri under Interface Zone 2 Specify name under Grid Interface Click on Create
cells-quad
cells-tri
Note: Motion Specification to the bottom walls are not shown.
int-quad
2 - 76
int-tri
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Non-Conformal
Define Dynamic Zones z
Only the sides that is part of the tri should be declared as Deforming.
cells-quad
int-quad 2 - 77
cells-tri
int-tri
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Non-Conformal
Define Dynamic Zones z
Define sides as Deforming
cells-tri
side-tri
2 - 78
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Simple Inserting a Layer
How to insert a new layer?
2 - 79
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Inserting Boundary Layer
Events is used to insert layering at crank-angle of 40 degrees and removed at crank angle of –40 (320 degrees).
cyl-side: deforming
piston: rigid-body piston motion 2 - 80
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Tips and Tricks
2 - 81
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Completely Closing a Valve
There are two ways to completely close a valve. z z
The most common method is to delete non-conformal interface. Changing cell type from fluid to solid.
The above can be performed via the Events (DefineÆDynamic Mesh ÆEvents) But since events were implemented mainly to open and close valves in IC applications, it is in terms of Crank Angle! But it is easy to translate or transform our time into Crank Angle.
2 - 82
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
Completely Closing a Valve High pressure
How to close a valve as shown on the right? You need to create the mesh with the non-conformal interface as shown.
valve
v_ y interface-1
-1
v_y (m/s)
interface-2
-0
-1 0
.005
.01
.015
.02
Low pressure
Time (s) 2 - 83
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Completely Closing a Valve
Define Global Controls and Motion Specification For ease, get 1-to-1 correspondence between Crank Angle (degrees) and time (seconds). z
To do this, specify Crank Shaft Speed of 0.1666667 rmp
Specify the period for the oscillation, which is 0.02 seconds, as Crank Period = 0.02 deg The simulation will be run at time step size of 5e-5, so enter 5e-5 for Crank Angle Step Size Put any number > 0 for Piston Stroke and Connecting Rod Length
2 - 84
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Completely Closing a Valve
After setting up Global Parameters and defined Dynamic Zones, you need to define events in DefineÆDynamic MeshÆEvents In this example, at initial mesh, the valve is assumed closed, so enter 0 under At Crank Angle (deg) We will keep it closed for about 0.0001 second to make sure we get at least one step while it is closed. 2 - 85
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Completely Closing a Valve
HVAC Register Temperature plot
2 - 86
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Completely Closing a Valve
HVAC Duct Non-Conformal Interface is used
2 - 87
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Completely Closing a Valve
Another example of valve
2 - 88
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Min and Max Volumes - 1 For the remeshing scheme, what is the best way to determine Minimum and Maximum Cell Volume? Plot histogram of cell volume. Plot Æ Histogram
%
Select Min and Max roughly as shown on the right figure. But this will give plot of all cells zones. 2 - 89
Min
Max © Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Min and Max Volumes - 2
To find min and max volume in a given cell zone, z
z z
Select the cell zone under Zones Name in Dynamic Zones panel Click on Zone Size Info.. But don’t click on create!
For Minimum Volume in the remeshing parameters use a value slightly larger than reported above. For Maximum Volume in the remeshing parameters use a value slightly smaller that reported above.
2 - 90
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Current Limitations
Can’t have two deforming face zones attached. For deforming face zone, one need to have complete edge-loop You may also need to use deforming on a face zone if the adjacent cell zone is only being smoothed.
2 - 91
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Examples
2 - 92
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Passing Cars
2 - 93
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Passing Cars Prism layers move with the car.
2 - 94
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Check Valves
Fluid-structure interaction Spring loaded valve. Determine ball position as a function of flow forces z
Implemented through a UDF
2 - 95
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Check Valves
The max displacement of the ball was known to be small. So only smoothing is used.
2 - 96
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Flow Control Valves
2 - 97
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Fuel Injectors
Transient flow rates Cavitation Flow forces
Pure Layering
2 - 98
© Fluent Inc. 11/7/2005
Fluent User Services Center
Fuel Injectors
www.fluentusers.com
FLUENT Software Training DM Model March 2003
Fuel Injectors
Velocity Contours
2 - 99
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Compressors
Spring loaded valves Valve motion coupled to the flow solution via a UDF
2 - 100
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Compressors
As the piston moves to BDC, intake valve opens and exhaust valve closes As the piston moves to TDC, intake valve closes and exhaust valve opens
2 - 101
© Fluent Inc. 11/7/2005
Fluent User Services Center
FLUENT Software Training DM Model March 2003
www.fluentusers.com
2-Stroke Engines
Premixed combustion
Mesh motion
2 - 102
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
4-Stroke Engines
2 - 103
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Positive Displacement Pumps
2 - 104
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Gear Pumps
2 - 105
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Volumetric Pump
Pump diameter of 6 cm Water Eccentric (offset) rotor z
All-hex grid z
Blades move in and out of the rotor 100,000 cells
Mesh motion specified via user-defined function z
Constant RPM of 1,500
2 - 106
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Volumetric Pump
Geometry and motion
2 - 107
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Volumetric Pump
Pressure contours
2 - 108
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Vibromixer
Contours of Velocity
2 - 109
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Vibromixer
Pure Layering
2 - 110
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Store Separation
Fluent Versus Wind Tunnel
2 - 111
© Fluent Inc. 11/7/2005
Fluent User Services Center www.fluentusers.com
FLUENT Software Training DM Model March 2003
Store Separation
Contours of pressure Note partition interface move. z
Dynamic partitioning is performed.
2 - 112
© Fluent Inc. 11/7/2005
Swimming Dolphin!
Flying Fly!
View more...
Comments
