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moloykb September 12, 2012 05:20

Dynamic mesh issue
 
1 Attachment(s)
Dear all,
I am trying to simulate the flow through a artery in the presence of stenosis with surface irregularities. The artery wall is assumed to oscillate with a velocity of sinusoidal variation. In order to define the motion of the wall I am using the Dynamic mesh feature of Fluent with the following compiled udf to define the motion of the wall.

#include "udf.h"

DEFINE_CG_MOTION(wave, dt, vel, omega, time, dtime)
{
vel[1]=-.0001*7.543*sin(7.543*time);
}
For the unsteady simulation I am using a time step size of 0.0001 sec and as a mesh method I am using Layering approach with a split and collapse factor of 0.4 and zone type as rigid body.
But unfortunately when I try to run the simulation it shows the error Update-dynamic mesh failed: negative cell volume detected.
Please help me.

cfd seeker September 12, 2012 10:21

try reducing your time step size and also play with dynamic mesh parameters, also turn on smoothing

moloykb September 13, 2012 00:32

Dear cfd seeker
thanks for your reply. I have already reduced the time step upto 0.000001 sec, but till the same problem exists.Regarding the parameters how to choose the proper value of those.

nimbus1947 September 13, 2012 03:38

Try using triangular mesh and use re-meshing instead of layering.

If you insist on going with quad mesh try the following
1. Set the udf motion for the fluid (the quad mesh region)
2.Set the boundary as stationary.

cfd seeker September 13, 2012 06:03

Quote:

Originally Posted by nimbus1947 (Post 381535)
Try using triangular mesh and use re-meshing instead of layering.

If you insist on going with quad mesh try the following
1. Set the udf motion for the fluid (the quad mesh region)
2.Set the boundary as stationary.

which boundary to set as stationary?

moloykb September 13, 2012 06:17

dear nimbus1947
how to set the udf motion for the fluid zone and what is the stationary boundary. Would u please elaborate something?

nimbus1947 September 13, 2012 07:56

upload the picture of your full domain with boundary names.

fluentworkshop September 24, 2012 07:02

Hi guys
Cell height of wall (in dynamic mesh zones) must not be zero.
or you must use another wall as stationary and also quad zone must be move with same udf.

cfd seeker September 24, 2012 12:07

Quote:

Originally Posted by fluentworkshop (Post 383304)
Hi guys
Cell height of wall (in dynamic mesh zones) must not be zero.
or you must use another wall as stationary and also quad zone must be move with same udf.

didn't get your point?


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