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Old   October 25, 2012, 16:41
Default Squeeze Flow
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Michael Anderson
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Hi,
I'm attempting to model simple squeeze flow between 2 plates. I have created a simple rectangle in 2D with axisymmetric geometry, but am having problems getting it to run. Below is the geometry for the file with the specified boundary conditions.

[IMG] http://s3.beta.photobucket.com/user/...ryPic.png.html [/IMG]


I was told by customer support that I need to create a udf, define_cg_motion so I am trying to figure this out as I am new to fluent. Below is the udf I made and interpreted into the setup for the top plate.

# include "udf.h"
# include "dynamesh_tools.h"

DEFINE_CG_MOTION(wallmov, dt, vel, omega, time, dtime)
{
Thread *t;
face_t f;
vel[1]=.1;
}

I specified the system as a transient system with a .001sec time step and to run for 50 time steps.
Without the udf I am getting incorrect results and no visible motion of the top plate. When I try to specify the cg_motion for the top wall i am getting the error: Warning incorrect cg motion UDF wallmov on zone 7 (assuming no motion).
If anyone could help, it would be much appreciated because I have been struggling on this for awhile. Also if the problem is nearly clearly defined please let me know.
Thanks in advance!!!
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Old   October 26, 2012, 02:41
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Daniele
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Hi,
you have to move your plate in -x direction!
vel[1] is movement in y direction, with vel[0] you will move your plate in x direction; I think you have to specify a negative velocity to move in -x direction; vel[2] is movement in z direction.
Try this:

Code:
# include "udf.h"
# include "dynamesh_tools.h" 

DEFINE_CG_MOTION(wallmov, dt, vel, omega, time, dtime)
{
Thread *t;
face_t f;
vel[0]=-0.1;
vel[1] = 0.0;    
vel[2] = 0.0;
}
Very important:
you have to compile this udf, interpreting it will not work with cg motion macro!
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Old   October 27, 2012, 15:13
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Michael Anderson
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Thanks so much for the help, I finally got it working!!!

I have one more question that should be simple but i cant find the answer anywhere. After previewing the mesh motion and the two walls converging how do I reset the geometry and mesh to the beginning? I tried to initialize the solution, but that only resets the iterations and time step and not the geometry. So when I try to run it again I get the error of a negative volume.
Thanks again!
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Old   October 28, 2012, 05:14
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Quote:
Originally Posted by mjaisit View Post
Thanks so much for the help, I finally got it working!!!

I have one more question that should be simple but i cant find the answer anywhere. After previewing the mesh motion and the two walls converging how do I reset the geometry and mesh to the beginning? I tried to initialize the solution, but that only resets the iterations and time step and not the geometry. So when I try to run it again I get the error of a negative volume.
Thanks again!

I think that after previewing the motion you cannot reset the position of the plate..I remember I read this somewhere in the past: save cas and dat files before previewing the motion!
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