# Squeeze Flow

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 October 25, 2012, 16:41 Squeeze Flow #1 New Member   Michael Anderson Join Date: Oct 2012 Posts: 14 Rep Power: 5 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!!!

 October 26, 2012, 02:41 #2 Senior Member     Daniele Join Date: Oct 2010 Location: Italy Posts: 992 Rep Power: 16 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!

 October 27, 2012, 15:13 #3 New Member   Michael Anderson Join Date: Oct 2012 Posts: 14 Rep Power: 5 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!

October 28, 2012, 05:14
#4
Senior Member

Daniele
Join Date: Oct 2010
Location: Italy
Posts: 992
Rep Power: 16
Quote:
 Originally Posted by mjaisit 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!

 April 21, 2015, 06:42 bad convergence #5 New Member   rim Join Date: Feb 2015 Posts: 2 Rep Power: 0 I'm a beginner in fluent and i'am trying to model a 2d version of squeeze flow between two disks. I made a simple rectangle(1x20) for the geometry in the xy axis and for the boundary conditions I specified the top as a outflow moving, the bottom as an axis , my left as symmetry and the right boundary conditions as velocity inlet (0.01 m/s).First of all I want to know if my geometry is convienient with my model ? Second in the simulation when i put a fine meshing i found a bad results and when i put a large mesh i found a good results and these are illogical .If anyone has any suggestions it would be greatly appreciated. Thanks all.

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