Squeeze Flow

mjaisit · October 17, 2012, 16:46

I am trying to model a 2d version of squeeze flow between two plates. I tried to make it as simple as possible since I am new to fluent. I made a simple 5x.5 meter rectangle for the geometry in the xy axis and defined a finer mesh. For the boundary conditions I specified the top as a moving boundary condition moving in the -y direction at .1 m/s, my left and right boundary conditions as outflows, and the bottom as a stationary wall. I am obviously doing something wrong because when i create an animation of the contours of x velocity is does not change with time. If anyone has any suggestions it would be greatly appreciated.

Marion · October 18, 2012, 07:55

Hi,
Well it could be an issue with the time step...
Is your moving wall actually moving when you play the animation?
How much is the constant X velocity given on the contours?
Marion.

mjaisit · October 18, 2012, 16:16

I have the time step set to .1 sec with the total run time as the time taken for the moving wall to reach the stationary wall. Do I need a smaller time step? The wall boundary condition is not moving in the animation. I wasnt sure if the animation would show it or if it would just show the change in the contours of the properties that were being tracked. I should have specified what i was talking about with the x velocity contours, there are actually no contours. It is showing the entire rectangle as the same velocity and does not change with time. I am really confused because pressure contour animation plot looks realistic.

Marion · October 19, 2012, 05:09

Hi,
You should see the moving wall moving with time! if it's not, then it is normal that the velocity doesn't change.
How come the wall doesnt move? have you checked the mesh motion with the "preview mesh motion" feature in the MDM panel?
Marion.

mjaisit · October 24, 2012, 16:34

I have contacted customer support also for help and was told that I need to use define_cg_motion. So I take it that specifying the boundary condition as a moving wall is not enough to acutally make it move. I am going to consult the user manual for writing a udf for this.

October 17, 2012, 16:46	Squeeze Flow	#1
mjaisit New Member Michael Anderson Join Date: Oct 2012 Posts: 14 Rep Power: 13	I am trying to model a 2d version of squeeze flow between two plates. I tried to make it as simple as possible since I am new to fluent. I made a simple 5x.5 meter rectangle for the geometry in the xy axis and defined a finer mesh. For the boundary conditions I specified the top as a moving boundary condition moving in the -y direction at .1 m/s, my left and right boundary conditions as outflows, and the bottom as a stationary wall. I am obviously doing something wrong because when i create an animation of the contours of x velocity is does not change with time. If anyone has any suggestions it would be greatly appreciated.

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October 18, 2012, 07:55		#2
Marion Senior Member Marion Join Date: Jul 2012 Location: France Posts: 122 Rep Power: 14	Hi, Well it could be an issue with the time step... Is your moving wall actually moving when you play the animation? How much is the constant X velocity given on the contours? Marion.

October 18, 2012, 16:16		#3
mjaisit New Member Michael Anderson Join Date: Oct 2012 Posts: 14 Rep Power: 13	I have the time step set to .1 sec with the total run time as the time taken for the moving wall to reach the stationary wall. Do I need a smaller time step? The wall boundary condition is not moving in the animation. I wasnt sure if the animation would show it or if it would just show the change in the contours of the properties that were being tracked. I should have specified what i was talking about with the x velocity contours, there are actually no contours. It is showing the entire rectangle as the same velocity and does not change with time. I am really confused because pressure contour animation plot looks realistic.

October 19, 2012, 05:09		#4
Marion Senior Member Marion Join Date: Jul 2012 Location: France Posts: 122 Rep Power: 14	Hi, You should see the moving wall moving with time! if it's not, then it is normal that the velocity doesn't change. How come the wall doesnt move? have you checked the mesh motion with the "preview mesh motion" feature in the MDM panel? Marion.

October 24, 2012, 16:34		#5
mjaisit New Member Michael Anderson Join Date: Oct 2012 Posts: 14 Rep Power: 13	I have contacted customer support also for help and was told that I need to use define_cg_motion. So I take it that specifying the boundary condition as a moving wall is not enough to acutally make it move. I am going to consult the user manual for writing a udf for this.