CFD Online Discussion Forums

CFD Online Discussion Forums (
-   FLUENT (
-   -   Boundary condition for vibrating disk (

Apple March 4, 2009 23:40

Boundary condition for vibrating disk

I'm doing about the ultrasonic piezoceramic disk vibrating under water in the tank with no feeding water. Then waves propogate from the disk upward to water surface. The thing is I am not sure how to set the boundary condition at the disk. Could it be velocity inlet or deforming wall? The disk motion is in y direction (2D); the deformation is governed by y(t)=asin(2*PI*f*t)and velocity is Vy(t)=2*PI*f*a cos(2*PI*f*t). Which one should I use?

Thank you very much....

mAx March 5, 2009 04:47

Re: Boundary condition for vibrating disk
Let your disk as wall in boundary condition.

Enable deforming mesh

describe the motion in an UDF

then in the deforming mesh panel, choose your udf your describing the motion of your disk

Apple March 5, 2009 07:30

Re: Boundary condition for vibrating disk
Thank you very much Max,

In wall boundary condition panel, do I need to put any udf motion for the wall or just leave it as 0 and only add udf in deforming mesh panel? I have to enable dynamics mesh,right? and then specify the zone by choosing deforming or User-define under type? One more thing I'm not quite sure how to write udf, should I use Define_Geom or define_grid_motion? Can anyone help me suggesting how to write it, I dont know that much about writing udf.

mAx March 5, 2009 08:38

Re: Boundary condition for vibrating disk
set your disk as wall (default set up)

in Deforming mesh, set your disk with rigid body motion, and then Motion attribute with your udf, in which you should use DEFINE_CG_MOTION()

In the tutorials, there is one about MDM with an udf. Get inspire in it

All times are GMT -4. The time now is 11:35.