Hello,nI agree with that you are able to do this motion from the boundary condition. You just need to convert your force table into velocity table. Also as you have a clear sine wave, you don't need to use the table, just use an equation.nHowever, your UDF should still work and I can't recognise an obvious mistake. My question is, how did you find out it is not moving? you will not actually see the wall motion but you can simply monitor the velocity at the wall and see if it oscillates as intended or notnYasser n