Piston motion
 

Hello,

I am trying to do CFD analysis on a cylinder with piston who will move up and down.
Attached there are some print screens.
I followed the tutorial "ball scheck valve" for the boundary conditions.

But would like to introduce a displacement expression : 30*sin(2*PI/t).
I don't arrive to introduce this kind of expression, I only find velocity in boundary conditions.

Is there an other way very easy to move this piston up and down ?

thank you very much for your help.