IC piston motion - deforming meshes
 

I am trying to solve the ic engine problem. I am solving only motored flow in axi-symmetric geometry with flat piston. I observed that , if I start the simulation at TDC then as the piston reaches BDC, the velocity of the piston at BDC is not reduced to zero. The piston velocity reduces to zero after theta > 180 which is not acceptable. Can anyone explain as to how to come out of this situation ? Any hint/help is sincerely appreciated.