dynamic mesh
 

hello sir
I am trying to simulate a gas cylinder moving in tunnel has length 22 m .using dynamic meshing. to define regid body motion of the gas cylinder and I have assigned the air zone as deforming
I am getting follow error ..
Error: Update-Dynamic-Mesh failed. Negative cell volume detected.
I tried smoothing the mesh, which does helps for a while. But the error repeats again and again.

Please help me.
Thanks