Negative volume problems with mesh
 

All,

I am simulating a 2D model of a check/relief valve where the ball in the valve is oscillating in the Y-direction (up and down) due to the inlet velocity. Eventually I want to simulate valve chattering.

The problem I am encountering is when the ball touches he walls or get really close, I get a "negative volume" error.

Mesh:
Min Ortho quality is approximately 0.6
Max Ortho Skew is approximately 0.3
Max aspect ratio is approximately 3.8

Dynamic Mesh options:
Remeshing (I used diffusion with diffusion factor at 0)
Smoothing
6DOF
Implicit

I used a UDF to determine the rigid ball motion, which is only translation in the y-axis. When I initialize the problem and inspect the motion of the ball it moves well, however, when it reaches the boundaries, I get the error. Also, it does not stop at the boundaries and continue moving which is telling me there is something with the boundary conditions of the contact. I believe since the ball ouches the wall, the topology is separated???

What do I need to consider for the negative volume I am getting?

Any help would be appreciated.

Thanks