I'm running into a strange problem. I am running a transient flow simulation in Fluent. In this simulation there is a moving flap in the outflow of a pipe. For the moving part I am using dynamic meshing. I played around with the settings and the initial mesh, so that it seemed appropriate for the dynamic meshing.
When I preview the dynamic meshing process in Fluent, everything seems to be ok. No faults or errors and the mesh looks fine. But when I start the calculation process (same time step as in the preview process) after 40 to 50 time steps, I get the error message of negativ cell volume. This doesn't happen in the preview process. There the mesh behaves fine for 500 time steps.
What could that be ?