Dynamic Grid Remeshing causing Divergence?

Andrew Wick

I'm working on a problem with an object falling into water using the VOF model and the 6-DOF model with dynamic mesh. I am using the Fractional Step NITA method with compressible air. I also have a chunk of grid moving with the object, so all cell remeshing occurs far away.

At a certain point in the solution, the pressure field diverges and blows up. I noticed that this occurs after cell remeshing in the domain. If I turn cell remeshing off just prior to this, the solution does not diverge. The remeshing is not causing any skewed or negative volume cells to appear. This is happening to me consistently with 2 different object shapes (and thus, 2 different grids).

This problem only appears when I attempt to model compressible air flow. It does not happen with incompressible air flow.

Any ideas what could be causing this problem? Is there something in the algorithm fluent uses that would cause it to calculate things differently with remeshing turned on? Is there any way to fix it?

Thanks,