Learning Forum

[Ruben Waeytens]

I am modeling the transport of a granular phase in a twin-screw configuration.
The geometry is shown below:

I have created a fully tetrahedral mesh with the periodic boundary conditions turned on:

The dynamic mesh was set up as follows:

The simulation runs smoothly for the first couple of iterations, but at a given moment in time, it crashes because a negative cell volume is detected.
I saved a case file just before the simulation crashes and noticed that the lowest quality cells (orthogonal quality smaller than 0.1) are located near the periodic boundary condition:

I have tracked the orthogonal quality during the simulations and it even becomes zero just before the simulation crashes. Mass was conserved.
I have already tried different things like reducing the time step (currently 5e-5s), or reducing the maximum skewness allowed before remeshing is done, without success.

What could be the reason that I obtained a negative cell volume with the current set-up?
Thank you in advance for your response.

Ruben

[Prashanth]

Not sure if it's late, you would need to increase the mesh resolution if you experience negative cell volume error, given the dynamic mesh conditions are setup properly.