I don’t see how the provided setup could run. For starters, the ‘side inlet’ in the geometry is open so it should be a mass inflow – not an ‘eb’ boundary condition – and therefore it cannot be used with DEM particles.
As I always suggest, start simple and add complexity to the setup in a systematic approach. You will never figure out what’s wrong if you throw everything into the initial setup and it doesn’t run.
Attached is your setup, simplified for non-reacting flow. I’ve tested this setup on both CPU and GPU.
dem-debug.tar (20 KB)
- I made the domain a little taller (0.43 m → 0.48 m) so that the width, depth, and height and all nicely divisible by 24-cube grids. ‘Nice grids’ make it easier on the MLMG solver.
- The side inlet – as defined in the original inputs with the provided CSG geometry – will not work for DEM. I papered over the inlet to get the case to run, but the geometry has to be modified if you want to bring DEM particles into the domain there.
- You used a fairly stiff spring constant at 2.5K. I reduced it to 25. which works for as much as I’ve tested. You’ll have to live with long times to solution if you roll back to 2.5K as the DEM time step is around 1.e-8 seconds.
The below figure shows a few different ‘grid’ decompositions. Note that “more” isn’t always “faster” and again, a single grid on a single GPU is about 5x faster than the best preforming CPU case.
