Learning Forum

[Chris_g]

Hello,

I have recently upgraded from ansys 21 R2 to 22 R2. Since the upgrade all of my DEM cases diverge, usually within the first few time steps. On fluent 21 the same cases are running fine. This happens both on my local machine (Windows 10) and our HPC (Linux).

I usually simulate reactive fluidized beds with high solid loading, however on 22.2 even for low solid loadings with inert particles and deactivation of species and energy equation the simulation still diverges.

Is there a known issue on the version 22.2 that causes problems with DEM simulations?

Thanks for your help!

Chris

[Rob]

I tend not to use DEM in Fluent, and instead use Ansys Rocky as it's significantly more computationally efficient and stable. For a fluidised bed in Fluent I'd use Eulerian over DEM. Are you running hi-res tracking on the DPM model? 

[Chris_g]

Thank you for your quick reply.

I will check with our IT department if Ansys Rocky is available for me. If so this might be a better solution.

We are using DEM to get a more detailed picture of the bed and would prefer to stick with it, if it is possible to get it to run.

Currently I am not using hi-res tracking. I did some tests with it and found that convergence is even worse with hi-res turned on.

[Rob]

I know we've been working on the DPM model numerics so there may have been a change that's not working well with the DEM part. There's nothing in the release notes, but check through for 22R1 and 22R2 in case you've got a model switched on that I've missed.