Learning Forum

[MMary]

Hi, in the Fluent Theory guide for v 2021 R2, under section 14.5.23 regarding DDPM it states "no Discrete Element Method (DEM) type collision treatment is applied, which would otherwise allow the efficient simulation of systems with a large number of particles". Does this mean that the DEM model cannot be used with DDPM?

[Murari Iyengar]

Hi MMary DEM can be used with DDPM. By using DEM with DDPM, you can efficiently simulate systems with large number of particles.

[MMary]

Thanks for replying but if that's the case, what was meant by the above statement in the theory guide? I'm struggling to get DEM to work well with DDPM. It seems to run okay with DPM-DEM but not DDPM.

[Rob]

DDPM reverts to the Eulerian multiphase model as particle concentrations get high. I suspect that then means there are no particles for DEM collisions to occur. What are you trying to model?

[MMary]

Thanks for the reply. I'm modelling a closed cavity that's differentially heated with particles inside. The cavity is 10x10x10 mm and the particles are approx. 80 micrometers in diameter. The number of particles is typically 1000-10,000 but below 10% volume fraction. I am using DDPM to include the additional forces such as wall lubrication and also want to model collision. The particles form structures over time so I expect to find regions where particle concentration is high and other regions where it's low.

[Rob]

You're in the grey area where Fluent's DEM isn't quite what you want, nor is DDPM or Eulerian. Have a look at Ansys Rocky coupled with Fluent: full DEM code with flow.

[MMary]

Thank you. Is Ansys Rocky the same as Rocky DEM? Will it be available with an academic license?

[Rob]

It's much the same code, but the version ID's are slightly out of sync, otherwise the interface is the same. No idea about the licencing as I just ask nicely and get whatever I want: your account manager will know.