Eulerian Granular FLow Axisymmetric vs Planar mesh
 

Hello All,

I have been running simulations for a while using eulerian gas-solids flow. A crater (like a pit) forms in the dense particle phase, and over time this pit should stay there. You can think about it as if you stick a shovel in sand and remove a scoop of sand at the beach, a crater remains after the scoop is removed. Except in our simulation you are excavating the sand with a gas jet.

When I model this is an axisymmetric boundary (the bottom of the crater at the symmetry axis) the crater remains for about 0.5 seconds and then starts to fill in. When I model this in a 2D planar mesh the crater remains with very little change for over 1.5 seconds. Now, even though this is being simulated in two very different domains, the physics behind particle being able to form piles remains the same. This make is seem the issue is related to the axisymmetric simulation.

Has anyone run into this before? Does anyone know why numerical diffusion would be worse with the axisymmetric boundary condition than a 2D planar domain?

I found out the problem.

There is some sort of bug in the eulerian flow with axisymmetric boundary conditions. The particles move "unphysically fast" along the boundary. The people at fluent have told me this. Just wanted to spread the word.