[MFIX-DEM] how the particle interacts with undefined boundaries?

MFiX
#1

[MFIX-DEM] how the particle interacts with undefined boundaries (No-slip walls)? Is it the same with typical walls defined in geometry?

Are the parameters for a particle-wall interaction such as friction coefficients, spring constants and so on applied to undefined boundaries, too?

Additionally, in order for the particles to leave the domain, a pressure outlet boundary condition is the only way for boundary conditions?

Best,
Hakun

#2

MFIX always places walls at domain extents for DEM particles (and PIC parcels). This is not true for Eulerian phase (I.e., the fluid and TFM solids), therefore all boundaries must be fully specified when an STL geometry intersects the domain extents. For example, if you use an STL defining a cylinder for the geometry, and the cylinder extends past the top and the bottom of the domain, then you must specify boundary conditions on the top and bottom faces for the fluid, even if you want a solid wall. Conversely, Lagrangian solids “see” a wall by default.

DEM particles (and PIC parcels) can leave the domain only though pressure outflows and mass outflows. All other boundary conditions are treated as solid walls for Lagrangian solids.