Extending DEM with CFD

Submitted by jojo on Mon, 05/21/2018 - 11:49

Hi

i'm currently trying to extend a working DEM-simulation with CFD.
The setting is like this: particles get moved trough a chute and a conveyor belt via DEM and end in a pipe where they should get sucked off via CFD. From what i‘ve understood by now, i need a mesh of the enviroment to get the CFD-part working. My question here is: do i need to mesh the whole enviroment or only the pipe where the particles get sucked off? When i only need the pipe, does it have to be closed on the ends?

I plan to mesh with snappyHexMesh and the .stl files which are already used for DEM. Is there anything else i need to keep in mind for this?

Greetings,
Johannes

Forums:

paul | Tue, 05/22/2018 - 09:03

You do not have to mesh the entire domain. The outlet should ideally be open in the STL used for LIGGGHTS, for OpenFOAM it depends on your mesher.

jojo | Thu, 05/24/2018 - 19:36

Thank you for your answer!
I use different .stl files for LIGGGHTS and OpenFOAM, one with closed inlet and outlet for meshing, and an open one for DEM.
I can sucessfully run the snappyHexMesh and see my results in paraview, but im not sure weather the outcome is 100% right or i still have to do some work there -
the created polyMesh in the directory constant does not contain the boundaries i need, only "defaultFaces". The boundaries in 0.01 and 0.02 generated while meshing are correct. Is this normal or wrong?
When i open the .foam file in paraview, what i see on time 0 is the mesh generated by blockmesh, on time 0.01 its the mesh from snappyHexMesh.

Also, when trying to solve the CFD part, every result is zero.

Greetings, Johannes

paul | Fri, 05/25/2018 - 12:18

> The boundaries in 0.01 and 0.02 generated while meshing are correct. Is this normal or wrong?
>Also, when trying to solve the CFD part, every result is zero.

This is normal, just copy the polyMesh from 0.02 into constant and you're fine. Alternatively run snappyHexMesh -overwrite to do this automatically. And please read up on how snappy works - it will be useful for the future.