CFD-DEM Tutorial – Vacuum Excavator

We created a tutorial for a coupled CFD-DEM simulation using LIGGGHTS and OpenFoam. Please check out the video file on youtube. I hope you find it helpful. 

This is a full tutorial, starting with the CAD model, the meshing with snappyHexMesh, the boundary conditions and the DEM simulation to the final coupled CFD and DEM simulation using CFDEM. You can also follow the tutorial on this block. The major steps are explained and shown via screenshots. 

A coupled simulation contains 3 major steps 

  1. The geometry generation. Here blender will be used for this but also every CAD system can be used to model your maschine or process geometry. 
  2. A CFD simulation must be set up. A mesh is needed to run the simulation. Here openFoam will be used. The mesh is generated using snappyHexMesh. Because openFoam can be challenging from its interface, we were using helyx as a front end. 
  3. The DEM simulation must be set up in liggghts. The coupling must be activated. After this liggghts and openFoam are exchanging forces and velocites. 
  4. The results are post-processed in paraview
The software used in this tutorial is blender 2.8, openFoam 4.1, helyx 2.4.0, Liggghts 3.8.0 and Paraview 5.0.0

The download link to the CFD-DEM tutorial can be found under the the end of the page.



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Blender 2.8 generating the mesh
blender can be used to generate watertight meshes of surfaces

The opensource software “blender” can be used instead of a CAD program to design the geometries you need for your simulation. I’m using the version 2.8xx here. Blender is a very functional and powerful tool, which needs a bit of time to get used to. However, after a while it gets very efficient to use blender to model geometries or do basic changes like adding a plates or resizing parts of the structure. 

If you are working with complex industry models, it’s probably the best to use a CAD model first. This model then must be exported as an STL file. STL files are triangulated surface meshes. These meshed are used in the CFD and the DEM simulation for any maschine structure, the in- and outlets and the other boundary conditions. 

STL files can also be opened in blender and remodeled if necessary.  

helyx 2.4.0 STL import
The fist step in helyx is to import the stl files generated in blender

The created STL files, each for every functional face, are loaded into helyx. Helyx is an open source frontend for openFoam. Hence it works only with openFoam 4.1 I’m using OF 4.1 here, too. 

Helyx is used here for the the creation of the mesh and the setup of the boundary condition. A test simulation well also useful out of helyx. 

The part are loaded and should now be visible on the right side of the window.  

Generating a base mesh with blockMesh
Helyx ist used to generate the base mesh
Openfoam blockMesh
The blockMesh cell size should be equal in every direction
local refinements in helyx
Parts are set to have a local refinement in openFoam snappyHexMesh.

2 responses to “CFD-DEM Tutorial – Vacuum Excavator”

  1. Bo Zhang says:

    Hi Hendrik,

    Thanks for the shearing and explanation of your cases. I am now working on my PhD project, which is about fluid flow with particles in rock fractures(CFD-DEM). Your tutorials really helped me a lot.

    These days, I want to track the trajectory of a specific particle in a lot of particles, and get its time-dependent velocity and the drag force imposed on it. Could you please give some advice?

    Thanks and regards,

  2. Ferenc Safranyik says:

    Hello Hendrik,

    first of all congratulations for your work! I think it is very appreciated by enginners and researchers working with particulates. I am a similar person, who has interested in this topic. I have started my DEM carrier by EDEM then I started working with YADE. Now I am interested in CFD-DEM coupling capabilities of LIGGGHTS and OpenFoam and I try to learn how these systems are working. Can you provide an installation tutorial for HELYX-OS and OpenFoam 4.1 which are used in your tutorial?

    Thanks in advance, Feri

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