Generating a flow region with porous zones

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1

Hi,

I’m trying to set up a CFD simulation with (at least initially) some simplified ‘trees’ which are supposed to be porous. However, I’ve tried several different options and can’t really get to create a mesh that includes both the ‘enclosure’ and the ‘tree’ regions (the cylindrical ‘trunk’ pieces are supposed to be left empty), and I can either get a mesh of everything, of the enclosed space (without the trees) or an error.

What am I doing wrong?

Thanks!

2

Hi, @nleet,

For this simplified geometry, there’s a very straight forward way to configure the porous zones. You can use geometry primitives instead of adding volumes in your CAD geometry to represent the trees:

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However, this will only work with simplified geometries for the trees. More specifically, with cubes/parallelepipeds, cylinders and spheres.

Since you're planning to use more complex trees, I'll describe the "more complete" way, which works for all cases. The steps are:

1- In your CAD software, start with the tree volumes (both trunk + leaves);
2- The key point here is that you’ll have to create the enclosure in your CAD software. Create a simple enclosure, 100% solid. You shouldn’t use any boolean/subtract operation here. The enclosure and the trees should fully intersect with each other;
3- Bring this geometry to SimScale. As you have already created the flow region in your CAD software, you can proceed to create a simulation;
4- In the meshing operation, there’s a mandatory step. You need to declare the tree volumes as a “Cell zone”. For a standard mesh, creating a cell zone is pretty straight forward:

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If you’re planning to use a hex mesh, cell zones can be created with surface refinements:
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As a result, the entire enclosure will be meshed, and you’ll be able to assign porosity to your cell zones.

And that’s pretty much it. Let us know if you’re able to achieve it!

Cheers

1 Like
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Thank you very much, @Ricardopg, that worked perfectly!

I had to remove the trunks in the CAD program from the flow volume, since I intend those to be ‘solid’, but otherwise your instructions were on-point.

I had tried everything you mentioned except having the flow volume explicitly defined from the CAD stage.

Thanks again!

2 Likes
4

Oh yes, good point. The trunks can be subtracted from the flow region. Glad that you got it to work!