[BrownieBytes]

Hey all,

TL;DR - I need to make regions out of an STL with a cavity, how can I do that? Please provide tutorials, videos, or advice.

I am trying to find the correct workflow and utilities to model my system correctly. It pulls together a lot of concepts, so please feel free to share any advice you may have. For context, this is for a research project using the nuclear reactor modeling code SERPENT to model the behavior of a nuclear reactor core. The end goal is that OpenFOAM takes care of the density and temperature of the core materials and SERPENT then interprets that data to output the power density at each point. So, if anyone has advice for external couplings, please share.

The current challenge is that I want to use a single STL file to split up my regions. For the sake of simplicity, imagine that the STL is of a closed aluminum can. There are two closed surfaces on this can that create the boundaries between three regions: fluid inside the can, the material that makes up the can, and fluid outside the can. From what I could gather, I need to create a blockMesh, use topoSet to extract the three regions from the STL, use snappyHexMesh to prepare the mesh, and then refine further if wanted. Here is a great opportunity to tell me I am way off and ought to use a different procedure.

When I use surfaceCheck on the STL, it quickly and accurately identifies that the STL is both closed and that it has two parts. It then creates OBJ files for each of the two surfaces if anyone has advice on how I might just use those. It is my understanding that snappyHexMesh will throw away the interior volume if I don't preprocess the model, so how can I use topoSet to achieve a similar effect to surfaceCheck? I would rather not create two separate STLs because all of the relevant information is in the first one. Also, in the format that SolidWorks produces STLs, there is only one region in the STL file, so I can't split the mesh volume using literal STL regions. The three regions would be (blockMesh - externalSTL), (externalSTL - internalSTL), and (internalSTL). So, what tool (if not topoSet) can I use to automatically split the STL into inside and outside and define these regions?

Once this is done, I would like to use the chtMultiRegionSimpleFoam solver to figure out the steady state solution for temperature distribution. Nuclear reactors have a small feedback loop on their operation where essentially power production is temperature dependent. To account for this, I am planning on using the externalCoupledHeater tutorial as a starting point.

I can attach files if that would be helpful, but something tells me that it wouldn't accomplish much if I did. Let me know if you want them though.

Thanks,
BrownieBytes

[Yann]

Hello,

What OpenFOAM version are you using?

Yann

[BrownieBytes]

Originally Posted by Yann

Hello,

What OpenFOAM version are you using?

Yann

Hey Yann,

Looks like it's version 2206.

I was able to get my snappyHexMesh to half work (It somewhat accurately determined the external fluid region), but how do I get the other two regions to appear?

[Yann]

Hello BrownieBytes,

For multi region simulations, you can define multiple regions in snappyHexMeshDict thanks to the locationsInMesh (rather than using the usual locationInMesh)

See documentation here: https://doc.openfoam.com/2306/tools/...ocationsInMesh
And an example in the snappyMultiRegionHeater tutorial: https://develop.openfoam.com/Develop...tiRegionHeater

Regards,
Yann