FSI - two Boundary Layers

[Sara Zambon]

Hi everyone,

I'm wondering if it's possible to mesh the fluid domain in an FSI mesh with a boundary layer, after creating the solid wall (using Boundary layer as an extrusion method in the first place) - see "img1.png"

I'll explain myself better:
1) create the solid mesh by extruding outward the surface of your choice (at the same time the fluid one will be created)
2) export the two entities as two separate domains
3) import the "walls_combined.vtp" or "walls_combined_connected_region_0.vtp" file (in the Domain_1 folder and Domain_2 folder respectively) as a new model,
4) close the caps and remeshing them with the same size used for the initial mesh
5) mesh the model from step 3 with a boundary layer (inward from wall); without surface meshing (only Volume meshing, as suggested here - https://simvascular.github.io/docssvFSI ... fluid_mesh )

I tried to do the steps backwards, thus creating the fluid domain first (with an inward B.Layer) and then the extruded wall, but the SV window always closes unexpectedly as I press "Run Mesher" in the last phase. I even tried to skip the "remeshing caps" step, as I thought it could be caused by the restriction of the previously created surface mesh. I managed to quickly screenshot the terminal outputs before they closed (see attachments).

My demo Project: https://drive.google.com/drive/folders/ ... sp=sharing

Thank you!

[David Parker]

Hi Sara,

Importing a mesh as a model is perilous, not clear how to make sure meshes share nodes, that face IDs are correct, etc.

I think the best way to do what you want is to use VTK to remove the fluid region from the solid and then merge the solid and fluid meshes. You can use the VTK vtkThreshold() and vtkAppendFilter() functions to do this.

Having said all this I am wondering how do you plan on getting the fluid and solid nodes to match at their interface? The solid and fluid meshes are using different mesh generation methods so the nodal coordinates will not necessarily match.

Cheers,
Dave

[Sara Zambon]

Thank you David!

Sorry for the delay,
Exactly, that's why i was triying to import the mesh as a new model! As suggested here (https://simvascular.github.io/docssvFSI ... fluid_mesh) if you import the ".vtp" file extracted from the solid mesh and use it to generate the new volume mesh (of the fluid domain), you can then run an FSI simulation. Obviously, you have to deselect the "surface meshing" option before starting the mesher, as you already have it from the beginning. I was infact able to follow that tutorial in the abovementioned link and all went well (without setting a boundary layer in the fluid domain, though).
I thought that was a method to be sure to have matching nodes at he interface.

But maybe, as you said, importing a mesh as a model is a dangerous path anyways.

Thank you again,
Sara

[David Parker]

Hi Sara,

Now I understand, turning off the Surface mesh option should keep the interface nodes consistent. Let me go through the tutorial you referenced and see what I get, there might be a bug in the SV mesh code.

Cheers,
Dave

[Sara Zambon]

All right! Thank you David