[JakeAC]

Hello everybody,

I am trying to simulate gas flow and heat transfer through a converging-diverging nozzle using chtMultiRegionSimpleFoam, and I am running into a problem with creating the cell sets for defining the regions.

As you can see from the screenshot of the converging section, there are three regions: ambient air on the outside of the nozzle (top blue section), the nozzle wall (middle white section), and the gas moving through the nozzle (bottom blue section); the bottom plane is a symmetry plane. I am currently using boxToCell to create the cell sets for the cell zones that are defining the three regions. This creates the problem of having the "stair steps" along the wall rather than a single, smooth line, so I have been trying to figure out a way to basically define the gas cell zone as the combination of a rectangular prism with two triangular prisms, one for the converging portion and one for the diverging portion.

I have tried using boxToCell with one of the sides of the box being the nozzle wall, but that appears to not do anything, and maybe that is because part of the box is overlapping with another. I have also looked through the topoSet cellSet sources, and none of the other sources seem like they will be able to help create a triangular prism cell set.

I've just been using blockMesh and the topoSetDict to create the mesh and create the cellSets, but would another software, such as Gmsh, Pointwise, or the like, be able to set and define the cell sets/zones more easily and/or without the use of the topoSetDict? Or is there a good way to create the smooth wall cell set with blockMesh and topoSetDict that I have been missing?

I've also attached the blockMesh and topoSet files.

Thanks everybody,
Jake

[fumiya]

Why don't you use snappyHexMesh?
It is time-consuming to generate boundary-fitted mesh with blockMesh.

Hope this helps,
Fumiya

P.S.
We've developed ennovaCFD, a commercial mesh generator with OpenFOAM setup GUI. You can easily generate CHT meshes with cellZones as shown in the attached picture.