[RjwV]

Hello everyone,

I've been trying to insert multiple cylinders in my mesh by using the snappyHexMesh tool. Also, I would like to refine the grid around these cylinders. The cylinders can easily be added via searchableCylinder, the refinment can easily be done via castellatedMeshControls - refinementSurfaces - inserted_cylinder_name - level {...}. So far so good.

However, I would like to have a 2D simulation where the column is one cell deep, so I would like to refine the grid ONLY in the x and y directions, not in the z direction. As shown in this picture, the grid has refined in the z direction (depth).

First question; is refinement in two directions instead of three possible via snappyHexMesh?

Furthermore, I have tried using extrudeMesh to extrude the mesh into a one layered (i.e. 2D) mesh by extruding exposedPatchName "cyl01", which results in what I wanted w.r.t. the number of cells in depth. Also, this results in the cylinder being 'attached' to the front patch (see picture). This is something I do not want. Furthermore, I have noticed that implementing a boundary condition for the inlet can under specific circumstances cause problems; e.g. one side of the inlet patch has no velocity and the other has the given velocity in the input file.

So my second question; is there any better way to create a 2D mesh for my case, or are there any better extrudeMesh or perhaps even snappyHexMesh settings to achieve this?

I am using the twoPhaseEulerFoam solver btw. The case has been attached. Case can be replicated by using the "blockMesh", "snappyHexMesh -overwrite" and "extrudeMesh" commands, in that order. If anymore information is required I will try to supply it. Hope you guys can give me some ideas in which direction to go after this. Thank you in advance.

Kind regards,
Ramon

[nucat]

Hey,

you can use extrudeMesh (maybe with combination of createPatch) after generating refined Mesh, so you get 2D refined Mesh.

That document describes how to setup such kind of 2D case with snappyHexMesh:
http://upcommons.upc.edu/pfc/bitstre...9/1/memory.pdf

Greeting,
Nucat

[RjwV]

Thank you nucat. I managed to avoid getting the same problem this way.

I did a similar procedure, blockMesh, snappyHexMesh -overwrite, extrudeMesh (in that order). My mistake was in extrudeMesh:

My settings extrudeMesh (resulting in the merging of "front" and "cyl01":
sourcePatches (back);
exposedPatchName "cyl01";

The settings to avoid this merging behavior:
sourcePatches (front);
exposedPatchName back;

Quite a simple mistake, but a very clear and good solution. Thanks again!

Kind regards,
Ramon

[Ruli]

Dear Ramon,

if you mesh "only" cylinders (which means relatively simple, structured geometries), why do you not use blockMesh for meshing. Gives you much better control of mesh quality...

Best regards
Julian

[RjwV]

I have though about it, and two things have stopped me from doing this;

- The number of cylinders I want to add can reach up to about 50, to me it seems this will create complex and difficult to see understand blockMesh files (correct me if this is not the case, I have not used blockMesh yet to simulate large number of cylinders).

- I have not yet set-up a lot of non rectangular blockMesh meshes, I know it is possible to create round objects via arcs and such, but I do not fully understand it still.

I also heard that m4 could be a good option to add cylinders via blockMesh, however again the question arises whether this is more convenient when adding a large number of cylinders.

Any further thoughts on this?

Kind regards,
Ramon