[piroshki]

Hello all,

I am having trouble creating a mesh that works well for a profiled bulb with a pointy "tail".

I wonder if anyone has any pointers they could share.

I have tried with a tip that goes to zero thickness, and with small flat face as per the attached images. In all cases the tip ends up being rather ugly...

The resulting mesh also won't let me create layers, another problem, which I suspect may be related. I've attached two screenshots of my CAD model, one of the mesh generated by SHM, and also the entire directory should someone want to try their luck...

Thanks much,

Tom.

[NablaDyn]

Seems you are looking for a more precise mesh description that places points and edges exactly where you want them. Since your geometry is so simple, I'd recommend boundary-prescribing, hexahedral meshes instead of SnappyHexMesh or (other automatic unstructured stuff).

Did you give BlockMesh a shot? Or do you know MegaCads (it's freeware, has a GUI and offers elliptic smoothing)? I use that for OpenFOAM meshing.

Fittingly I recently built a mesh alike yours with MegaCads:

[linnemann]

Salome is great for this.

Make a 2D mesh from a bunch of 4 sided squares that are combined into a shell.

Revolve that mesh, export to unv, use "ideasUnvToFoam" to convert mesh.

Use "autoPatch 89 -overwrite" to split mesh by angle, open i Paraview and rename the boundaries accordingly.

[piroshki]

Thanks NablaDyn and Niels for your thoughts. Both your answers make perfect sense, and I'll give them both a try for this bulb shape.

My issue is that this is really a precursor to a future study in which I will attach this bulb to a spar (wing, keel - same idea) so doing a simple body of revolution mesh won't be an option.

I'll also be interested in what happens when I modify the angle of attack, so I am thinking the strict "tunnels" your approach produce will also make things hard...

MegaCads looks really promising in this regard - I've send them a note and hopefully will get to test out the software.

Cheers,

Tom.

[linnemann]

Hi

To get angle og attack you can just mesh the outside as a sphere and then you can make a stl file that covers the inlet part and use "surfaceToPatch" command to extract the boundary condition for the inlet.

This way you can rotate the 3D mesh and then afterwards assign the inlet BC based on the surface stl.

If you dont know how to get the surface stl you can use Paraview to select particular surface cells, triangulate them and then export as stl.

For the other case you need to look into other meshers.
I've had good results with cfmesh, but never tried it on such a pointy bulb.

[NablaDyn]

Fortunately, MegaCads doesn't constrain you to 2D mesh revolution. It offers 3D meshing natively and delivers grids of outstanding quality. It allows for mutli-blocking and of course you are free to parametrise your mesh extensively. It is therefore an easy task in MegaCads (given you have become somewhat familiar with it), for instance, to incline parts, regions or blocks of your mesh dynamically, whilst keeping other parts in fixed positions.