How to brick mesh pipe for CFD?

[td 2]

Hi,

 

I'm trying to brick mesh a straight pipe for OpenFOAM CFD, meaning I need a boundary layer, shell elements on the outer surfaces and a core - all hex elements. My meshing attempts up to now were only partially successful. I created a boundary layer by splitting the solid in an inner and outer pipe, then subtract one from the other, deleting the solid so I've got the inner and outer surfaces, created a surface mesh, then brick elements by using Element offset for the boundary layer. Unfortunately, the shell elements are lost in the process and I don't quite know how to create shells from the existing solids. Project nodes does not seem to be the right tool.

 

If someone could post a general workflow for this type of brick meshing I'd be very grateful. I've only used CFD tetramesh up to now, but OpenFOAM does seem to prefer brick elements. Unfortunately, I can't use hex core with a tetra oder penta boundary layer and transition, OpenFOAM can't handle different element types at once.

 

Edit: Sorry, this should have been posted in the Hypermesh subforum!

[Q.Nguyen-Dai 293]

Some pictures? Share model HM?

[td 2]

I just noticed that the shell mesh I use for the element offset is preserved, so my previous post is partially wrong. I used the outer circumference as source meshing surface, thus it's the only surface containing shell elements. Now I need to create a matching surface mesh on the remaining inflow/outflow surface and ensure connectivity between everything.

 

The pipe is 0.5m in length and 0.1m in diameter.

hexpipe.hm

[Q.Nguyen-Dai 293]

Use "solid map" meshing with splitted solid like screenshot:

[td 2]

Thank you, looks promising. But that does not resolve the issue of the surface mesh, unfortunately. How can I get a matching mesh on every outer surface from the solid mesh or vice-versa? OpenFOAM needs those to define the boundary conditions.

[Q.Nguyen-Dai 293]

Go for solid mesh firstly. When you have good solid mesh, surface mesh will be extracted easily by using "Tool" => "faces".

[td 2]

Huh, that was a lot easier than I thought. Thanks a lot!

[td 2]

Hi again,

 

I've got another question concerning biasing towards the middle axis of the pipe. The elements always begin to skew as can be seen in the image. How can I avoid this?

[Q.Nguyen-Dai 293]

If you want more control on this surface, try to split it into 3 zones as following picture:

 

[td 2]

Wonderful, I managed to get a good mesh with this method! Thanks again. I'll remember that in the future.