snappyHexMesh refinement
 

Dear snappyHexMesh users,

I've been playing with snappy for a few days and I am wondering something. Is it beter to start snappy with a very fine mesh as a base ans only do 1 or 2 level of refinement around my surface, or to start with a coarse mesh and then impose 6or 8 level of refinement in the snappyHexMeshDict?

To give an example, let say we have a mesh at level 1 in blockMesh, the two options are:
- use this mesh and chose a uniform refinement of 4 around the surface in snappy.
- refine blockMesh mesh by 4 in each direction and then use snappy without refinement, or with a refinement level of 1.

Not easy to explain, but i hope you'll understand.
If somebody have an idea, that would be nice.

Regards,

Vincent

refinement ratio
 

Hi Vincent,

the only important thing is the maximum and minimum size of our cells.

When you want to set a refinement with a ratio of 1:8 towards the surface, and the cell size at the surface schould be, lets say 2mm, the initial cell size would be 16mm and the surfaceRefinement-level in sappy would be then 3. (2³=8)

Since very small cells make your solution slower and more unstable, and a too coarse mesh delivers not enough information, this is a important point to think about.

If you are starting with a very coarse mesh from blockMesh, snappy would need perhaps more time for the refinement iterations. But I'm not shure - perhaps you could do some experiments and post the results here.