[lebc]

Hi guys,

I'm starting to analyze wind turbines in OpenFoam and I'm having some trouble with snappyhexmesh...

What I'm trying to do is to generate a mesh to analyze only the rotor on a free flow (not considering terrain, towers, and other details, but using actuationDiskSource for the rotor representation...), so I'm creating a simple rectangular mesh in blockMesh and using snappyhexmesh to refine a cylindrical region, but it does not recognize the specified refinement region...

My starting point was the turbine siting tutorial, just removing the terrain.stl and adjusting the coordinates.

From the log file I noticed this message, but I don't know if this is the cause of the problem:

" Number of intersected edges : 0 "

Any clue about it?

Thank you!

[Laika]

Hi Luis,

indeed sHM doesn't mark any cells for refinement, despite your refinementRegion.
(I've seen this before; I guess sHM needs at least one refinementSurface to get into refinement.)
I played with your snappyHexMeshDict, and modified it like this:

   refinementSurfaces
    {
        windTurbine1 
        {
            level (4 4);
            faceZone windTurbine1;
            cellZone windTurbine1;
            cellZoneInside inside;
        }
    }

    resolveFeatureAngle 30;

    refinementRegions
    {
        /*windTurbine1
        {
            mode inside;
            levels ((6 6));
        }*/

    }

The result is shown in the attached image.

I hope this helps,
happy foaming,

Laika,
still orbiting

[EhsanMh]

Hi Luis,

Check the attachment. Geometry specified in refinementSurfaces will be cutted from the base geometry.

If you mean that the selected regions is not refined, just decrease the size of background mesh or increase size of searchableCylinder.

[lebc]

Hi Ehsan,

This is the point, the regions for refinement were not being refined.

I increased the blockmesh number of elements in one direction and decreased the level to 4, and it worked! (actually only the blockmesh change was enough to make it work)

Do you know if there is any relation between the blockmesh and the ability of snappyhexmesh to refine some specific region?

Thank you for the reply!!

[EhsanMh]

I realized that the size of grid is greater than the size of your cylinder. I guess that it was not crossing any of edges, so snappy could not find any region. It selects edges which coincide with specified geometry, which in your case, as you mentioned in first post, was zero.

[Laika]

Hi Ehsan and Luis,

Playing around a bit and sharing some experiences...
Luis used a refinementRegion.
Both Ehsan and myself suggested to use a refinementSurface.

The refinementRegion yields a nicely refined mesh in the desired disk-shaped region, if the background mesh is finer.
The refinementRegion yields a nicely refined mesh (but near the disk-region's surface only; not uniformly in the entire disk volume), even on Luis's original backgroundmesh.

Attached is an impression of the result of my test using Luis's original background mesh, colored by domain. (splitted using splitMeshRegion)

cheers,
Laika,
still orbiting

[lebc]

Hi Ehsan and Laika,

I think I got the ideia!!! I'm new to OpenFoam (about 2 months), so it will take me some time to fully understand how it works.

Laika,

After posting the doubt I refined the background mesh and I could see the results you said.

Thank you guys for helping!!! I'll be back soon!!