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Old   December 30, 2011, 16:56
Default Trimmer Troubles
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Darryl McClure
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I am trying to generate a mesh to run with k epsilon, high y+ model. The geometry is a channel that resembles an 'H'. I am modelling only 1/4 of the channel since the geometry has two symmetry planes. The mesh I have is attached. The bottom most and left most boundaries are symmetry planes while the other four are wall boundaries.

My goal is to generate a structured grid of hexahedral cells using the trimmer. I am having trouble ensuring that the trimmer places my chosen base cell size at the wall boundaries. You will see in the picture that the cells adjacent to the top boundary are much smaller than the others. Since I want to use high y+ model, the near wall cell centroid's need to be at ~y+ = 30, I need to control the thickness of the wall layer.

I have aligned the mesh, and the origin of the coordinate system is at the bottom right corner of the mesh. I have also tried using the prism layer because of the control it gives in the near wall region, but since my geometry is well suited to hexahedral cells, I wanted to pursue a mesh generated with the trimmer only.

So my question would be, is there any way to control the trimmer's generation of the wall layer?

Any help would be great.
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Old   January 2, 2012, 20:05
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The trimmer is not the right model to create any mesh with control over the near-wall layers. No matter what you might like to do, the trimmer is intended to create a bulk mesh in complex domains, not to give control of the near-wall mesh to the user to mesh a nice-looking geometrie just because somebody doesn't like the prism layer mesher. You might do this somehow with the trimmer, but the intended model for this is the prism layer mesher. All you can try to use with the trimmer is the surface size and the growth ratio, but anyway, this is not the recommended way and you don't have any control of the mesh size in wall normal direction other than the number of layers with the same cell size before it will double the cell size.
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