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Gambit - meshing over airfoil wrapping (?) problem

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Old   July 7, 2011, 11:00
Default Gambit - meshing over airfoil wrapping (?) problem
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I'm having a problem in Gambit with the mesh over an airfoil.

For most of the domain the mesh is exactly like I wanted but in a zone somewhat between the trailing edge and the maximum thickness point of the upper part of the airfoil it is causing problems.

I exported the airfoil shape from Solidworks (it is a 3d model, but the problem here is with one of the slices of that model, so this is a plane mesh like bidimensional examples).

Here is the model before the volume (and naturally face) meshing. As you can see it's a C mesh with 2 zones (=volumes) over the airfoil, one for upper and another for lower flow.

Here is the general mesh view after the volumes being meshed. It creates negative volume elements because of the problem shown in the images below.

From this scale we can start noticing the problem

And comparing both the upper and lower meshes on a closer scale it is becoming more obvious

The lower part is an example of how it should be

And this is the problem. I don't know what it does, it seems to wrap the mesh itself and it does not respect the meshing scheme in the "j" direction, where it should have more elements closer to the wall.

I use the hex-map instruction to mesh the volume (and so also the "bidemensional" faces). It seems to be close to correct as the mesh nodes on the airfoil and the lines that come from the farfield are consistent, but in this zone there is obviously some problem.

When I use less elements on the vertical, "j", direction, the volumes and the meshing have no errors BUT as in this example the elements that were supposed to be in greater number near the wall are not, they gather together a little over it, but as they are in less number than in this example they don't end up wrapping themselves and the mesh is possible to be made, although it also violates the meshing scheme.

With your experience, is this a meshing scheme problem (maybe the mesh algoritm doesn't like the airfoil shape? In this case I suppose splitting the upper face into more zones would solve the problem) or do you think it is a geometrical problem (I had some of those but here it seems to be correct everywhere else)? Any ideas on how to solve it?

Many thanks!
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Old   July 11, 2011, 05:59
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Maxime Perelli
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Try to split your volumes around the airfoil (with an ellipse or whatever).
And remesh the new volumes
In memory of my friend Hervé: CFD engineer & freerider
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