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[GAMBIT] Fixing a poor quality mesh

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Old   April 21, 2009, 10:50
Question Fixing a poor quality mesh
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In a portion of my geometry, I have a volume that is not meshing very well. I am able to generate and "o-grid" (Blue mesh in the pictures) easily with the hex/map volume mesh. I want to use prismatic cells to fill the rest of the domain (the red mesh) using the cooper scheme. I have been somewhat successful getting this to work. Right now, the red mesh has a an equiskew size of 0.91. If I change the edge meshing straight piece of the source face even a little, this number goes up and sometimes I even get inverted cells. What is the best way to reduce my equiskew size for this type of mesh? Thanks in advance.



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Old   April 21, 2009, 13:58
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Why don't you try to fill it wit tet-hexcore?
Gambit will generate the outer layer with tetra and prism and the core with hexa.
If you still want prism, then I would suggest splitting the volume along its axis (y).
The problem here, is that Gambit has to project an half disk onto an half "rectangle".
You can help gambit, if the projection is generated in more than one step
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Old   July 15, 2010, 18:45
Default in order to have a better quality of your mesh
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Hi man, I got a problem like yours, and then I started to think to divide my domain in several blocks. At the end of the day I achieved a good results by generating several blocks and the mesh is structured everywhere. First of all try to create the central part of your mesh at squared base instead of circular.
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Old   December 15, 2010, 12:48
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What do you mean with inverted cells? I have a problem when doing the Grid in Fluent that says I have inverted elements and non-positive volumes. I'm trying to mesh an airfoil.
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Old   December 16, 2010, 10:44
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Go to examine Mesh and check where are those cells (choose Volume in quality type and set lower and upper limit for displaying only negative cells).
Most of time, you will understand the problem as you see where are bad cells
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Old   December 18, 2010, 13:44
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Forrest, if this is some of a circular-to-rectangular transition duct, then it might be worth while for you to look at a Pointwise/Gridgen tutorial example, where creating a grid for the same geometry has been shown very clearly.
I struggled with very poor quality meshes for a transition duct as well (it is for my masters thesis). Why don't you use a 'Pave' hex unstructured mesh in the interior instead of a tet mesh? I did find it that it helps in reducing the skewness.
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