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Cell Skewness Affect Divergence?

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Old   May 23, 2013, 23:40
Default Cell Skewness Affect Divergence?
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I used two types of meshing: tetrahedrons and cutcell. I run both under the exact same conditions.
The only difference is the type of mesh (tetraheral vs. cutcell) and the # of elements for each type of mesh and the quality (inherent problems of the type of mesh used).
My solution always diverges when I use the cutcell mesh. I always receive the "temperature is limited to...." during iterations. When I do a case check with the cutcell mesh, i receive the warning that the cell skewness is over the recommended 0.98. I do not receive this warning when I use the tetrahedral mesh.

Is cell skewness really that important? Important enough to cause divergence, particularly in the energy residual?
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Old   May 24, 2013, 04:49
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It is very important indeed. Try to refine your mesh or lower the underrelaxation factors and perform more iterations on the pressure correction.
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Old   May 24, 2013, 16:09
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Quote:
Originally Posted by Aeronautics El. K. View Post
It is very important indeed. Try to refine your mesh or lower the underrelaxation factors and perform more iterations on the pressure correction.
Thanks for the reply! What do you mean by "pressure correct?" I am new to ANSYS, so I am not familiar with some of the terms.
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Old   May 26, 2013, 11:36
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Pressure Correction has to do with the numerical solution of the problem not with ansys in particular. I suggest that you should study a few things about the SIMPLE method (which you probably use in ansys) before proceeding with your problem.
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Old   May 27, 2013, 03:10
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Cell skewness is very important specially when you are working in 3D. I don't know about your case but in 3D, if the cell skewness is above 0.9, then negative volumes are created.
Try to reduce this factor when you are meshing.

Best of luck!
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