Skewness is defined as the difference between the shape of the cell and the shape of an equilateral cell of equivalent volume. Highly skewed cells can decrease accuracy and destabilize the solution. For example, optimal quadrilateral meshes will have vertex angles close to 90 degrees, while triangular meshes should preferably have angles of close to 60 degrees and have all angles less than 90 degrees. A general rule is that the maximum skewness for a triangular/tetrahedral mesh in most flows should be kept below 0.95, with an average value that is less than 0.33. A maximum value above 0.95 may lead to convergence difficulties and may require changing the solver controls, such as reducing under-relaxation factors and/or switching to the pressure-based coupled solver.
Dear Wahidullah Hakim Safi ,
I understand your problem exhibits during calculations. I am afraid there is no simple remedy to your problem. I think the best solution is to follow those simple three steps:
I hope that helps.
Kind regards,
Dr A. Szymański
Hello
First of all, you have to work on your mesh to increase mesh quality before import it in OpenFOAM if you are using an external CFD mesher. This is the best solution.
Secondly, the definition of skewness in OpenFOAM is quite different from the general definition that you mentioned. This is why sometimes checkMesh utility shows skewness bigger than 1. Thus, the value less than 4 would be acceptable by OpenFOAM. For more details and information please refer to Hrvoje Jasak PhD thesis entitled:
"Error Analysis and Estimation for the Finite Volume Method with Applications to Fluid Flows "
To decrease the mesh skewness, you can use SnappyHexMeshDict to control it.
Alternatively, you can use mesh tools to generate a good mesh and import it into OpenFOAM
Luofeng Huang Could give more details on using SnappyHexMeshDict to control the skewness?
Artur Szymański By simplying the geometry, do you mean using right angle will be better than chamber of fillet on the geometry?
Thank you both
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