# Non-orthogonal correction in SimpleFOAM

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 May 28, 2010, 02:10 Non-orthogonal correction in SimpleFOAM #1 Member   Jinbiao Xiong Join Date: Oct 2009 Location: China/Japan Posts: 50 Rep Power: 8 I am using a non-orthogonal mesh in the calculation. I tried to put the nonorthogonal as 1 to add some correction. But when I read the code of simpleFoam. I can not understand what difference it can make. It seems the correction just solve the matrix one more time, with little change in the matrix. The change of the matrix is only from pEqn.setReference(pRefCell, pRefValue) So I cannot understand what is going on with the non-orthogonal correction. Can any one explain it? Thanks a lot. Best, __________________ Jinbiao

 May 28, 2010, 08:10 #2 Member   Cedric Van Holsbeke Join Date: Dec 2009 Location: Belgium Posts: 81 Rep Power: 8 Non-orthogonal correction is not recommended for steady-state solvers as it is not needed to have a converged solution every time-step. Just put it to 0 and set limiters in your fvSchemes file in order to handle a non-orthogonal mesh. songwukong, sharonyue and namsivag like this.

 May 29, 2010, 02:43 #3 Member   Jinbiao Xiong Join Date: Oct 2009 Location: China/Japan Posts: 50 Rep Power: 8 Hi Cedric, Thanks for your reply. Do you mean I only need to apply the correction in the laplacian terms. For example laplacian (phi, *) Gauss linear corrected Thanks a lot. Best, __________________ Jinbiao

 May 29, 2010, 03:20 #4 Member   Cedric Van Holsbeke Join Date: Dec 2009 Location: Belgium Posts: 81 Rep Power: 8 If your max orthogonality is < 60, you can indeed use "Gauss linear corrected" for your laplacian scheme, if higher you can use "Gauss linear limited 0.333". Your snGradScheme has to be edited accordingly (either corrected or limited 0.333). You can also limit the other schemes. For example: Code: ```gradSchemes { default cellLimited Gauss linear 1; } divSchemes { default none; div(phi,U) Gauss linearUpwind cellLimited Gauss linear 1; ... } laplacianSchemes { default Gauss linear limited 0.333; } snGradSchemes { default limited 0.333; }``` lakeat, kiddmax, fumiya and 5 others like this.

 May 30, 2010, 00:14 #5 Member   Jinbiao Xiong Join Date: Oct 2009 Location: China/Japan Posts: 50 Rep Power: 8 Thanks a lot, Cedric. In your example, you used gradSchemes { default cellLimited Gauss linear 1; } This is my first time to know there is a cellLimited scheme. I am curious about the difference between cellLimited and other limited schemes? If possible, could you also explain what is the function of the numbers following the limited scheme. Thanks again. Best, __________________ Jinbiao

August 26, 2014, 03:52
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Pratik Nanavati
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Quote:
 Originally Posted by JinBiao Thanks a lot, Cedric. In your example, you used gradSchemes { default cellLimited Gauss linear 1; } This is my first time to know there is a cellLimited scheme. I am curious about the difference between cellLimited and other limited schemes? If possible, could you also explain what is the function of the numbers following the limited scheme. Thanks again. Best,
Limited versions of any of these 3 base gradient schemes (Gauss, leastSquares and fourth) can be selected by preceding the discretisation scheme by cellLimited (or faceLimited),

e.g. a cell limited Gauss scheme,

for more details you can refer http://www.openfoam.org/docs/user/fvSchemes.php (4.4.3 Gradient schemes)

 June 27, 2015, 07:09 #7 New Member   Ali Kadar Join Date: Oct 2014 Location: Delft Posts: 25 Rep Power: 3 This very nice document illustrates a lot about the choice of schemes, under-relaxation, pre conditioners for OpenFOAM. Special treatment for non-orthogonal meshes. very well said "Who owns the mesh, owns the solution!!" http://www.dicat.unige.it/guerrero/o...sandtricks.pdf __________________ A good solution is one which does justice to the inner nature of the problem- Cornelius Lanczos in a letter to Albert Einstein on March 9, 1947

 March 18, 2016, 10:32 #8 Member   AdOo Join Date: Mar 2016 Location: Bordeaux Posts: 91 Rep Power: 2 Hi all, I can't find the document that FlowAlways has post. Has anybody still got this document ? thank you, Adrien

 March 21, 2016, 05:47 #9 Member   AdOo Join Date: Mar 2016 Location: Bordeaux Posts: 91 Rep Power: 2 Hi all, I've found one which was maybe the same posted before. Here is the one I've found : http://www.dicat.unige.it/guerrero/o...sandtricks.pdf If anyone has oneother, I would appreciate to have it also. Have a nice day, Adrien

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