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About the non-orthogonal mesh and non-orthogonal corrector |
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January 26, 2013, 09:23 |
About the non-orthogonal mesh and non-orthogonal corrector
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#1 |
Member
jack
Join Date: Jul 2011
Posts: 52
Rep Power: 14 |
Hello everyone
I used a modified solver to simulate a circular pipe flow.The mesh is non-orthogonal.So I think I need use non-orthogonal corrector in the fvSchemes. But the results is not good as the time developing.It seems that the mesh have great influence to the velocity.I have attached my velocity contours and mesh here.I hope you can help me to analysis the the fvSchemes I used. I think the problem maybe lie in the non-orthogonal corrector,but I don't have enough experience.I set the fvSchemes as following: Code:
ddtSchemes { default Euler; } gradSchemes { default cellLimited leastSquares 1; // grad(p) Gauss linear; } divSchemes { default none; div(phi,U) Gauss linearUpwindV cellMDLimited leastSquares 1.0; div(phi) Gauss linear 1; div(phiB,Dsig) Gauss linear 1; } laplacianSchemes { default Gauss linear corrected; laplacian(nu,U) Gauss linear corrected; laplacian((1|A(U)),p) Gauss linear corrected; laplacian(DT,T) Gauss linear corrected; } interpolationSchemes { default linear; interpolate(HbyA) linear; } snGradSchemes { default corrected; } fluxRequired { default no; p; } regards! lg88 |
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January 27, 2013, 06:15 |
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#2 |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
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Hi lg88,
What do you have in "system/fvSolution"? I'm asking this because the number of correctors is defined on that file: http://www.openfoam.org/docs/user/fvSolution.php Best regards, Bruno
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January 27, 2013, 08:53 |
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#3 |
Member
jack
Join Date: Jul 2011
Posts: 52
Rep Power: 14 |
Thank you for your reply.I set my fvSolution as following:
Code:
solvers { p { solver PCG; preconditioner DIC; tolerance 1e-06; relTol 0; }; pFinal { solver PCG; preconditioner DIC; tolerance 1e-06; relTol 0; }; ephi { solver PCG; preconditioner DIC; tolerance 1e-06; relTol 0; }; U { solver PBiCG; preconditioner DILU; tolerance 1e-05; relTol 0; }; } PISO { nCorrectors 3; nNonOrthogonalCorrectors 3; pRefCell 0; pRefValue 0; } // ************************************************************************* // Best regards! lg88 |
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January 27, 2013, 15:15 |
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#4 |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,975
Blog Entries: 45
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Hi lg88,
I'm not experienced enough on this, but I suggest that you also provide the following details, so that someone with more experience can help you during this week:
Bruno
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January 28, 2013, 06:51 |
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#5 |
Member
jack
Join Date: Jul 2011
Posts: 52
Rep Power: 14 |
Hi Bruno
I run the command Code:
checkMesh Code:
Checking geometry... This is a 3-D mesh Overall domain bounding box (-1 -1 0) (1 1 0.02) Mesh (non-empty, non-wedge) directions (1 1 1) Mesh (non-empty) directions (1 1 1) Mesh (non-empty, non-wedge) dimensions 3 Boundary openness (4.2856998285e-20 5.9259059357e-20 -2.7446997359e-19) Threshold = 1e-06 OK. Max cell openness = 3.9590866047e-16 OK. Max aspect ratio = 159.52539546 OK. Minumum face area = 1.5253865084e-06. Maximum face area = 0.0014060260459. Face area magnitudes OK. Min volume = 1.061859197e-07. Max volume = 2.8120520918e-05. Total volume = 0.062779645967. Cell volumes OK. Mesh non-orthogonality Max: 88.365490847 average: 7.2145668686 Threshold = 70 *Number of severely non-orthogonal faces: 32. Non-orthogonality check OK. Writing 32 non-orthogonal faces to set nonOrthoFaces Face pyramids OK. Max skewness = 0.81894169959 OK. Mesh OK I modified my solver according icoFoam. The fluid in my case is not a real material.I set its density to 1,kinematic viscosity 0.001,velocity 1 and Reynolds number 1000. Then I modified the laplacianSchemes from Code:
{ default Gauss linear corrected; laplacian(nu,U) Gauss linear corrected; laplacian((1|A(U)),p) Gauss linear corrected; laplacian(DT,T) Gauss linear corrected; } Code:
{ default Gauss linear limited 0.5//or 0.333; laplacian(nu,U) Gauss linear limited 0.5//or 0.333; laplacian((1|A(U)),p) Gauss linear limited 0.5//or 0.333; laplacian(DT,T) Gauss linear limited 0.5//or 0.333; } I have no ideal about it. Thanks for your advice. regards! lg88 |
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January 29, 2013, 02:53 |
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#6 |
Member
jack
Join Date: Jul 2011
Posts: 52
Rep Power: 14 |
Hello everyone
When I set the laplacianSchemes from: Code:
{ default Gauss linear corrected; laplacian(nu,U) Gauss linear corrected; laplacian((1|A(U)),p) Gauss linear corrected; laplacian(DT,T) Gauss linear corrected; } Code:
{ default Gauss linear limited 0.5//or 0.333; laplacian(nu,U) Gauss linear limited 0.5//or 0.333; laplacian((1|A(U)),p) Gauss linear limited 0.5//or 0.333; laplacian(DT,T) Gauss linear limited 0.5//or 0.333; } regards! lg88 |
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March 4, 2013, 10:56 |
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#7 |
Senior Member
HECKMANN Frédéric
Join Date: Jul 2010
Posts: 249
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In my point of view your skewness looks a bit high (0.8). I had a similar problem that I solved by introducing a skewcorrector. You can look at my scheme here http://www.cfd-online.com/Forums/ope...om-solver.html
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March 5, 2013, 03:04 |
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#8 |
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Sorry for the stupid question but I am curious:
If it is a simple, straight pipe, why do you not have a square block in the middle? Why are its edges curved in this manner? Maybe changing this may improve your mesh properties and therefore correct your solution. |
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March 5, 2013, 03:11 |
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#9 |
Senior Member
HECKMANN Frédéric
Join Date: Jul 2010
Posts: 249
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I guess he used a "smoothing" function from his grid generator. Sometimes I get the same kind of restults with Pointwise.
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