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Flow around airfoil using WALE LES model, why Cp and Cf are not correct? |
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February 12, 2020, 18:57 |
Flow around airfoil using WALE LES model, why Cp and Cf are not correct?
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#1 |
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navid toussi
Join Date: Nov 2015
Posts: 20
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Hi everyone! I was running a case of flow passing an airfoil at Reynolds 60000 using WALE LES model in OpenFoam and after checking the Pressure and Skin friction coefficients,I noticed that the results are very different that the previous studies, and I don't know what could be the source of problem.
For this reason, I am gonna share all my settings here with you hopefully someone can tell me what was my mistake! The mesh I was using is very dense around the airfoil that I have y+<1 , so I haven't used any wall function. Also I used Code:
FoamFile { version 2.0; format binary; class volVectorField; location ""; object U; } /*---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------*/ dimensions [0 1 -1 0 0 0 0]; internalField uniform (0.970295726 0.2419218955 0.); boundaryField { in { type fixedValue; value uniform (0.970295726 0.2419218955 0.); } out { type zeroGradient; } wallup { type fixedValue; value uniform (0. 0. 0.); } walldown { type fixedValue; value uniform (0. 0. 0.); } front { type cyclic; } back { type cyclic; } } Code:
FoamFile { version 2.0; format binary; class volScalarField; location ""; object p; } /*---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------*/ dimensions [0 2 -2 0 0 0 0]; internalField uniform 0.; boundaryField { front { type cyclic; } in { type zeroGradient; } out { type fixedValue; value uniform 0.; } wallup { type zeroGradient; } walldown { type zeroGradient; } back { type cyclic; } } Code:
FoamFile { version 2.0; format ascii; class volScalarField; location "0"; object nut; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -1 0 0 0 0]; internalField uniform 0; boundaryField { in { type zeroGradient; } out { type zeroGradient; } wallup { type zeroGradient; } walldown { type zeroGradient; } front { type cyclic; } back { type cyclic; } } Code:
FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default backward; } gradSchemes { default Gauss linear; grad(U) Gauss linear; } divSchemes { default none; div(phi,U) Gauss linearUpwind grad(U); div(phi,k) Gauss limitedLinear 1; div(phi,B) Gauss limitedLinear 1; div(phi,nuTilda) Gauss limitedLinear 1; div(B) Gauss linear; div((nuEff*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default corrected; } Code:
FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { p { solver PCG; preconditioner DIC; tolerance 1e-7; relTol 0.01; } pFinal { solver PCG; preconditioner DIC; tolerance 1e-08; relTol 0; } "(U|k|nuTilda)" { solver smoothSolver; smoother GaussSeidel; tolerance 1e-05; relTol 0; } } PISO { nCorrectors 2; nNonOrthogonalCorrectors 0; } Code:
FoamFile { version 2.0; format ascii; class dictionary; location "constant"; object turbulenceProperties; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // simulationType LES; LES { LESModel WALE; turbulence on; printCoeffs on; delta cubeRootVol; WALECoeffs { Cw 0.5; } cubeRootVolCoeffs { deltaCoeff 1; } } I really appreciate any help and advice |
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February 12, 2020, 19:08 |
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#2 |
Senior Member
Herpes Free Engineer
Join Date: Sep 2019
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Can you share also the mesh and the benchmark data?
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February 13, 2020, 06:37 |
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#3 |
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navid toussi
Join Date: Nov 2015
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Hi and thanks for reply. Below you can find some photos of my mesh:
my mesh is having almost 30 mil number of cells and is fully unstructured mesh. In third dimension it has 48 layers. As i mentioned before, the minimum size of the cell around the wall is small enough to have y+<1. a.png b.jpg c.jpg d.jpg e.jpg |
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February 13, 2020, 17:19 |
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#4 |
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Herpes Free Engineer
Join Date: Sep 2019
Location: The Home Under The Ground with the Lost Boys
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It is still difficult to follow the question. We dont know what and to which extent you have the differences between the benchmark and the simulation, for example. We dont know how you did postprocess the simulation outcome. etc etc etc
I am just giving examples, rather than trying to know these.
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The OpenFOAM community is the biggest contributor to OpenFOAM: User guide/Wiki-1/Wiki-2/Code guide/Code Wiki/Journal Nilsson/Guerrero/Holzinger/Holzmann/Nagy/Santos/Nozaki/Jasak/Primer Governance Bugs/Features: OpenFOAM (ESI-OpenCFD-Trademark) Bugs/Features: FOAM-Extend (Wikki-FSB) Bugs: OpenFOAM.org How to create a MWE New: Forkable OpenFOAM mirror |
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February 16, 2020, 13:55 |
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#5 |
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Santiago Lopez Castano
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The first thing I would suggest you is to make a structured grid, with the appropriate boundary layer resolution near the wall (at least 7 points within the viscous layer). the geometry is too trivial, and using triangular meshes may reduce the order of approximation of the interpolation of gradients and the calculation of gradients themselves. If you insist on the road of triangular meshes, make at least sure you are using leasSquares schemes for the calculation of gradients. One additional thing: stabilizing the solution via blending (linearUpwind) breaks the conservation property of the advection term. This means you're "losing" energy....
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February 16, 2020, 23:55 |
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#6 | |
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navid toussi
Join Date: Nov 2015
Posts: 20
Rep Power: 10 |
Quote:
Another question is which schemes exactly are you suggesting if I end up using triangular mesh ? Thank you again for your help |
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