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Boundary conditions K-Omega SST. Air Knife Simulation |
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December 31, 2019, 04:18 |
Boundary conditions K-Omega SST. Air Knife Simulation
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New Member
Gustavo Barahona
Join Date: Dec 2019
Location: Germany
Posts: 2
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Hi everybody!
I'm analyzing several geometries for the construction of an Air Knife. I don't have much experience working with OpenFoam and my solution is not converging. The speeds I am getting are extremely high (see attached image). After reading several Threads I realized that the error may be in the bcs. In the actual application the total pressure at the inlet is about 300mbar. For p, U, k, w and nut files I used then this settings: p File internalField uniform 0; boundaryField { fixedWalls { type zeroGradient; } //inlet // { // type zeroGradient; // } inlet { type totalPressure; p0 uniform 3E4; gamma 0.0; value $internalField; } outlet { type fixedValue; value uniform 0; } } U File boundaryField { fixedWalls { type noSlip; } inlet { type pressureInletVelocity; value $internalField; } outlet { type zeroGradient; } } k File internalField uniform 2.34; boundaryField { fixedWalls { type kqRWallFunction; value uniform 0; } inlet { type turbulentIntensityKineticEnergyInlet; intensity 0.05; value $internalField; } outlet { type inletOutlet; inletValue $internalField; value $internalField; } } omega File internalField uniform 50; boundaryField { inlet { type fixedValue; value $internalField; } outlet { type inletOutlet; inletValue $internalField; value $internalField; } fixedWalls { type omegaWallFunction; value $internalField; } } nut File internalField uniform 0; boundaryField { inlet { type calculated; value uniform 0; } outlet { type calculated; value uniform 0; } fixedWalls { type nutkWallFunction; value uniform 0; } } From a previous simulation on a similar air knife, I calculated the k-value. In that simulation the value of the velocity in the area of the Inlet was about 25 m/s. In a second simulation I tried to use this initial condition, but the simulation was always not converging. p File internalField uniform 0; boundaryField { fixedWalls { type zeroGradient; } inlet { type zeroGradient; } outlet { type fixedValue; value uniform 0; } } U File internalField uniform (0 0 0); boundaryField { fixedWalls { type noSlip; } inlet { type fixedValue; value uniform (25 0 0); } outlet { type zeroGradient; } } My fvSchemes and fvSolutions: solvers { p { solver GAMG; smoother GaussSeidel; tolerance 1e-7; relTol 0.01; } Phi { $p; } U { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.1; nSweeps 1; } k { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.1; nSweeps 1; } omega { solver smoothSolver; smoother GaussSeidel; tolerance 1e-8; relTol 0.1; nSweeps 1; } } SIMPLE { nNonOrthogonalCorrectors 0; consistent yes; residualControl { p 1e-3; U 1e-3; k 1e-3; omega 1e-3; } } potentialFlow { nNonOrthogonalCorrectors 10; } relaxationFactors { equations { U 0.9; k 0.7; omega 0.7; } } cache { grad(U); } fvSchemes ddtSchemes { default steadyState; } gradSchemes { default Gauss linear; grad(U) cellLimited Gauss linear 1; } divSchemes { default none; div(phi,U) bounded Gauss linearUpwindV grad(U); div(phi,k) bounded Gauss upwind; div(phi,omega) bounded Gauss upwind; div((nuEff*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default corrected; } wallDist { method meshWave; } The geometry has approximately 3 million cells. The checkMesh was also ok (see attached image). Thank you very much for your time and I hope someone can help me with this problem. |
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