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residual = nan on iteration 1 with rhoSimpleFoam |
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September 23, 2015, 23:46 |
residual = nan on iteration 1 with rhoSimpleFoam
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#1 |
Senior Member
Join Date: Nov 2010
Location: USA
Posts: 1,232
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Hello folks,
First try using rhoSimpleFoam here. Haven't really done much compressible flow in OpenFOAM before. I have a very simple case of a sphere in a tube. The mesh is about 500k cells and passes all meshCheck just fine. My BCs are all very simple (trying to keep it that way the first time). I have: Inlet (U fixed value, T fixed value, zero grad else) Outlet (p fixed value, zero grad else) and the walls (walls and sphere) which are all set to 0/zeroGradient. However, it seems on my first iteration, all of the residuals are nan's and it crashes very quickly: Time = 1 GAMG: Solving for Ux, Initial residual = nan, Final residual = nan, No Iterations 1000 GAMG: Solving for Uy, Initial residual = nan, Final residual = nan, No Iterations 1000 GAMG: Solving for Uz, Initial residual = nan, Final residual = nan, No Iterations 1000 smoothSolver: Solving for e, Initial residual = nan, Final residual = nan, No Iterations 1000 GAMG: Solving for p, Initial residual = nan, Final residual = nan, No Iterations 1000 time step continuity errors : sum local = nan, global = nan, cumulative = nan rho max/min : 0.025 0.025 GAMG: Solving for omega, Initial residual = nan, Final residual = nan, No Iterations 1000 GAMG: Solving for k, Initial residual = nan, Final residual = nan, No Iterations 1000 ExecutionTime = 389.481 s ClockTime = 389 s I can't seem to figure out why. Did I miss something in my BCs? I set pRefValue manually to be 101325 Pa, so my other BCs and initial condition pressure should be gauge to that. It says that the rho max/min is 0.025 - but the min and max limiter is 0.5 and 1.5, how did it get that low? This is almost STP... There is a defaultFaces patch, but this is just left over from blockMesh and has zero faces, so I shouldn't need to worry about it, right? Here's some of my files: Code:
FoamFile { version 2.0; format ascii; class volVectorField; object U; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 1 -1 0 0 0 0]; internalField uniform (20 0 0); boundaryField { defaultFaces { type fixedValue; value uniform (0 0 0); } inlet { type fixedValue; value uniform (20 0 0); } outlet { type zeroGradient; } wall { type fixedValue; value uniform (0 0 0); } sphere { type fixedValue; value uniform (0 0 0); } } Code:
FoamFile { version 2.0; format ascii; class volScalarField; object p; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [1 -1 -2 0 0 0 0]; internalField uniform 0; boundaryField { defaultFaces { type zeroGradient; } inlet { type zeroGradient; } outlet { type fixedValue; value uniform 0; } wall { type zeroGradient; } sphere { type zeroGradient; } } Code:
FoamFile { version 2.0; format ascii; class volScalarField; object T; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 0 0 1 0 0 0]; internalField uniform 300; boundaryField { defaultFaces { type zeroGradient; } inlet { type fixedValue; value uniform 300; } outlet { type zeroGradient; } wall { type zeroGradient; } sphere { type zeroGradient; } } Code:
dimensions [ 0 2 -2 0 0 0 0 ]; internalField uniform 22.815; boundaryField { defaultFaces { type compressible::kqRWallFunction; value uniform 0; } inlet { type fixedValue; value uniform 22.815; } outlet { type fixedValue; value uniform 22.815; } wall { type compressible::kqRWallFunction; value uniform 0; } sphere { type compressible::kqRWallFunction; value uniform 0; } } Code:
dimensions [ 0 0 -1 0 0 0 0 ]; internalField uniform 477.26; boundaryField { defaultFaces { type compressible::omegaWallFunction; value uniform 0; } inlet { type fixedValue; value uniform 477.76; } outlet { type fixedValue; value uniform 477.76; } wall { type compressible::omegaWallFunction; value uniform 0; } sphere { type compressible::omegaWallFunction; value uniform 0; } } Code:
FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default steadyState; } gradSchemes { default Gauss linear; } divSchemes { default none; div(phi,U) bounded Gauss linearUpwindV Gauss linear; div((muEff*dev2(T(grad(U))))) Gauss linear Gauss linear; div(phi,omega) bounded Gauss linearUpwind Gauss linear; div(phi,k) bounded Gauss linearUpwind Gauss linear; div(phi,Ekp) bounded Gauss linearUpwind Gauss linear; div(phi,e) bounded Gauss linearUpwind Gauss linear; } laplacianSchemes { default Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default corrected; } fluxRequired { default no; p ; } Code:
FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { p { solver GAMG; tolerance 1e-08; relTol 0.05; smoother GaussSeidel; cacheAgglomeration on; nCellsInCoarsestLevel 20; agglomerator faceAreaPair; mergeLevels 1; } U { solver GAMG; tolerance 1e-08; relTol 0.05; smoother GaussSeidel; cacheAgglomeration on; nCellsInCoarsestLevel 20; agglomerator faceAreaPair; mergeLevels 1; } e { solver smoothSolver; smoother GaussSeidel; tolerance 1e-06; relTol 0.1; } "(k|omega)" { $U; tolerance 1e-07; relTol 0.1; } } SIMPLE { nNonOrthogonalCorrectors 0; rhoMin rhoMin [ 1 -3 0 0 0 ] 0.5; rhoMax rhoMax [ 1 -3 0 0 0 ] 1.5; pRefPoint (-4.9 0 0); pRefValue 101325; residualControl { p 1e-2; U 1e-4; e 1e-3; // possibly check turbulence fields "(k|epsilon|omega)" 1e-3; } } relaxationFactors { fields { p 0.3; rho 0.05; } equations { U 0.7; "(k|omega)" 0.7; e 0.5; } } |
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September 25, 2015, 10:55 |
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#2 |
Senior Member
Join Date: Nov 2010
Location: USA
Posts: 1,232
Rep Power: 24 |
Nobody with any clues? Hm. I was going to try and see if I can get it to run in just a pipe.
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September 27, 2015, 21:25 |
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#3 |
New Member
Joseph Urich
Join Date: Mar 2009
Location: Pittsburgh, PA
Posts: 21
Rep Power: 17 |
Hello,
I've always run rhoSimpleFoam using absolute pressures. I don't think pRefValue works the way you describe using it. See this thread http://www.cfd-online.com/Forums/ope...prefvalue.html, section 4.5.3.1 of the user guide, and src/finiteVolume/fvMatrices/fvMatrix/fvMatrix.C; it seems to set the pressure level in one cell only. |
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