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February 22, 2019, 15:46 |
interIsoFoam Validation of Weir Flow
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#1 |
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Join Date: Nov 2015
Posts: 38
Rep Power: 11 |
Hello,
I'm trying to validate a weir coefficient using interIsoFoam but have run into an issue (see attached image). If I use the flow depth interface (alpha=0.5), the weir coefficient is much lower than anticipated. If I use the pressure to calculate the head, the weir coefficient is in the expected range. So I am unsure why the pressure matches what would be anticipated but the water surface depth does not. Questions: 1. What would cause the pressure at the interface to be negative? There are ~7 mesh cells between 0Pa and the alpha interface so it isn't negative in just 1 cell (see the line plot in attached image) 2. Is there a way to have the interface correspond to 0Pa? If I change the alpha phase to 0.99 the interface is still negative. 0/U Code:
dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { inlet_water { type flowRateInletVelocity; volumetricFlowRate constant 30; value uniform (0 0 0); } outlet_air { type pressureInletOutletVelocity; value uniform (0 0 0); } outlet_water { type pressureInletOutletVelocity; value uniform (0 0 0); } "(inlet_wall|conc)" { type noSlip; } "(wall1|wall2)" { type symmetry; } "(bed1|bed2)" { type noSlip; } top { type pressureInletOutletVelocity; value uniform (0 0 0); } defaultFaces { type empty; Code:
dimensions [0 0 0 0 0 0 0]; internalField uniform 0; boundaryField { inlet_water { type fixedValue; value uniform 1; outlet_air { type inletOutlet; inletValue uniform 0; value uniform 0; } outlet_water { type inletOutlet; inletValue uniform 1; value uniform 1; } "(inlet_wall|conc)" { type zeroGradient; } "(wall1|wall2)" { type symmetry; } "(bed1|bed2)" { type zeroGradient; } top { type inletOutlet; inletValue uniform 0; value uniform 0; } defaultFaces { type empty; } } 0/p_rgh Code:
dimensions [1 -1 -2 0 0 0 0]; internalField uniform $pressure; boundaryField { inlet_water { type fixedFluxPressure; } outlet_water { type totalPressure; rho rho; psi none; gamma 1; p0 uniform 4286970; value uniform 4286970; } outlet_air { type totalPressure; rho rho; psi none; gamma 1; p0 uniform 0; value uniform 0; } "(inlet_wall|conc)" { type fixedFluxPressure; } "(wall1|wall2)" { type symmetry; } "(bed1|bed2)" { type fixedFluxPressure; } top { type totalPressure; p0 uniform 0; } defaultFaces { type empty; } } fvSchemes Code:
ddtSchemes { default Euler; } gradSchemes { default Gauss linear; } divSchemes { div(rhoPhi,U) Gauss upwind; //Gauss limitedLinearV 1; div(phi,alpha) Gauss upwind; //Gauss vanLeer; div(phirb,alpha) Gauss interfaceCompression; div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear; div(phi,omega) Gauss upwind; div(phi,p_rgh) Gauss upwind; div(phi,k) Gauss upwind; div(phi,epsilon) Gauss upwind; } laplacianSchemes { default Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default corrected; } fluxRequired { default no; p_rgh; pcorr; alpha.water; } fvSolution Code:
solvers { "alpha.water.*" { isoFaceTol 1e-6; surfCellTol 1e-6; nAlphaBounds 3; snapTol 1e-12; clip true; nAlphaSubCycles 1; cAlpha 1; // Note: cAlpha is not used by isoAdvector but must // be specified because interfacePropertes object // reads it during construction. } "pcorr.*" { solver PCG; preconditioner DIC; tolerance 1e-10; relTol 0; } p_rgh { solver GAMG; smoother DICGaussSeidel; tolerance 1e-07; relTol 0.05; } p_rghFinal { $p_rgh; tolerance 1e-07; relTol 0; } "(U|k|omega|epsilon).*" { solver PBiCGStab; preconditioner DILU; tolerance 1e-06; relTol 0; } "(U|k|epsilon)Final" { $U; relTol 0; } } PIMPLE { momentumPredictor no; nCorrectors 3; nOuterCorrectors 1; nNonOrthogonalCorrectors 0; pRefCell 0; pRefValue 0; } relaxationFactors { fields { } equations { ".*" 0.1; } } |
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February 27, 2019, 13:10 |
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#2 |
Member
Join Date: Nov 2015
Posts: 38
Rep Power: 11 |
Additional information:
I'm using snappyHexMesh for the domain and mesh quality is good. The problem persists using interFoam and also doesn't appear to change based on fvSchemes order (1st vs 2nd). And none of the tutorial cases (weirOverflow, waterChannel, damBreak) have the same issue. Any suggestions on where else to look to track this down would be greatly appreciated! |
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interface, interfoam, vof |
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