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November 17, 2018, 16:07 |
Weird Courant Number Error in Couette Flow
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#1 |
Member
Emre
Join Date: Nov 2015
Location: Izmir, Turkey
Posts: 97
Rep Power: 11 |
Hello everyone,
I encounter incomprehensible Courant number errors and velocity magnitudes when I try to simulate 2D Couette flow. U file: Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | foam-extend: Open Source CFD | | \\ / O peration | Version: 4.0 | | \\ / A nd | Web: http://www.foam-extend.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class volVectorField; object U; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { movingWall { type fixedValue; value uniform (1 0 0); } stationaryWall { type fixedValue; value uniform (0 0 0); } inlet { type zeroGradient; } outlet { type zeroGradient; } frontAndBack { type empty; } } Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | foam-extend: Open Source CFD | | \\ / O peration | Version: 4.0 | | \\ / A nd | Web: http://www.foam-extend.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class volScalarField; object p; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -2 0 0 0 0]; internalField uniform 0; boundaryField { movingWall { type zeroGradient; } stationaryWall { type zeroGradient; } inlet { type fixedValue; value uniform 0; } outlet { type fixedValue; value uniform 0; } frontAndBack { type empty; } } Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | foam-extend: Open Source CFD | | \\ / O peration | Version: 4.0 | | \\ / A nd | Web: http://www.foam-extend.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // convertToMeters 1; vertices ( (0 0 0) (1 0 0) (1 0.25 0) (0 0.25 0) (0 0 0.1) (1 0 0.1) (1 0.25 0.1) (0 0.25 0.1) ); blocks ( hex (0 1 2 3 4 5 6 7) (400 400 1) simpleGrading (1 1 1) ); edges ( ); boundary ( movingWall { type wall; faces ( (3 7 6 2) ); } inlet { type patch; faces ( (0 4 7 3) ); } outlet { type patch; faces ( (2 6 5 1) ); } stationaryWall { type wall; faces ( (1 5 4 0) ); } frontAndBack { type empty; faces ( (0 3 2 1) (4 5 6 7) ); } ); mergePatchPairs ( ); Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | foam-extend: Open Source CFD | | \\ / O peration | Version: 4.0 | | \\ / A nd | Web: http://www.foam-extend.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object controlDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // application icoFoam; startFrom startTime; startTime 0; stopAt endTime; endTime 3; deltaT 0.001; writeControl runTime; writeInterval 1; purgeWrite 0; writeFormat ascii; writePrecision 6; writeCompression uncompressed; timeFormat general; timePrecision 6; runTimeModifiable yes; Code:
Time = 0.044 Courant Number mean: 0.336637 max: 1944.94 velocity magnitude: 2431.17 BiCGStab: Solving for Ux, Initial residual = 0.972023, Final residual = 9.93918e-06, No Iterations 80 BiCGStab: Solving for Uy, Initial residual = 0.945448, Final residual = 6.14037e-06, No Iterations 82 DICPCG: Solving for p, Initial residual = 0.849381, Final residual = 9.71391e-07, No Iterations 521 time step continuity errors : sum local = 6.37445e-07, global = 9.354e-09, cumulative = 1.45292e-08 DICPCG: Solving for p, Initial residual = 0.920578, Final residual = 9.38132e-07, No Iterations 543 time step continuity errors : sum local = 9.62929e-06, global = 9.33402e-08, cumulative = 1.07869e-07 ExecutionTime = 133.78 s ClockTime = 134 s Time = 0.045 Courant Number mean: 168.34 max: 1.37785e+06 velocity magnitude: 3.28688e+06 BiCGStab: Solving for Ux, Initial residual = 0.999994, Final residual = 3.24586e+18, No Iterations 1000 BiCGStab: Solving for Uy, Initial residual = 0.999935, Final residual = 3.48908e+16, No Iterations 1000 DICPCG: Solving for p, Initial residual = 1, Final residual = 2.42732e-08, No Iterations 3 time step continuity errors : sum local = 1.36528e+17, global = 1.55905e+10, cumulative = 1.55905e+10 DICPCG: Solving for p, Initial residual = 0.985689, Final residual = 1.29964e-08, No Iterations 3 time step continuity errors : sum local = 1.3758e+17, global = -3.67509e+13, cumulative = -3.67353e+13 ExecutionTime = 148.01 s ClockTime = 148 s Time = 0.046 Courant Number mean: 6.45818e+24 max: 6.04572e+27 velocity magnitude: 1.51143e+28 Floating point exception (core dumped) Sincerely, ordinary |
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