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- - **Heat transfer simulation with low-Re modelling blowing up**
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Heat transfer simulation with low-Re modelling blowing upHi,
I am simulating atmospheric boundary layer flow over an inclined plate with application to solar panels. I am looking into the heat transfer from the panel. At the domain inlet, I am using mean profiles of velocity, turbulent kinetic energy and specific dissipation rate of turbulence using SST k-omega turbulence model. At the outlet of the domain I am using fixed pressure of 0 Pa. Without low-Re mesh (y+ around 200), for getting pressures on the panel (for wind load estimation), simulations runs fine. However for the heat transfer simulations with y+<1, simulation is blowing up as the courant number gets bigger and bigger (even with time step size of 10^-9 s) although wind speed is low for the heat transfer case (5 m/s at 10m height whereas for the wind loading simulation I have used 25 m/s without no problem). I am using buoyantBoussinesqPimpleFoam solver for the heat transfer simulation. My fvSchemes for heat transfer looks like the following: ddtSchemes { default Euler; } gradSchemes { default cellLimited leastSquares 1.0; } divSchemes { default none; div(phi,U) Gauss vanLeer; div(phi,T) Gauss vanLeer; div(phi,k) Gauss vanLeer; div(phi,omega) Gauss vanLeer ; div(phi,R) Gauss vanLeer ; div(R) Gauss limitedLinear 1 ; div((nuEff*dev(T(grad(U))))) Gauss linear limited 0.5 ; } laplacianSchemes { default none; laplacian(nuEff,U) Gauss linear limited 0.5; laplacian((1|A(U)),p_rgh) Gauss linear limited 0.5 ; laplacian(kappaEff,T) Gauss linear limited 0.5; laplacian(DkEff,k) Gauss linear limited 0.5; laplacian(DomegaEff,omega) Gauss linear limited 0.5; laplacian(DREff,R) Gauss linear limited 0.5; } interpolationSchemes { default linear; } snGradSchemes { default limited 0.5; } fluxRequired { default no; p_rgh ; } Below is a glimpse when simulation is blowing up --------------------------------------------------------------------- Time = 0.00010097 Courant Number mean: 4.7345636e-07 max: 1233.7809 PIMPLE: iteration 1 DILUPBiCG: Solving for T, Initial residual = 1.2870124e-06, Final residual = 7.1891992e-09, No Iterations 2 DICPCG: Solving for p_rgh, Initial residual = 0.76361335, Final residual = 0.00097027484, No Iterations 120 time step continuity errors : sum local = 1.4489948e-10, global = 9.5209982e-12, cumulative = -6.5187104e-12 PIMPLE: iteration 2 DILUPBiCG: Solving for T, Initial residual = 2.5226717e-06, Final residual = 8.3556918e-09, No Iterations 101 DICPCG: Solving for p_rgh, Initial residual = 0.69872336, Final residual = 0.00098344698, No Iterations 419 time step continuity errors : sum local = 4.5798547e-10, global = 1.8186047e-11, cumulative = 1.1667336e-11 DILUPBiCG: Solving for omega, Initial residual = 0.00050378054, Final residual = 5.0894516e-09, No Iterations 109 bounding omega, min: -1.6530455e+12 max: 3.8839584e+12 average: 59305422 DILUPBiCG: Solving for k, Initial residual = 0.00035940466, Final residual = 5.3762244e-09, No Iterations 99 bounding k, min: -8.6846115e+11 max: 2.7713031e+12 average: 1585310.7 ExecutionTime = 13894.57 s ClockTime = 13905 s Time = 0.00010098 Courant Number mean: 6.9096584e-07 max: 2692.3661 PIMPLE: iteration 1 DILUPBiCG: Solving for T, Initial residual = 3.1575455e-06, Final residual = 9.7394175e-09, No Iterations 2 DICPCG: Solving for p_rgh, Initial residual = 0.74447529, Final residual = 0.00097299859, No Iterations 97 time step continuity errors : sum local = 2.4875275e-10, global = 1.7993474e-11, cumulative = 2.9660811e-11 PIMPLE: iteration 2 DILUPBiCG: Solving for T, Initial residual = 3.7889403e-06, Final residual = 5.7741675e-09, No Iterations 153 DICPCG: Solving for p_rgh, Initial residual = 0.7661894, Final residual = 0.00099395397, No Iterations 444 time step continuity errors : sum local = 2.5940091e-09, global = 8.240833e-11, cumulative = 1.1206914e-10 DILUPBiCG: Solving for omega, Initial residual = 0.00087259239, Final residual = 8.3974792e-09, No Iterations 79 bounding omega, min: -7.5412548e+11 max: 1.9226682e+12 average: 94265063 DILUPBiCG: Solving for k, Initial residual = 0.0015909616, Final residual = 8.3691303e-09, No Iterations 68 bounding k, min: -3.2118556e+11 max: 2.0770441e+12 average: 4234488.5 ExecutionTime = 14445.9 s ClockTime = 14456 s Time = 0.00010099 Courant Number mean: 1.9504303e-06 max: 5747.6202 PIMPLE: iteration 1 DILUPBiCG: Solving for T, Initial residual = 1.6991088e-05, Final residual = 2.6964904e-09, No Iterations 4 DICPCG: Solving for p_rgh, Initial residual = 0.75607356, Final residual = 0.00099111414, No Iterations 201 time step continuity errors : sum local = 8.4048694e-10, global = 3.4520769e-10, cumulative = 4.5727683e-10 PIMPLE: iteration 2 DILUPBiCG: Solving for T, Initial residual = 2.9118025e-05, Final residual = 7.2186118e-09, No Iterations 419 DICPCG: Solving for p_rgh, Initial residual = 0.84296989, Final residual = 0.00095307524, No Iterations 706 time step continuity errors : sum local = 4.7938114e-09, global = 1.1318495e-09, cumulative = 1.5891263e-09 DILUPBiCG: Solving for omega, Initial residual = 0.0067051264, Final residual = 7.1001411e-09, No Iterations 328 bounding omega, min: -1.4353841e+14 max: 1.3961573e+14 average: 1.7683567e+09 DILUPBiCG: Solving for k, Initial residual = 0.0091318156, Final residual = 9.0899654e-09, No Iterations 214 bounding k, min: -6.8698845e+11 max: 1.075334e+13 average: 19477433 ExecutionTime = 15914.84 s ClockTime = 15926 s Time = 0.000101 Courant Number mean: 9.2903545e-06 max: 33446.887 PIMPLE: iteration 1 DILUPBiCG: Solving for T, Initial residual = 3.5918305e-05, Final residual = 7.4009402e-09, No Iterations 3 DICPCG: Solving for p_rgh, Initial residual = 0.51530912, Final residual = 0.00098150633, No Iterations 87 time step continuity errors : sum local = 5.6978294e-09, global = 1.1952208e-09, cumulative = 2.7843471e-09 PIMPLE: iteration 2 DILUPBiCG: Solving for T, Initial residual = 9.5350344e-05, Final residual = 6.6825388e-07, No Iterations 1001 DICPCG: Solving for p_rgh, Initial residual = 0.64166418, Final residual = 0.026321393, No Iterations 1001 time step continuity errors : sum local = 1.7760159e-06, global = 1.8077374e-09, cumulative = 4.5920845e-09 DILUPBiCG: Solving for omega, Initial residual = 0.02237984, Final residual = 6.0043179e-09, No Iterations 420 bounding omega, min: -4.1960305e+14 max: 2.2858488e+14 average: 7.0990082e+08 DILUPBiCG: Solving for k, Initial residual = 0.009506604, Final residual = 0.0018439062, No Iterations 1001 bounding k, min: -1.7533181e+15 max: 8.382294e+14 average: -3.8906711e+08 ExecutionTime = 19251.27 s ClockTime = 19265 s Time = 0.00010101 Courant Number mean: 2.9411928e-05 max: 42822.926 PIMPLE: iteration 1 DILUPBiCG: Solving for T, Initial residual = 0.011547178, Final residual = 4.2007322e-09, No Iterations 7 DICPCG: Solving for p_rgh, Initial residual = 0.5517749, Final residual = 0.00098472085, No Iterations 87 time step continuity errors : sum local = 1.9706388e-08, global = 1.9126112e-09, cumulative = 6.5046957e-09 PIMPLE: iteration 2 DILUPBiCG: Solving for T, Initial residual = 0.00045584686, Final residual = 5.7580162e-07, No Iterations 1001 DICPCG: Solving for p_rgh, Initial residual = 0.79932465, Final residual = 0.21947454, No Iterations 1001 time step continuity errors : sum local = 4.5888733e-05, global = 2.4650819e-09, cumulative = 8.9697776e-09 DILUPBiCG: Solving for omega, Initial residual = 0.046824604, Final residual = 0.42651976, No Iterations 1001 bounding omega, min: -2.9120631e+16 max: 7.5610454e+15 average: -1.7510987e+10 DILUPBiCG: Solving for k, Initial residual = 0.10073936, Final residual = 0.053489969, No Iterations 1001 bounding k, min: -6.1933141e+14 max: 5.4698344e+14 average: -1.1146877e+09 ExecutionTime = 23333.7 s ClockTime = 23350 s Time = 0.00010102 Courant Number mean: 0.00057248341 max: 283410.74 PIMPLE: iteration 1 DILUPBiCG: Solving for T, Initial residual = 0.84933889, Final residual = 2.0178504e-09, No Iterations 9 DICPCG: Solving for p_rgh, Initial residual = 0.91110456, Final residual = 0.00098260631, No Iterations 202 time step continuity errors : sum local = 2.6226461e-07, global = -4.8494379e-08, cumulative = -3.9524602e-08 PIMPLE: iteration 2 DILUPBiCG: Solving for T, Initial residual = 0.033386681, Final residual = 0.014155016, No Iterations 1001 DICPCG: Solving for p_rgh, Initial residual = 0.80383648, Final residual = 5.7958476, No Iterations 1001 time step continuity errors : sum local = 0.020399066, global = -9.6567685e-09, cumulative = -4.918137e-08 DILUPBiCG: Solving for omega, Initial residual = 0.98880096, Final residual = 11962.323, No Iterations 1001 bounding omega, min: -6.4680894e+24 max: 3.2921399e+25 average: 5.2212511e+19 DILUPBiCG: Solving for k, Initial residual = 0.014781795, Final residual = 3.0990057e-08, No Iterations 1001 bounding k, min: -4.8263648e+14 max: 5.4072665e+14 average: 1.0635891e+09 ExecutionTime = 27448.32 s ClockTime = 27467 s Time = 0.00010103 Courant Number mean: 0.045544987 max: 5.2721582e+08 PIMPLE: iteration 1 DILUPBiCG: Solving for T, Initial residual = 0.49369191, Final residual = 7.5375708e-09, No Iterations 7 DICPCG: Solving for p_rgh, Initial residual = 0.96557631, Final residual = 0.00099907484, No Iterations 238 time step continuity errors : sum local = 3.3753698e-05, global = 7.2331754e-06, cumulative = 7.183994e-06 PIMPLE: iteration 2 DILUPBiCG: Solving for T, Initial residual = 0.88776239, Final residual = 50.198586, No Iterations 1001 DICPCG: Solving for p_rgh, Initial residual = 0.0023242099, Final residual = 1.4577883, No Iterations 1001 time step continuity errors : sum local = 171.529, global = 1.7893858e-06, cumulative = 8.9733799e-06 ------------------------------------------------------------------ I'll be really glad if someone helps me dealing with this problem and getting my simulation running. Thanks. Jubayer |

Have you tried using different input for the divergence and laplacian schemes?
divergence as "Gauss upwind" and laplacian as "Gauss linear corrected", especially for the parts where you use k and omega. These schemes have worked for me with different simulations. If you really need to use the schemes that you have as an input now, I would start from these easier schemes and switch over to more advanced schemes step by step. |

hello,
Your time step seems too big, since your Co number is getting higer and higer ... Try to lower your time step, or use adaptative time stepping. regards, olivier |

Hi Roman,
Thanks for your advice. I'll try those schemes. However, I used simpler schemes before, but did not work. Lets hope this time it works. Jubayer |

Hi Olivier,
I thought of the time step size at first. But as you can see, I have even used 10^-09 s for this full scale simulation, lowering time step size more than that does not make sense. This made me belief that the problem is somewhere else. Thanks for your input. Jubayer |

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