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November 2, 2018, 05:32 |
Problem using perfectGas law - OpenFoam v5.x
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#1 |
New Member
Alexandre
Join Date: May 2015
Location: FRANCE
Posts: 8
Rep Power: 11 |
Hello everyone,
I have to model a buoyant cavity using chtMultiRegionFoam under OpenFoam v5. The model is composed of a solid with a hot face and a cold face. The fluid cavity is located inside the solid. The simulation works perfectly fine when the temperature range is around 230K and more. But when I try to lower the cold temperature close to 200K (or under) the simulation diverges after a few timesteps, no matter the timestep size (I even tried 1e-15 s). Do you know if there is a usable range of temperature for the perfectGas law in OpenFoam ? I could not find any information about this. Thank you very much in advance. Alexandre |
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November 2, 2018, 12:54 |
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#2 | |
Senior Member
Deep
Join Date: Oct 2017
Posts: 180
Rep Power: 9 |
Quote:
Hi Alexandre, I haven't used this solver but this doesn't feel like a limitation of OpenFOAM to treat that kind of temperatures. I have a strong feeling that this is due to the numerical schemes. Can you share more details about your case? Perhaps a log file and fvSolution, fvSchemes? |
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November 5, 2018, 05:30 |
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#3 |
New Member
Alexandre
Join Date: May 2015
Location: FRANCE
Posts: 8
Rep Power: 11 |
Hi,
Thank you for replying so quickly. Here is the fvSolution file for the fluid part : Code:
solvers { rho { solver PCG preconditioner DIC; tolerance 1e-7; relTol 0; } rhoFinal { $rho; tolerance 1e-7; relTol 0; } p_rgh { solver PCG; preconditioner DIC; tolerance 1e-7; relTol 0.01; } p_rghFinal { $p_rgh; tolerance 1e-7; relTol 0; } "(U|h|k|epsilon)" { solver PBiCGStab; preconditioner DILU; tolerance 1e-7; relTol 0.1; } "(U|h|k|epsilon)Final" { $U; tolerance 1e-7; relTol 0; } } PIMPLE { momentumPredictor off; nCorrectors 2; nOuterCorrector 100; nNonOrthogonalCorrectors 0; } relaxationFactors { fields { rho 1; p_rgh 0.7; } equations { U 0.3; h 0.5; nuTilda 0.7; k 0.7; epsilon 0.7; "ILambda.*" 0.7; } } Code:
ddtSchemes { default Euler; } gradSchemes { default Gauss linear; } divSchemes { default none; div(phi,U) bounded Gauss upwind; div(phi,K) bounded Gauss linear; div(phi,h) bounded Gauss upwind; div(phi,k) bounded Gauss upwind; div(phi,K) bounded Gauss upwind; div(phi,epsilon) bounded Gauss upwind; div(phi,R) bounded Gauss upwind; div(R) Gauss linear; div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default uncorrected; } fluxRequired { default no; p_rgh; } Code:
Time = 18.6 Pimple iteration 0 Solving for fluid region vInterstice diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCGStab: Solving for h, Initial residual = 0.1908323, Final residual = 9.047866e-08, No Iterations 28 Min/max T:185.6215 24090.01 DICPCG: Solving for p_rgh, Initial residual = 0.3888654, Final residual = 0.003570196, No Iterations 637 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors (vInterstice): sum local = 0.09424987, global = -2.283759e-08, cumulative = 0.07180441 DICPCG: Solving for p_rgh, Initial residual = 0.005414886, Final residual = 9.786837e-08, No Iterations 841 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors (vInterstice): sum local = 3.33313e-06, global = -2.876082e-10, cumulative = 0.07180441 Solving for solid region vIsolant DICPCG: Solving for h, Initial residual = 0.9995731, Final residual = 8.418054e-07, No Iterations 31 DICPCG: Solving for h, Initial residual = 0.2335464, Final residual = 8.814094e-07, No Iterations 32 DICPCG: Solving for h, Initial residual = 0.9849921, Final residual = 9.379368e-07, No Iterations 33 DICPCG: Solving for h, Initial residual = 0.2227003, Final residual = 9.739136e-07, No Iterations 31 DICPCG: Solving for h, Initial residual = 0.9523352, Final residual = 9.676267e-07, No Iterations 33 DICPCG: Solving for h, Initial residual = 0.2217437, Final residual = 9.390169e-07, No Iterations 31 DICPCG: Solving for h, Initial residual = 0.9417496, Final residual = 9.443344e-07, No Iterations 33 DICPCG: Solving for h, Initial residual = 0.2213422, Final residual = 6.281053e-07, No Iterations 32 DICPCG: Solving for h, Initial residual = 0.9365707, Final residual = 9.433744e-07, No Iterations 33 DICPCG: Solving for h, Initial residual = 0.2211105, Final residual = 9.919586e-07, No Iterations 31 DICPCG: Solving for h, Initial residual = 0.9333972, Final residual = 9.359205e-07, No Iterations 33 Min/max T:196.6997 5059.688 ExecutionTime = 283.06 s ClockTime = 288 s Region: vInterstice Courant Number mean: 9.112101 max: 161.0467 Region: vIsolant Diffusion Number mean: 8.590459 max: 1048.57 Time = 18.7 Pimple iteration 0 Solving for fluid region vInterstice diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCGStab: Solving for h, Initial residual = 0.2966009, Final residual = 9.446085e-08, No Iterations 79 Min/max T:-180837.2 1142208 DICPCG: Solving for p_rgh, Initial residual = 0.9999897, Final residual = 0.009953177, No Iterations 89 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors (vInterstice): sum local = 16110.55, global = 0.3987671, cumulative = 0.4705715 DICPCG: Solving for p_rgh, Initial residual = 0.01058313, Final residual = 0.0133549, No Iterations 1001 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors (vInterstice): sum local = 43370.07, global = 0.3987147, cumulative = 0.8692863 Solving for solid region vIsolant DICPCG: Solving for h, Initial residual = 0.9999992, Final residual = 8.675964e-07, No Iterations 61 DICPCG: Solving for h, Initial residual = 0.2509632, Final residual = 7.834133e-07, No Iterations 56 DICPCG: Solving for h, Initial residual = 0.8609676, Final residual = 8.157261e-07, No Iterations 59 DICPCG: Solving for h, Initial residual = 0.5624251, Final residual = 9.31195e-07, No Iterations 56 DICPCG: Solving for h, Initial residual = 0.5685501, Final residual = 9.726149e-07, No Iterations 53 DICPCG: Solving for h, Initial residual = 0.3489626, Final residual = 9.314571e-07, No Iterations 56 DICPCG: Solving for h, Initial residual = 0.4128676, Final residual = 9.384181e-07, No Iterations 56 DICPCG: Solving for h, Initial residual = 0.3065897, Final residual = 9.011148e-07, No Iterations 56 DICPCG: Solving for h, Initial residual = 0.3529538, Final residual = 8.7768e-07, No Iterations 56 DICPCG: Solving for h, Initial residual = 0.3938146, Final residual = 9.657432e-07, No Iterations 51 DICPCG: Solving for h, Initial residual = 0.5516511, Final residual = 9.712179e-07, No Iterations 55 Min/max T:-30780.25 23996.09 ExecutionTime = 289.56 s ClockTime = 294 s Region: vInterstice Courant Number mean: -8368.064 max: 2.690553e+07 Region: vIsolant Diffusion Number mean: 14.09939 max: 6297.303 Time = 18.8 Pimple iteration 0 Solving for fluid region vInterstice diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCGStab: Solving for h, Initial residual = 0.9171763, Final residual = 1.067631e+09, No Iterations 1001 -------------------------------------------------------------------------- MPI_ABORT was invoked on rank 2 in communicator MPI_COMM_WORLD with errorcode 1. NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes. You may or may not see output from other processes, depending on exactly when Open MPI kills them. -------------------------------------------------------------------------- Alexandre |
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November 5, 2018, 10:10 |
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#4 |
Senior Member
Deep
Join Date: Oct 2017
Posts: 180
Rep Power: 9 |
Code:
Region: vInterstice Courant Number mean: 9.112101 max: 161.0467 . . Region: vInterstice Courant Number mean: -8368.064 max: 2.690553e+07 Try following, the output will give you some clues. Code:
checkMesh -allGeometry -allTopology Alternatively, you could also include the following snippet in your controlDict: Code:
adjustTimeStep yes; maxCo 1; maxDeltaT 1e-06; Hope this helps. |
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November 5, 2018, 10:25 |
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#5 |
New Member
Alexandre
Join Date: May 2015
Location: FRANCE
Posts: 8
Rep Power: 11 |
I think that my mesh is fine :
Code:
Overall number of cells of each type: hexahedra: 1453500 prisms: 0 wedges: 0 pyramids: 0 tet wedges: 0 tetrahedra: 0 polyhedra: 0 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Topological cell zip-up check OK. Face-face connectivity OK. Number of regions: 1 (OK). Checking patch topology for multiply connected surfaces... Patch Faces Points Surface topology Bounding box wallIsol 47600 48160 ok (non-closed singly connected) (0 0 0) (0.6 0.3 0.11) fFroide 17100 17381 ok (non-closed singly connected) (0 0 0.11) (0.6 0.3 0.11) fChaude 17100 17381 ok (non-closed singly connected) (0 0 0) (0.6 0.3 0) Checking geometry... Overall domain bounding box (0 0 0) (0.6 0.3 0.11) Mesh has 3 geometric (non-empty/wedge) directions (1 1 1) Mesh has 3 solution (non-empty) directions (1 1 1) Boundary openness (1.828863e-17 9.979202e-17 1.261745e-17) OK. Max cell openness = 1.719864e-16 OK. Max aspect ratio = 11.11111 OK. Minimum face area = 4.5e-07. Maximum face area = 1.846875e-05. Face area magnitudes OK. Min volume = 1.2e-09. Max volume = 2.4625e-08. Total volume = 0.0198. Cell volumes OK. Mesh non-orthogonality Max: 0 average: 0 Non-orthogonality check OK. Face pyramids OK. Max skewness = 3.08396e-13 OK. Coupled point location match (average 0) OK. Face tets OK. Min/max edge length = 0.00045 0.005 OK. All angles in faces OK. Face flatness (1 = flat, 0 = butterfly) : min = 1 average = 1 All face flatness OK. Cell determinant (wellposedness) : minimum: 0.03693746 average: 3.696978 Cell determinant check OK. Concave cell check OK. Face interpolation weight : minimum: 0.1085973 average: 0.4962515 Face interpolation weight check OK. Face volume ratio : minimum: 0.1218274 average: 0.9907908 Face volume ratio check OK. Mesh OK. End The simulation works perfectly with Thot = 260K and Tcold = 230K with a timestep of 0.1s but it diverges completly with Thot = 240K and Tcold = 210K, even with a timestep of 1e-15s. That is why I was asking about a usable temperature range of some laws in OpenFoam. |
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November 16, 2018, 10:22 |
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#6 |
New Member
Alexandre
Join Date: May 2015
Location: FRANCE
Posts: 8
Rep Power: 11 |
Dear all,
I think I've come up with a solution to my problem. In the fvSchemes file, I changed the boundedGauss upwind to the Gauss upwind schemes and the snGrad from uncorrected to corrected, and it worked. But I still do not know why. Does anyone have an idea ? Best regards, Alexandre |
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chtmultiregionfoam, perfectgas, temperature |
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