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Stability Issues - Compressible Turbomachinery Flow |
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Lorenz
Join Date: Jun 2023
Location: Austria
Posts: 11
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Hello Foamers,
i have been struggling for a couple of weeks with stability problems along the walls in a turbomachinery case. Problem description: On the pressure side of the blade, i do have instabilities spots. Only the limiters keep the fields in bound. At those spots the pressure and tempreature hits both limiters. Quite interesting is that the only occur on one side of the blade. I have tried different schemes (from upwind, linear, to TVDs), different wall functions, different URFs and both rhoSimpleFoam and rhoPimpleFoam with pseudo-transient option. attached some images at different time steps. Case description: The APU Testcase consisting of a stator <> rotor <> diffuser. Interface treatment between the cellzones is done using the mixing plane approach (tested and should not be the source of the problem). The rotor is part of a MRF Zone. It is a transonic case. Mesh was generated using TurboGrid. Mesh report: Code:
/*---------------------------------------------------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2212 | | \\ / A nd | Website: www.openfoam.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ Build : _095c9bc4-20230626 OPENFOAM=2212 patch=230612 version=v2212 Arch : "LSB;label=32;scalar=64" Exec : checkMesh -allTopology -allGeometry Date : Apr 25 2024 Time : 17:13:19 Host : Lenovo-Lorenz PID : 558712 I/O : uncollated Case : /home/lorenz/OpenFOAM/lorenz-v2212/run/APU_cases/APU_turboGrid_pimple2 nProcs : 1 trapFpe: Floating point exception trapping enabled (FOAM_SIGFPE). fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 5, maxFileModificationPolls 20) allowSystemOperations : Allowing user-supplied system call operations // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Mesh stats points: 2434284 faces: 7083874 internal faces: 6868460 cells: 2325389 faces per cell: 6 boundary patches: 20 point zones: 2 face zones: 7 cell zones: 7 Overall number of cells of each type: hexahedra: 2325389 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: 3 The mesh has multiple regions which are not connected by any face. <<Writing region information to "7000/cellToRegion" <<Writing region 0 (fully disconnected) with 158760 cells to cellSet region0 <<Writing region 1 (fully disconnected) with 1453620 cells to cellSet region1 <<Writing region 2 (fully disconnected) with 713009 cells to cellSet region2 Checking geometry... Overall domain bounding box (-0.0226722 0.000935012 -5.4927e-06) (0.0371807 0.078873 0.15) Mesh has 3 geometric (non-empty/wedge) directions (1 1 1) Mesh has 3 solution (non-empty) directions (1 1 1) Boundary openness (4.83671e-16 -4.78226e-16 -1.51663e-16) OK. Max cell openness = 3.25411e-15 OK. Max aspect ratio = 246.427 OK. Minimum face area = 4.72401e-11. Maximum face area = 7.3442e-06. Face area magnitudes OK. Min volume = 2.55561e-15. Max volume = 2.26138e-09. Total volume = 5.24996e-05. Cell volumes OK. Mesh non-orthogonality Max: 64.7177 average: 16.1112 Non-orthogonality check OK. Face pyramids OK. Max skewness = 2.36707 OK. Coupled point location match (average 0) OK. Face tets OK. Min/max edge length = 2.24722e-06 0.005336 OK. <<Writing 6106 near (closer than 1.79327e-07 apart) points to set nearPoints All angles in faces OK. Face flatness (1 = flat, 0 = butterfly) : min = 0.991675 average = 0.999997 All face flatness OK. Cell determinant (wellposedness) : minimum: 2.2949e-06 average: 0.373766 ***Cells with small determinant (< 0.001) found, number of cells: 26935 <<Writing 26935 under-determined cells to set underdeterminedCells Concave cell check OK. Face interpolation weight : minimum: 0.353969 average: 0.486807 Face interpolation weight check OK. Face volume ratio : minimum: 0.472079 average: 0.943948 Face volume ratio check OK. Calculating AMI weights between owner patch: ROTORPER1 and neighbour patch: ROTORPER2 AMI: Creating addressing and weights between 18830 source faces and 18830 target faces AMI: Patch source sum(weights) min:0.998521 max:1.00022 average:0.999996 AMI: Patch target sum(weights) min:0.998627 max:1.00022 average:0.999996 Calculating AMI weights between owner patch: STATORPER1 and neighbour patch: STATORPER2 AMI: Creating addressing and weights between 6519 source faces and 6519 target faces AMI: Patch source sum(weights) min:0.999683 max:1.00001 average:0.999999 AMI: Patch target sum(weights) min:0.999681 max:1.00001 average:0.999998 Calculating AMI weights between owner patch: DIFFUSERPER1 and neighbour patch: DIFFUSERPER2 AMI: Creating addressing and weights between 3780 source faces and 3780 target faces AMI: Patch source sum(weights) min:0.999094 max:1.00006 average:1 AMI: Patch target sum(weights) min:0.999216 max:1.00006 average:1 Failed 1 mesh checks. End Inlet conditions have been ramped up to gently initialise the case.
Solver settings fvSolution: Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | foam-extend: Open Source CFD | | \\ / O peration | Version: 5.0 | | \\ / A nd | Web: http://www.foam-extend.org | | \\/ M anipulation | For copyright notice see file Copyright | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { p { solver PBiCGStab; //preconditioner DIC; // non-transonic preconditioner DILU; // transonic option tolerance 1e-06; relTol 0.001; minIter 3; } pFinal { $p; relTol 0; minIter 2; } "(U.*|h.*|e.*)" { solver PBiCGStab; preconditioner DILU; tolerance 1e-08; relTol 0; minIter 2; } "(k.*|omega.*|epsilon.*)" { $U; } "rho.*" { solver diagonal; } Phi { solver PBiCGStab; preconditioner diagonal; tolerance 0; relTol 0.01; minIter 4; } } potentialFlow { nNonOrthogonalCorrectors 3; } PIMPLE { turbOnFinalIterOnly false; momentumPredictor yes; transonic yes; consistent yes; nCorrectors 3; nNonOrthogonalCorrectors 2; nOuterCorrectors 1; pMin 1e4; pMax 5.5e5; maxCo 0.3; rDeltaTSmoothingCoeff 0.1; rDeltaTDampingCoeff 0.9; maxDeltaT 1; } relaxationFactors { /* equations { ".*" 1; }*/ fields {p 0.7; rho 0.5; U 0.7; "(h|e)" 0.7; "omega|k" 0.7;} equations { U 0.7://tablse ((0 0.4) (5000 0.4) (7000 0.7) (10000 0.7)); p 0.9;//table ((0 0.3) (5000 0.3) (7000 0.5) (10000 0.7)); "(h|e)" 0.7;//table ((0 0.3) (5000 0.3) (7000 0.4) (10000 0.7)); "(omega|k)" 0.7;//table ((0 0.3) (5000 0.3) (7000 0.4) (10000 0.7)); ".*Final" 0.9; } } // ************************************************************************* // Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | foam-extend: Open Source CFD | | \\ / O peration | Version: 5.0 | | \\ / A nd | Web: http://www.foam-extend.org | | \\/ M anipulation | For copyright notice see file Copyright | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default localEuler; } gradSchemes { //default leastSquares; //default Gauss linear; default cellMDLimited Gauss linear 1; grad(p) cellMDLimited Gauss linear 0.333; grad(h) cellMDLimited Gauss linear 0.333; } divSchemes { default none; div(phi,U) Gauss vanLeerV;//bounded Gauss limitedLinear 1; div(phid,p) Gauss limitedLinear 1; energy Gauss limitedLinear 1 ;// upwind; //limitedLinear 1; //bounded Gauss upwind; // div(phi,K) Gauss linear; div(phi,h) $energy; turbulence Gauss limitedLinear 1; //bounded Gauss upwind; // div(phi,k) $turbulence; div(phi,omega) $turbulence; div((phi|interpolate(rho)),p) Gauss vanLeer; div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear; } laplacianSchemes { default Gauss linear limited 1; } interpolationSchemes { default linear; } snGradSchemes { default limited 1; } wallDist { method meshWave; // Optionally correct distance from near-wall cells to the boundary //correctWalls true; } // Mixing plane mixingPlane { default areaAveraging; p areaAveraging; U areaAveraging; k fluxAveraging; epsilon fluxAveraging; omega fluxAveraging; //NOTE: Ideally, tangential velocity components should also be //fluxAveraged, while keeping areaAveraging for normal velocity //component (to preserve perfect mass conservation) } // ************************************************************************* // Code:
Time = 7809 PIMPLE: iteration 1 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 velocityDampingConstraint dampU damped 0 (0%) of cells, with max limit 800 DILUPBiCGStab: Solving for Ux, Initial residual = 0.000249435, Final residual = 6.81517e-09, No Iterations 3 DILUPBiCGStab: Solving for Uy, Initial residual = 0.00080509, Final residual = 8.87449e-09, No Iterations 3 DILUPBiCGStab: Solving for Uz, Initial residual = 0.000569909, Final residual = 3.82422e-09, No Iterations 4 limitVelocity limitU Limited 0 (0%) of cells, 0 (0%) of faces, with max limit 1000 DILUPBiCGStab: Solving for h, Initial residual = 0.000384002, Final residual = 4.19852e-09, No Iterations 3 limitTemperature limitT Lower limited 0 (0%) of cells, with min limit 250 limitTemperature limitT Upper limited 0 (0%) of cells, with max limit 1000 limitTemperature limitT Unlimited Tmin 252.019 limitTemperature limitT Unlimited Tmax 477.591 DILUPBiCGStab: Solving for p, Initial residual = 0.000140561, Final residual = 1.85169e-09, No Iterations 3 DILUPBiCGStab: Solving for p, Initial residual = 1.98267e-05, Final residual = 7.22618e-10, No Iterations 3 DILUPBiCGStab: Solving for p, Initial residual = 3.35463e-06, Final residual = 4.2684e-10, No Iterations 3 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 2.33584e-06, global = 1.73819e-06, cumulative = 0.00179875 limitVelocity limitU Limited 0 (0%) of cells, 0 (0%) of faces, with max limit 1000 DILUPBiCGStab: Solving for p, Initial residual = 8.94487e-07, Final residual = 3.21931e-10, No Iterations 3 DILUPBiCGStab: Solving for p, Initial residual = 3.14635e-07, Final residual = 2.34587e-10, No Iterations 3 DILUPBiCGStab: Solving for p, Initial residual = 1.63798e-07, Final residual = 1.5646e-10, No Iterations 3 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 5.00591e-07, global = 4.19009e-07, cumulative = 0.00179917 limitVelocity limitU Limited 0 (0%) of cells, 0 (0%) of faces, with max limit 1000 DILUPBiCGStab: Solving for p, Initial residual = 1.15935e-07, Final residual = 1.29116e-10, No Iterations 3 DILUPBiCGStab: Solving for p, Initial residual = 7.72638e-08, Final residual = 9.41494e-11, No Iterations 3 DILUPBiCGStab: Solving for p, Initial residual = 5.8621e-08, Final residual = 4.05603e-10, No Iterations 2 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 2.56025e-07, global = 2.32087e-07, cumulative = 0.00179941 limitVelocity limitU Limited 0 (0%) of cells, 0 (0%) of faces, with max limit 1000 DILUPBiCGStab: Solving for omega, Initial residual = 2.49722e-05, Final residual = 7.15876e-10, No Iterations 2 DILUPBiCGStab: Solving for k, Initial residual = 0.000620142, Final residual = 3.8175e-09, No Iterations 4 ExecutionTime = 6009.19 s ClockTime = 6009 s Checking flux 'phi' balance across non-conformal boundary patches: Interface pair (ROTORPER1, ROTORPER2) : Interface type: cyclicAMI Area: 0.00109392 0.00109392 Diff = 9.72366e-11 or 8.88884e-06 % Flux: 0.0292392 0.0292392 Diff = 1.92815e-08 or 6.59439e-05 % Interface pair (STATORPER1, STATORPER2) : Interface type: cyclicAMI Area: 0.000148424 0.000148424 Diff = -5.6034e-11 or 3.77525e-05 % Flux: 0.0318963 0.0318963 Diff = 3.01887e-08 or 9.46464e-05 % Interface pair (DIFFUSERPER1, DIFFUSERPER2) : Interface type: cyclicAMI Area: 0.00446935 0.00446935 Diff = 9.86112e-10 or 2.20639e-05 % Flux: 0.108133 0.108133 Diff = -5.51434e-08 or 5.09957e-05 % Interface pair (STATORMIXOUT, ROTORMIXIN) : Interface type: mixingPlane Area: 0.000127884 0.000151862 Diff = -2.39781e-05 or 15.7894 % Flux: 0.0207961 0.0245887 Diff = -0.00379257 or 15.4241 % Scaled flux: 0.0207961 0.0207063 Diff = 8.98321e-05 or 0.431966 % Interface pair (ROTORMIXOUT, DIFFUSERMIXIN) : Interface type: mixingPlane Area: 0.000237219 0.000237219 Diff = -4.87891e-19 or 2.05671e-13 % Flux: 0.0190978 0.0190425 Diff = 5.33628e-05 or 0.279419 % Scaled flux: 0.0190978 0.0190425 Diff = 5.33628e-05 or 0.279419 % fieldMinMax fminmax write: min/max(mag(U)) = 0 651.465 min/max(rho) = 0.41633 3.94753 min/max(k) = 9.57422e-09 7049.24 min/max(p) = 55890.9 414275 min/max(T) = 252.104 477.591 min/max(omega) = 7948.92 1.42849e+09
__________________
Lorenz H. PhD Student Montanuniversity Leoben |
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Tags |
compressible, instability, mrf, pseudotransient, turbomachinery |
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