# Negative alpha1 using interDyMFoam

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 February 21, 2013, 11:06 Negative alpha1 using interDyMFoam #1 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 6 Hi, I am currently trying to do a simulation with a high speed water jet acting on rotating Pelton buckets. Unfortunately, the simulation crashes before giving me any results. The alpha1 minimum volume fractions are negative, and I wonder if this is what is making the simulation crash? I am not sure about the setup of fvSolution and fvSchemes, so my guess is that these cause the negative alphas. The log output of some early timesteps: Code: ```Interface Courant Number mean: 1.624315938e-07 max: 0.1091097517 Courant Number mean: 0.000375590931 max: 0.1091097517 deltaT = 3.491717999e-07 Time = 1.533552435e-06 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 1.533552435e-06 transformation: ((0 0 0) (0.9999999987 (0 5.078761069e-05 0))) AMI: Creating addressing and weights between 14964 source faces and 14964 target faces AMI: Patch source weights min/max/average = 0.9950716382, 1.394205984, 1.000575435 AMI: Patch target weights min/max/average = 0.9950442673, 1.365096275, 1.000564816 Execution time for mesh.update() = 1.58 s MULES: Solving for alpha1 Phase-1 volume fraction = 5.44966545e-07 Min(alpha1) = -1.791466825e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 5.823644789e-07 Min(alpha1) = -1.038904174e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 6.197624128e-07 Min(alpha1) = -7.825973141e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 6.571603467e-07 Min(alpha1) = -4.473487596e-20 Max(alpha1) = 1 GAMG: Solving for p_rgh, Initial residual = 0.01655311958, Final residual = 6.810976661e-09, No Iterations 15 time step continuity errors : sum local = 1.769268728e-15, global = 1.368834199e-17, cumulative = -4.282017598e-08 GAMG: Solving for p_rgh, Initial residual = 0.003952141467, Final residual = 6.617702388e-09, No Iterations 11 time step continuity errors : sum local = 1.400029147e-15, global = -1.456483218e-16, cumulative = -4.282017612e-08 GAMG: Solving for p_rgh, Initial residual = 0.001011700049, Final residual = 3.845282687e-09, No Iterations 10 time step continuity errors : sum local = 8.217598588e-16, global = -5.254782802e-17, cumulative = -4.282017618e-08 GAMG: Solving for p_rgh, Initial residual = 0.000554491584, Final residual = 6.972409284e-09, No Iterations 9 time step continuity errors : sum local = 1.490644691e-15, global = -1.291619314e-16, cumulative = -4.282017631e-08 GAMG: Solving for p_rgh, Initial residual = 0.0003465827588, Final residual = 5.393514794e-09, No Iterations 9 time step continuity errors : sum local = 1.153062298e-15, global = 1.070930183e-16, cumulative = -4.28201762e-08 GAMGPCG: Solving for p_rgh, Initial residual = 0.0002396514594, Final residual = 2.174711367e-10, No Iterations 5 time step continuity errors : sum local = 4.64927874e-17, global = -3.972436362e-19, cumulative = -4.28201762e-08 ExecutionTime = 223.19 s ClockTime = 233 s Interface Courant Number mean: 1.916717685e-07 max: 0.1287661148 Courant Number mean: 0.0004432945119 max: 0.1287661148 deltaT = 4.019038676e-07 Time = 1.935456303e-06 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 1.935456303e-06 transformation: ((0 0 0) (0.9999999979 (0 6.409771126e-05 0))) AMI: Creating addressing and weights between 14964 source faces and 14964 target faces AMI: Patch source weights min/max/average = 0.9932927434, 1.400417156, 1.000607698 AMI: Patch target weights min/max/average = 0.9925058446, 1.363865653, 1.000594273 Execution time for mesh.update() = 1.59 s MULES: Solving for alpha1 Phase-1 volume fraction = 7.002037891e-07 Min(alpha1) = -3.274013142e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 7.432472314e-07 Min(alpha1) = -6.563983597e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 7.862906737e-07 Min(alpha1) = -1.433173356e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 8.293341161e-07 Min(alpha1) = -1.93310652e-20 Max(alpha1) = 1 GAMG: Solving for p_rgh, Initial residual = 0.01412494318, Final residual = 5.132243665e-09, No Iterations 15 time step continuity errors : sum local = 1.437750713e-15, global = 1.507869969e-17, cumulative = -4.282017618e-08 GAMG: Solving for p_rgh, Initial residual = 0.003289228668, Final residual = 8.303451587e-09, No Iterations 11 time step continuity errors : sum local = 2.021746186e-15, global = -1.823752452e-16, cumulative = -4.282017637e-08 GAMG: Solving for p_rgh, Initial residual = 0.0009262395848, Final residual = 9.932632803e-09, No Iterations 9 time step continuity errors : sum local = 2.455684309e-15, global = -3.964969215e-16, cumulative = -4.282017676e-08 GAMG: Solving for p_rgh, Initial residual = 0.0004916397871, Final residual = 6.729308374e-09, No Iterations 9 time step continuity errors : sum local = 1.664547207e-15, global = -1.628362513e-16, cumulative = -4.282017693e-08 GAMG: Solving for p_rgh, Initial residual = 0.000302596381, Final residual = 4.941746421e-09, No Iterations 9 time step continuity errors : sum local = 1.222443575e-15, global = 1.240361068e-16, cumulative = -4.28201768e-08 GAMGPCG: Solving for p_rgh, Initial residual = 0.0002065366047, Final residual = 1.986903846e-10, No Iterations 5 time step continuity errors : sum local = 4.914866401e-17, global = -3.566772216e-19, cumulative = -4.28201768e-08 ExecutionTime = 252.05 s ClockTime = 263 s``` My fvSolution: Code: ```/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { pcorr { solver PCG; preconditioner { preconditioner GAMG; tolerance 1e-05; relTol 0; smoother DICGaussSeidel; nPreSweeps 0; nPostSweeps 2; nFinestSweeps 2; cacheAgglomeration false; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } tolerance 1e-05; relTol 0; maxIter 100; } p_rgh { solver GAMG; tolerance 1e-08; relTol 0; smoother DIC; nPreSweeps 0; nPostSweeps 2; nFinestSweeps 2; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } p_rghFinal { solver PCG; preconditioner { preconditioner GAMG; tolerance 2e-09; relTol 0; nVcycles 2; smoother DICGaussSeidel; nPreSweeps 2; nPostSweeps 2; nFinestSweeps 2; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } tolerance 2e-09; relTol 0; maxIter 20; } U { solver smoothSolver; smoother GaussSeidel; tolerance 1e-06; relTol 0; nSweeps 1; } } PIMPLE { momentumPredictor no; nCorrectors 6; nNonOrthogonalCorrectors 0; nAlphaCorr 1; nAlphaSubCycles 4; cAlpha 1.5; correctPhi no; } relaxationFactors { fields { } equations { "U.*" 1; } } // ************************************************************************* //``` My fvSchemes: Code: ```/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default Euler; } gradSchemes { default Gauss linear; } divSchemes { div(rho*phi,U) Gauss upwind; div(phi,alpha) Gauss vanLeer; div(phirb,alpha) Gauss interfaceCompression; } laplacianSchemes { default Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default corrected; } fluxRequired { default no; p_rgh; pcorr; alpha; } // ************************************************************************* //```

 February 21, 2013, 12:43 #2 Senior Member     Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,261 Rep Power: 23 I don't think so. The values are so small that they shouldn't be causing any problems. __________________ *On twitter @akidTwit *Spend as much time formulating your questions as you expect people to spend on their answer.

 February 22, 2013, 05:58 #3 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 6 Hi, Thank you for your response! In that case there must be another reason for the simulation to crash. I get the error message: Code: ``` [1] #0 Foam::error::printStack(Foam::Ostream&) in "/opt/openfoam211/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [1] #1 Foam::sigFpe::sigHandler(int) in "/opt/openfoam211/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [1] #2 in "/lib/x86_64-linux-gnu/libc.so.6" [1] #3 Foam::divide(Foam::Field&, double const&, Foam::UList const&) in "/opt/openfoam211/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" [1] #4 [1] in "/opt/openfoam211/platforms/linux64GccDPOpt/bin/interDyMFoam" [1] #5 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6" [1] #6 [1] in "/opt/openfoam211/platforms/linux64GccDPOpt/bin/interDyMFoam" [IEPT0938:10436] *** Process received signal *** [IEPT0938:10436] Signal: Floating point exception (8) [IEPT0938:10436] Signal code: (-6) [IEPT0938:10436] Failing at address: 0x3e9000028c4 [IEPT0938:10436] [ 0] /lib/x86_64-linux-gnu/libc.so.6(+0x364a0) [0x7f5d484a84a0] [IEPT0938:10436] [ 1] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x35) [0x7f5d484a8425] [IEPT0938:10436] [ 2] /lib/x86_64-linux-gnu/libc.so.6(+0x364a0) [0x7f5d484a84a0] [IEPT0938:10436] [ 3] /opt/openfoam211/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(_ZN4Foam6divideERNS_5FieldIdEERKdRKNS_5UListIdEE+0x24) [0x7f5d495e3754] [IEPT0938:10436] [ 4] interDyMFoam() [0x427714] [IEPT0938:10436] [ 5] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed) [0x7f5d4849376d] [IEPT0938:10436] [ 6] interDyMFoam() [0x42f14d] [IEPT0938:10436] *** End of error message *** -------------------------------------------------------------------------- mpirun noticed that process rank 1 with PID 10436 on node IEPT0938 exited on signal 8 (Floating point exception). --------------------------------------------------------------------------``` The last two time steps: Code: ```Interface Courant Number mean: 2.578325543e-06 max: 0.1973915059 Courant Number mean: 0.001834300267 max: 0.5267375298 deltaT = 1.428571429e-06 Time = 0.0003242857143 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 0.0003242857143 transformation: ((0 0 0) (0.9999423314 (0 0.01073936544 0))) AMI: Creating addressing and weights between 14964 source faces and 14964 target faces AMI: Patch source weights min/max/average = 0.1315257649, 1.892722733, 1.003533756 AMI: Patch target weights min/max/average = 0.07925273668, 1.723012618, 1.002725914 Execution time for mesh.update() = 1.77 s MULES: Solving for alpha1 Phase-1 volume fraction = 0.0001384376939 Min(alpha1) = -1.218465399e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 0.000138641559 Min(alpha1) = -3.245414137e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 0.0001388454241 Min(alpha1) = -3.091100792e-19 Max(alpha1) = 1 GAMG: Solving for p_rgh, Initial residual = 0.0002908184194, Final residual = 1.591419563e-06, No Iterations 4 time step continuity errors : sum local = 1.816358047e-11, global = 1.740532506e-12, cumulative = -4.267707731e-07 GAMGPCG: Solving for p_rgh, Initial residual = 6.862589785e-05, Final residual = 4.269590466e-10, No Iterations 5 time step continuity errors : sum local = 4.889981776e-15, global = 1.051027885e-16, cumulative = -4.26770773e-07 ExecutionTime = 3892.75 s ClockTime = 4152 s Interface Courant Number mean: 2.588344877e-06 max: 0.1973759562 Courant Number mean: 0.001834365716 max: 0.5267375298 deltaT = 1.428571429e-06 Time = 0.0003257142857 solidBodyMotionFunctions::rotatingMotion::transformation(): Time = 0.0003257142857 transformation: ((0 0 0) (0.9999418221 (0 0.01078667359 0))) AMI: Creating addressing and weights between 14964 source faces and 14964 target faces AMI: Patch source weights min/max/average = 4.265623869e-06, 1.919686291, 1.003500292 AMI: Patch target weights min/max/average = 0, 1.724940936, 1.00242754 Execution time for mesh.update() = 2.1 s MULES: Solving for alpha1 Phase-1 volume fraction = 0.0001390492891 Min(alpha1) = -1.396734536e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 0.0001392531541 Min(alpha1) = -7.3958564e-21 Max(alpha1) = 1 MULES: Solving for alpha1 Phase-1 volume fraction = 0.0001394570191 Min(alpha1) = -2.633820368e-20 Max(alpha1) = 1``` I used a bit different fvSolutions and fvSchemes now, it seems these are better settings for my simulation. fvSolution: Code: ```/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers { pcorr { solver PCG; preconditioner { preconditioner GAMG; tolerance 1e-05; relTol 0; smoother DICGaussSeidel; nPreSweeps 0; nPostSweeps 2; nFinestSweeps 2; cacheAgglomeration false; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } tolerance 1e-05; relTol 0; maxIter 100; } p_rgh { solver GAMG; tolerance 1e-08; relTol 0.01; smoother DIC; nPreSweeps 0; nPostSweeps 2; nFinestSweeps 2; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } p_rghFinal { solver PCG; preconditioner { preconditioner GAMG; tolerance 2e-09; relTol 0; nVcycles 2; smoother DICGaussSeidel; nPreSweeps 2; nPostSweeps 2; nFinestSweeps 2; cacheAgglomeration true; nCellsInCoarsestLevel 10; agglomerator faceAreaPair; mergeLevels 1; } tolerance 2e-09; relTol 0; maxIter 20; } U { solver smoothSolver; smoother GaussSeidel; tolerance 1e-06; relTol 0; nSweeps 1; } } PIMPLE { momentumPredictor no; nCorrectors 2; nNonOrthogonalCorrectors 0; nAlphaCorr 1; nAlphaSubCycles 3; cAlpha 1.5; correctPhi no; pRefPoint (0.0013 0.0017 0.0017); pRefValue 1e5; } relaxationFactors { fields { } equations { "U.*" 1; } } // ************************************************************************* //``` fvSchemes: Code: ```/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default Euler; } gradSchemes { default Gauss linear; } divSchemes { div(rho*phi,U) Gauss vanLeerV; div(phi,alpha) Gauss vanLeer; div(phirb,alpha) Gauss vanLeer; } laplacianSchemes { default Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default corrected; } fluxRequired { default no; p_rgh; pcorr; alpha; } // ************************************************************************* //``` I can't figure out why it crashes, there does not seem to be an issue with the Courant number.

 February 22, 2013, 06:08 #4 Senior Member     Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,261 Rep Power: 23 If you're still having problems, try the following: Test maxAlphaCo=0.1. Keep the momentum predictor enabled. Try relTol=0 on p_rgh, and finally try running GAMG with pure GaussSeidel instead of using DIC. __________________ *On twitter @akidTwit *Spend as much time formulating your questions as you expect people to spend on their answer.

 February 22, 2013, 06:27 #5 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 6 Thank you very much for your quick reply! I will try that and let you know if it works or not.

 February 22, 2013, 09:08 #6 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 6 Crashed again unfortunately, at the same time as before. Does the error message make any sense? Code: ```[1] #0 Foam::error::printStack(Foam::Ostream&) at ??:? [1] #1 Foam::sigFpe::sigHandler(int) at ??:? [1] #2 in "/lib/x86_64-linux-gnu/libc.so.6" [1] #3 at symmTensorField.C:? [1] #4 [1] at ??:? [1] #5 [1] at ??:? [1] #6 [1] at ??:? [1] #7 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6" [1] #8 [1] at ??:? [IEPT0955:30806] *** Process received signal *** [IEPT0955:30806] Signal: Floating point exception (8) [IEPT0955:30806] Signal code: (-6) [IEPT0955:30806] Failing at address: 0x3e900007856 [IEPT0955:30806] [ 0] /lib/x86_64-linux-gnu/libc.so.6(+0x364a0) [0x7ff907d934a0] [IEPT0955:30806] [ 1] /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x35) [0x7ff907d93425] [IEPT0955:30806] [ 2] /lib/x86_64-linux-gnu/libc.so.6(+0x364a0) [0x7ff907d934a0] [IEPT0955:30806] [ 3] /opt/openfoam211/platforms/linux64GccDPOpt/lib/libOpenFOAM.so(+0x3ac9c4) [0x7ff908ee19c4] [IEPT0955:30806] [ 4] interDyMFoam() [0x4782e2] [IEPT0955:30806] [ 5] interDyMFoam() [0x478844] [IEPT0955:30806] [ 6] interDyMFoam() [0x42a9e0] [IEPT0955:30806] [ 7] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed) [0x7ff907d7e76d] [IEPT0955:30806] [ 8] interDyMFoam() [0x42f14d] [IEPT0955:30806] *** End of error message *** -------------------------------------------------------------------------- mpirun noticed that process rank 1 with PID 30806 on node IEPT0955 exited on signal 8 (Floating point exception). -------------------------------------------------------------------------- jonerivr@IEPT0955:~/OpenFOAM/jonerivr-2.1.1/run/donut-mesh13\$``` I have two more ideas about what can be wrong, other than the fv-files: 1. I am simulating with turbulenceProperties set to laminar, while a turbulence model should in reality be applied. 2. I have a symmetryplane along the jet and have heard that this BC sometimes causes instabilities with multiphase-simulations. Does this sound reasonable? I will try to run some more simulations during the weekend. For k and epsilon i will use: k=2.45504; //k=(2/3)(Uref*Ti)², Ti=0,05 turb intensity (Versteeg, 2007) epsilon=255.38893; //epsilon=0,0845^(3/4)*(k^(3/2))/(0,07L) L=Diameter of jet=0,04

February 22, 2013, 09:57
#7
Senior Member

Olivier
Join Date: Jun 2009
Location: France, grenoble
Posts: 265
Rep Power: 11
Hello,

You are using interDyMFoam with AMI i guess. On your last iteration befor crash, you get :
Quote:
 AMI: Patch target weights min/max/average = 0.0792527 ...
This mean that there is some trouble at the interface. (value should be close to 1).
Solution: either improve your mesh, or lower your time stepping a bit may help.

regards,
olivier

February 22, 2013, 10:06
#8
Member

Anon
Join Date: Oct 2012
Posts: 33
Rep Power: 6
Quote:
 Originally Posted by olivierG This mean that there is some trouble at the interface. (value should be close to 1). Solution: either improve your mesh, or lower your time stepping a bit may help.
Thank you Olivier!

As you can see in the screenshot below, the AMI-patches are not perfectly circular (AMI1 and AMI2 showing). I guess that might be what is causing it to crash?

I guess I should go back to snappyHexMesh then, and refine the AMI-interface further.

 February 22, 2013, 10:17 #9 Senior Member   Olivier Join Date: Jun 2009 Location: France, grenoble Posts: 265 Rep Power: 11 hello, Finer interface doesn't help here (and this may even be worst !). What's matter is your mesh should not overlap or create hole: try a different "matchTolerance" in your boundary file, and check your geometry (interface should be circular). And if you want good result with AMI, try to use an more uniform mesh at interface, i.e not a fine on one side, and coarse on the other. regards, olivier

February 22, 2013, 10:46
#10
Member

Anon
Join Date: Oct 2012
Posts: 33
Rep Power: 6
Quote:
 Originally Posted by olivierG Finer interface doesn't help here (and this may even be worst !). What's matter is your mesh should not overlap or create hole: try a different "matchTolerance" in your boundary file, and check your geometry (interface should be circular). And if you want good result with AMI, try to use an more uniform mesh at interface, i.e not a fine on one side, and coarse on the other.
Thank you Olivier!

So you mean that if I increase the matchTolerance, e.g. from 0.0001 to 0.001, my simulation might be more stable?

The problem is that the interface is not perfectly circular. I tried to adjust the settings in snappyHexMeshDict, but I couldn't figure out how to resolve it. The mesh in the interface gets affected by the geometries around, resulting in "bumps" several places around the interface. Please see the attached images for explanation.

Any tips and tricks to improve my mesh and simulation are greatly appreciated!

Regards,

Jone

Whole domain, rotating region with buckets and stationary part with water jet:

"Bump" created in the AMI-interface because of buckets:

 February 26, 2013, 05:13 #11 Senior Member   Christian Lucas Join Date: Aug 2009 Location: Braunschweig, Germany Posts: 202 Rep Power: 11 Hi, have you tried using div(phi,alpha) Gauss vanLeer01 this scheme should bound alpha between 0 and 1 Regards, Christian

February 26, 2013, 05:39
#12
Member

Anon
Join Date: Oct 2012
Posts: 33
Rep Power: 6
Quote:
 Originally Posted by Chris Lucas have you tried using div(phi,alpha) Gauss vanLeer01 this scheme should bound alpha between 0 and 1
No, I have not tried this, but I will definitely do so. Thanks a lot!

I am currently working on making a better mesh, hope to achieve this today so I can try running the simulation again. It turns out that a circular AMI-interface is difficult to obtain together with the refinements I want, but I think I will manage somehow.

 February 27, 2013, 03:50 #13 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 6 I finally got the simulation running, but I discovered some weird behavior of the flow so far. 1. The jet gets cut when meeting the AMI-interface, spreading along the AMI-patches on both sides (picture 1). 2. A hole is created in the isovolume at the jet inlet (picture 2). Still, when I check the value of alpha1 graphically in paraView (see picture 3), it seems that alpha1 has the max value in those cells. Has anyone seen this type of behavior before? Regards, Jone Picture 1: Picture 2: Picture 3:

 March 1, 2013, 07:59 #14 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 6 I wonder if anyone has an idea of what is causing these effects? There seems to be a strong diffusion of the jet. The behavior along the symmetryPlane is very strange, as I would expect the water to have the maximum speed (38.38ms-1) along this. Problematic effects:The jet looses its shape quickly The jet is "cut" and water spreads out along the AMI-patches (left and right of jet) Strange "crater" at the start of the jet Jet does not seem to be mirrored along the symmetryPlane Here is a picture with another mesh. It shows an isovolume with 0.1

 March 2, 2013, 11:26 #15 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 6 Anyone? I tried to check the effect of the symmetryPlane by replacing it with zeroGradient for U, p_rgh and alpha1. As you can see from the pictures it looks a lot better (though far from perfect) with the zeroGradient BC. Is there a bug in the symmetryPlane-condition? symmetryPlane BC applied to patch: zeroGradient BC applied to patch:

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