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- - **Questions about Cross-Arrhenius and Cross-WLF viscosity model**
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Questions about Cross-Arrhenius and Cross-WLF viscosity modelHi all,
I want to use Cross-Arrhenius and Cross-WLF viscosity model in OpenFOAM. I have added these two models on OF1.5-dev. But when running test case with Cross-Arrhenius or Cross-WLF viscosity model, I always get "Floating point exception" errors. hw@linux-szab:~/OpenFOAM/hw-1.5-dev/run/mycase/CrossArrheniusTest/3dHoleFill> interHeatFoam /*---------------------------------------------------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 1.5-dev | | \\ / A nd | Revision: exported | | \\/ M anipulation | Web: http://www.OpenFOAM.org | \*---------------------------------------------------------------------------*/ Exec : interHeatFoam Date : Aug 11 2009 Time : 09:30:50 Host : linux-szab PID : 6543 Case : /home/hw/OpenFOAM/hw-1.5-dev/run/mycase/CrossArrheniusTest/3dHoleFill nProcs : 1 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create mesh for time = 0 Reading environmentalProperties Reading transportProperties Reading field T Reading field pd Reading field gamma Reading field U Reading/calculating face flux field phi Reading transportProperties Selecting incompressible transport model CrossArrhenius Selecting incompressible transport model Newtonian Calculating field g.h time step continuity errors : sum local = 0.000497512, global = -0.000497512, cumulative = -0.000497512 PCG: Solving for pcorr, Initial residual = 1, Final residual = 9.96481e-11, No Iterations 205 time step continuity errors : sum local = 5.32932e-14, global = -2.90909e-16, cumulative = -0.000497512 Courant Number mean: 0.0302752 max: 1 velocity magnitude: 1.13422 Starting time loop Courant Number mean: 0.0147684 max: 0.487805 velocity magnitude: 1.13422 deltaT = 0.000487805 Time = 0.000487805 MULES: Solving for gamma Liquid phase volume fraction = 0.000121344 Min(gamma) = 0 Max(gamma) = 1 MULES: Solving for gamma Liquid phase volume fraction = 0.000242689 Min(gamma) = 0 Max(gamma) = 1 PCG: Solving for pd, Initial residual = 1, Final residual = 0.0498813, No Iterations 101 PCG: Solving for pd, Initial residual = 4.22676e-05, Final residual = 1.88871e-06, No Iterations 99 PCG: Solving for pd, Initial residual = 2.69834e-05, Final residual = 9.36861e-08, No Iterations 113 PBiCG: Solving for T, Initial residual = 1, Final residual = 5.32086e-08, No Iterations 8 time step continuity errors : sum local = 9.39573e-07, global = 1.93984e-08, cumulative = -0.000497493 ExecutionTime = 1.24 s ClockTime = 1 s Courant Number mean: 0.0148266 max: 0.487805 velocity magnitude: 1.27619 deltaT = 0.000487805 Time = 0.00097561 MULES: Solving for gamma Liquid phase volume fraction = 0.000364033 Min(gamma) = 0 Max(gamma) = 1 MULES: Solving for gamma Liquid phase volume fraction = 0.000485378 Min(gamma) = 0 Max(gamma) = 1 PCG: Solving for pd, Initial residual = 0.167474, Final residual = 0.00669526, No Iterations 3 PCG: Solving for pd, Initial residual = 0.00214774, Final residual = 9.61768e-05, No Iterations 24 PCG: Solving for pd, Initial residual = 0.000964297, Final residual = 9.11502e-08, No Iterations 134 PBiCG: Solving for T, Initial residual = 0.939648, Final residual = 1.866e-08, No Iterations 7 time step continuity errors : sum local = 4.48573e-06, global = 9.73087e-09, cumulative = -0.000497483 ExecutionTime = 1.71 s ClockTime = 2 s Courant Number mean: 0.0204435 max: 3.50076 velocity magnitude: 14.3531 deltaT = 6.94321e-05 Time = 0.00104504 MULES: Solving for gamma Liquid phase volume fraction = 0.00050265 Min(gamma) = 0 Max(gamma) = 1 MULES: Solving for gamma Liquid phase volume fraction = 0.000519921 Min(gamma) = 0 Max(gamma) = 1 PCG: Solving for pd, Initial residual = 0.00017547, Final residual = 8.32853e-06, No Iterations 58 PCG: Solving for pd, Initial residual = 3.5553e-25, Final residual = 3.5553e-25, No Iterations 0 PCG: Solving for pd, Initial residual = 5.58968e-25, Final residual = 5.58968e-25, No Iterations 0 PBiCG: Solving for T, Initial residual = 1, Final residual = 8.1607e-08, No Iterations 2 time step continuity errors : sum local = 0.000373548, global = -1.5779e-05, cumulative = -0.000513262 ExecutionTime = 2.02 s ClockTime = 2 s Courant Number mean: 0.00156255 max: 0.153382 velocity magnitude: 4.4182 deltaT = 8.31358e-05 Time = 0.00112818 Floating point exception Can anybody help me to fix it, thanks in advance. Kind regards Jitaohttp://www.cfd-online.com/home/hw/De...B%C2%B6/01.png |

by the way...Hi Jitao,
By the way, do you know where I can find those values nu0, nuInf, m, n, k to different phase names at different temperatures about CrossPowerLawCoeffs and BirdCarreauCoeffs viscosity models?? Thanks a lot. Sandy |

Hi Jitao,
your max Courant Number exceed 0.5, so you should make the deltT more smaller; the pd equation can not be solved smoothly. I guess the boundary conditions about pd are wrong. Why you not check it again. You also can choose "upwind" scheme to solve pd. Maybe you can get better convergence. But, if BCs are wrong, everything is air. In addition, your solver namely "interHeatFoam" is about phase change, right? I use the versition 1.5, so I can not try it. Sandy |

Hi Sandy,
Thanks for your reply. Firstly, I add energy equation to the interHeatFoam sover which is based on interFoam. The viscosity dissipation is consided in TEqn. Secondly, I set the adjustTimeStep "yes" in controlDict. The pd boundary is zeroGradient . I will test the "upwind" scheme for pd. Thirdly, I am interested in the polymer melt flow behavier in injection molding process. The values of plastic's viscosity model coefficients can be found in Plastic Handbooks or in some of the literatures. The comercial tools such as MoldFlow and PolyFlow contain these coefficients too. Best wishes, Jitao |

3 Attachment(s)
P.S.
When using Cross-Arrhenius viscosity model, if I set the coefficient β to zero, the calculation runs well. May be there is somthing unreasonable in my solver and my visosity model (Cross-Arrhenius and Cross-WLF). I 'll pay more attention to it. Jitao |

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