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Old   August 10, 2009, 22:21
Default Questions about Cross-Arrhenius and Cross-WLF viscosity model
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Jitao Liu
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Hi 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

Jitao
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Old   August 13, 2009, 04:56
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Sandy Lee
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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
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Old   August 13, 2009, 05:11
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Sandy Lee
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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

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Old   August 13, 2009, 06:41
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Jitao Liu
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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
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Old   August 13, 2009, 06:56
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Jitao Liu
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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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