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 okroud June 5, 2012 11:13

Temperature in simpleFoam takes lots of Iterations

Hey Guys,

i added temperature to simpleFoam as described in this Tutorial for icoFoam.
Everything works fine, though the Solution needs a lot of Time since the Solving for T needs about 500 Iterations, which themselves require noticeable more time than the other variables. I've waited nearly a day and it doesn't get better. Is is a large Mesh so i it would be great if anyone had any experience in whether this is preventable or maybe necessary?

The entry in fvSolution is:

T
{
solver BICCG;
preconditioner DILU;
tolerance 1e-7;
relTol 0;
};

The entries in fvSchemes are:

divSchemes
{
div(phi,T) Gauss upwind;
}

laplacianSchemes
{
default Gauss linear corrected;
}

Here an extract of the log-File:

DILUPBiCG: Solving for Ux, Initial residual = 0.00100392, Final residual = 1.55987e-06, No Iterations 3
DILUPBiCG: Solving for Uy, Initial residual = 0.000223085, Final residual = 1.98551e-06, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.00409009, Final residual = 2.67272e-06, No Iterations 4
DICPCG: Solving for p, Initial residual = 0.0102603, Final residual = 0.000508878, No Iterations 10
time step continuity errors : sum local = 0.00022309, global = -3.75985e-05, cumulative = -0.0631543
DILUPBiCG: Solving for omega, Initial residual = 1.34598e-05, Final residual = 1.55138e-06, No Iterations 1
bounding omega, min: -55157.8 max: 7.30739e+06 average: 74327.1
DILUPBiCG: Solving for k, Initial residual = 0.00209203, Final residual = 3.94547e-06, No Iterations 3
bounding k, min: -0.000121144 max: 1.54218 average: 0.0210219
DILUPBiCG: Solving for T, Initial residual = 0.000117996, Final residual = 9.23239e-08, No Iterations 527
ExecutionTime = 80799 s ClockTime = 80875 s

This is my first question in this Forum, so i hope everything is fine, thanks for answers!

 Chris Lucas June 6, 2012 03:12

Hi,

set "relTol" to "0.1"

Best Regards,
Christian

 okroud June 6, 2012 05:09

Thank you Chris, now it does about 300 Iterations which is already much better!

 sdharmar October 19, 2012 00:42

Same problem with p

Quote:
 Originally Posted by Chris Lucas (Post 364955) Hi, set "relTol" to "0.1" Best Regards, Christian
DILUPBiCG: Solving for Ux, Initial residual = 0.239894, Final residual = 0.0179294, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.179769, Final residual = 0.0125606, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.641576, Final residual = 0.0401016, No Iterations 1
DICPCG: Solving for p, Initial residual = 0.0565956, Final residual = 0.00545759, No Iterations 679
time step continuity errors : sum local = 10.8709, global = 0.0357859, cumulative = 1.01927
DILUPBiCG: Solving for epsilon, Initial residual = 0.100542, Final residual = 0.00703845, No Iterations 1
DILUPBiCG: Solving for k, Initial residual = 0.200465, Final residual = 0.0159354, No Iterations 1
ExecutionTime = 246.64 s ClockTime = 250 s

Please let me know how cope up with this.

 meindert October 19, 2012 00:50

Try using a multi-grid (GAMG) solver for the pressure equation, and have a look at the motorBike tutorial to get an impression on how to use it.

 sdharmar October 19, 2012 01:35

Meindert,

Thank you for quick reply I'll try this.

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