|September 30, 2010, 11:42||
bounding epsilon blow up
Jie (Jay) Zhang
Join Date: Sep 2010
Location: FL, U.S.
Posts: 25Rep Power: 8
It is a case using simpleFoam solver with K-epsilon Turbulence model.
the fellowing result will blow up. Is there anyone can help me to find out where the problem comes from? BC setting('epsilo' attached)?
Time = 0.001
DILUPBiCG: Solving for Ux, Initial residual = 0.64936, Final residual = 0.0285001, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.527993, Final residual = 0.0462129, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.815427, Final residual = 0.0168725, No Iterations 2
DICPCG: Solving for p, Initial residual = 1.42064e-15, Final residual = 1.42064e-15, No Iterations 0
time step continuity errors : sum local = 6.86127e+27, global = 7.64441e+11, cumulative = -2.2062e+23
DILUPBiCG: Solving for epsilon, Initial residual = 4.35678e-07, Final residual = 4.35678e-07, No Iterations 0
bounding epsilon, min: 3.3635e-22 max: 1.18516e+87 average: 7.77262e+80
DILUPBiCG: Solving for k, Initial residual = 5.98618e-09, Final residual = 5.98618e-09, No Iterations 0
ExecutionTime = 193.75 s ClockTime = 195 s
value uniform 0.0012;
value uniform 0.0012;
|September 30, 2010, 20:07||
Santiago Marquez Damian
Join Date: Aug 2009
Location: Santa Fe, Santa Fe, Argentina
Posts: 430Rep Power: 16
Maybe a draft of the geometry, details of problem and
dictionaries can give us a better idea how to solve the blowing up.
Santiago MÁRQUEZ DAMIÁN, Ph.D.
Research Center for Computational Methods (CIMEC) - CONICET/UNL
Tel: 54-342-4511594 Int. 7032
Colectora Ruta Nac. 168 / Paraje El Pozo
(3000) Santa Fe - Argentina.
|October 8, 2010, 17:11||
Join Date: Jul 2010
Location: Arlington, TX
Posts: 147Rep Power: 8
Try setting the k and e schemes to upwind rather than linear in the fvSchemes directory. I've had problems achieving convergence using second order schemes for the turbulence models.
|January 16, 2011, 18:14||
Join Date: May 2010
Location: Esslingen, Germany
Posts: 7Rep Power: 8
In my case it was a great help to reduce the relaxation factors. I had the same problem. The relaxation factors are responsible for the search of a the start value in the calculation of the parameters depending of the result in the last time step. If you reduce them, the start value is not so far away to the last result but you´ll need more time for the calculation.
Try it. You find the relaxationFactors in fvSolution and then reduce all factors 0.1 down. If it doesn´t help, try 0.2.
It could be the geometry, too. But try it.
Hope, it helps.
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