# bounding epsilon blow up

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 September 30, 2010, 11:42 bounding epsilon blow up #1 New Member   Jie (Jay) Zhang Join Date: Sep 2010 Location: FL, U.S. Posts: 25 Rep Power: 8 Sponsored Links 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 BC setting: epsilo: wall { type epsilonWallFunction; Cmu 0.09; kappa 0.41; E 9.8; value uniform 0.0012; } inlet { type fixedValue; value uniform 0.0012; } outlet { type zeroGradient; }

 September 30, 2010, 11:46 #2 New Member   Jie (Jay) Zhang Join Date: Sep 2010 Location: FL, U.S. Posts: 25 Rep Power: 8 I'm new to FOAM. I will be very appreciated for your help!

 September 30, 2010, 20:07 #3 Senior Member     Santiago Marquez Damian Join Date: Aug 2009 Location: Santa Fe, Santa Fe, Argentina Posts: 430 Rep Power: 17 Maybe a draft of the geometry, details of problem and system/controlDict system/fvSchemes system/dvSolution 0/* dictionaries can give us a better idea how to solve the blowing up. Regards. __________________ Santiago MÁRQUEZ DAMIÁN, Ph.D. Research Scientist 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. http://www.cimec.org.ar

 October 8, 2010, 17:11 #4 Senior Member   Travis Carrigan Join Date: Jul 2010 Location: Arlington, TX Posts: 147 Rep Power: 9 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 #5 New Member   Philipp Bachmann Join Date: May 2010 Location: Esslingen, Germany Posts: 7 Rep Power: 9 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. greetz phil

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