# Calculation of k and epsilon freezes

 Register Blogs Members List Search Today's Posts Mark Forums Read

 November 13, 2012, 05:13 Calculation of k and epsilon freezes #1 New Member   Join Date: Sep 2012 Posts: 26 Rep Power: 4 Hi all, I've got a problem with my calculation von k and epsilon. I'm trying to simulate a rotating geometry with a modified version of interFoam. The geometry is rotating in different directions and my fluid is sloshing, but the values for k and epsilon just dont chance anymore after some iterations. At the beginning there are some Iterations for k and epsilon Code: ```MULES: Solving for alpha1 Liquid phase volume fraction = 0.979575 Min(alpha1) = -2.49977e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 0.979575 Min(alpha1) = -7.02031e-21 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 0.979575 Min(alpha1) = -1.31893e-20 Max(alpha1) = 1 MULES: Solving for alpha1 Liquid phase volume fraction = 0.979575 Min(alpha1) = -4.39865e-20 Max(alpha1) = 1 DICPCG: Solving for p_rgh, Initial residual = 0.00109002, Final residual = 8.85396e-08, No Iterations 124 time step continuity errors : sum local = 1.83749e-09, global = 2.10194e-11, cumulative = -6.24155e-11 DICPCG: Solving for p_rgh, Initial residual = 0.000154468, Final residual = 9.29858e-08, No Iterations 114 time step continuity errors : sum local = 1.93264e-09, global = -1.87438e-10, cumulative = -2.49854e-10 DICPCG: Solving for p_rgh, Initial residual = 2.61918e-05, Final residual = 9.23886e-08, No Iterations 79 time step continuity errors : sum local = 1.9189e-09, global = 2.37918e-10, cumulative = -1.19357e-11 DILUPBiCG: Solving for epsilon, Initial residual = 0.000340262, Final residual = 6.24431e-09, No Iterations 2 bounding epsilon, min: -4.02028e-08 max: 0.107857 average: 5.80718e-05 DILUPBiCG: Solving for k, Initial residual = 0.000539149, Final residual = 1.33527e-11, No Iterations 4 bounding k, min: -7.24082e-12 max: 0.00100971 average: 1.00796e-05 ExecutionTime = 17.68 s ClockTime = 18 s``` but later on, at about 0.2s (first directionchange is at 0.5s) it pretty much looks like this: Code: ```MULES: Solving for alpha1 Liquid phase volume fraction = 0.979575 Min(alpha1) = -2.15831e-20 Max(alpha1) = 1.00001 MULES: Solving for alpha1 Liquid phase volume fraction = 0.979575 Min(alpha1) = -2.96242e-20 Max(alpha1) = 1.00001 MULES: Solving for alpha1 Liquid phase volume fraction = 0.979575 Min(alpha1) = -1.20443e-20 Max(alpha1) = 1.00001 MULES: Solving for alpha1 Liquid phase volume fraction = 0.979575 Min(alpha1) = -9.61596e-21 Max(alpha1) = 1.00001 DICPCG: Solving for p_rgh, Initial residual = 0.000269819, Final residual = 9.59801e-08, No Iterations 26 time step continuity errors : sum local = 1.39057e-09, global = 1.24122e-10, cumulative = -4.05415e-08 DICPCG: Solving for p_rgh, Initial residual = 1.5512e-05, Final residual = 9.55703e-08, No Iterations 21 time step continuity errors : sum local = 1.3846e-09, global = 1.14579e-10, cumulative = -4.04269e-08 DICPCG: Solving for p_rgh, Initial residual = 1.98201e-06, Final residual = 9.75346e-08, No Iterations 5 time step continuity errors : sum local = 1.41305e-09, global = 1.08762e-10, cumulative = -4.03181e-08 DILUPBiCG: Solving for epsilon, Initial residual = 0.00010125, Final residual = 7.4232e-09, No Iterations 1 bounding epsilon, min: 1.98379e-18 max: 16.2816 average: 0.00581568 DILUPBiCG: Solving for k, Initial residual = 9.96483e-11, Final residual = 9.96483e-11, No Iterations 0 ExecutionTime = 936.41 s ClockTime = 977 s``` Right now I'm using realizableKE as turbulence model, but I also tried to run it wie kOmegaSST with the same result. I tried several things I found on the internet including:Changing mesh quality (changed it between 20.000 and 100.000 cells) Decreasing and increasing the timesteps Changing my BCs for k, epsilon and nut Used other schemes Added some extra layers to my mesh Changing the tolerance for k and epsilon Changing my relaxation factors But still my simulation looks pretty much the same, just the change of my tolerance resulted in an increase of the time that k and epsilon are calculated but still only about 1s out of 2s. Here are my current BCs for k, epsilon and nut k Code: ```boundaryField { outlet { type inletOutlet; inletValue uniform 0.001; value uniform 0.01; } symmetry { type symmetryPlane; } wall { type kqRWallFunction; value uniform 1e-06; }``` epsilon Code: ```boundaryField { outlet { type inletOutlet; inletValue uniform 0.0001; value uniform 0; } symmetry { type symmetryPlane; } wall { type epsilonWallFunction; value uniform 0.001; }``` nut Code: ```boundaryField { outlet { type calculated; value uniform 0; } symmetry { type symmetryPlane; } wall { type nutkWallFunction; value uniform 0; }``` I still think there is something with my BCs, but I dont know whats wrong or causing the problem. If anyone has an idea what I could do, please let me know. My englisch isnt the best so if you dont understand something just ask me Greets Nigirim

 November 14, 2012, 08:52 #2 Member   Join Date: Jul 2012 Posts: 60 Rep Power: 5 I got a similar problem! here: pimpleFoam: turbulence->correct(); is not executed when using residualControl Let me know when you have a solution... Thanks!

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Xabi OpenFOAM Running, Solving & CFD 3 February 25, 2014 12:24 nedved OpenFOAM Running, Solving & CFD 13 November 4, 2013 15:13 kroetenechse OpenFOAM Pre-Processing 27 August 20, 2013 13:05 sivakumar OpenFOAM Running, Solving & CFD 1 October 25, 2012 04:50 nedved OpenFOAM Running, Solving & CFD 1 November 25, 2008 21:21

All times are GMT -4. The time now is 19:01.