pisoFoam with k-epsilon turb blows up - Some questions

Heroic · December 10, 2012, 09:47

Hello,

I have been working on the mesh in order to get rid of the non-orthogonal elements. Right now I only have bottom up generated tetra mesh (no prism layers), but that should hold to at least get everything up and running if I am not mistaken.

The quality of the mesh should be good. In ICEM, the lowest quality is something around 0.22. However, upon performing a mesh check using checkMesh -allTopology -allGeometry, I get a failed check on the determinants

Also, I am still trying to find a way to get the fixed outlet velocity working. Any advice on this is, still, greatly appreciated.

Kind regards.

Code:

Checking geometry...
    Overall domain bounding box (-12 -9.25668e-06 -0.267927) (6.94232 8.58 7.74)
    Mesh (non-empty, non-wedge) directions (1 1 1)
    Mesh (non-empty) directions (1 1 1)
    Boundary openness (-3.79415e-17 -2.46278e-16 3.39898e-16) OK.
    Max cell openness = 2.96999e-16 OK.
    Max aspect ratio = 7.49919 OK.
    Minumum face area = 9.23367e-06. Maximum face area = 0.264079.  Face area magnitudes OK.
    Min volume = 2.48245e-08. Max volume = 0.0409205.  Total volume = 1220.37.  Cell volumes OK.
    Mesh non-orthogonality Max: 62.5417 average: 16.4373
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.920117 OK.
    Coupled point location match (average 0) OK.
    Face tets OK.
    Min/max edge length = 0.00337765 0.890872 OK.
    All angles in faces OK.
    All face flatness OK.
    Cell determinant (wellposedness) : minimum: 0 average: 1.60163
 ***Cells with small determinant found, number of cells: 2167
  <<Writing 2167 under-determined cells to set underdeterminedCells
    Concave cell check OK.

Failed 1 mesh checks.

End

yzf1215 · December 10, 2012, 09:50

***Cells with small determinant found, number of cells: 2167
You should check this in ICEM and fix them

Heroic · December 10, 2012, 11:55

That is what I have done already. The quality is at least 0.2 for all tetras. If I check for determinant only, it even says the determinant is 1 everywhere. However, the % behind it less than 100%, I am curious what's up with the remaining 8%... (see attachments)

Heroic · December 13, 2012, 03:44

It seems I got things up and running now, including the k-epsilon model. Due to some high velocities through small cells I seem to be getting very high (bounded) values for epsilon locally. These are of the size 1e5 and for some reason they do not appear for every timestep, but only every now and then. Even more weird is that these bounded epsilon also show a decreasing behavior from time to time and k is rarely bounded.

Upon checking the results in paraview, the high values are always there, even if there is no reported bounding epsilon in the log file. I have terminated my simulation for now and I am going to discuss this behavior with a colleague of mine.

It would be nice to hear some opinions on this from others with more knowledge on this subject as well. Please see the attached picture and fragment of my log file. Keeping in mind that I am actually reaching good convergence, would it be wise to continue on this simulation or is it better to start over and find a way to totally eliminate the bounded variables? Is there a way to keep going with the current simulation and eliminate this behavior?

Code:

Courant Number mean: 9.55372e-05 max: 0.219991
Time = 0.13315

diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 6.73373e-07, Final residual = 3.20221e-11, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 2.22739e-06, Final residual = 1.4288e-10, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 1.30619e-05, Final residual = 6.47912e-10, No Iterations 1
DILUPBiCG:  Solving for alpha1, Initial residual = 8.6486e-08, Final residual = 8.6486e-08, No Iterations 0
Solid phase fraction = 4.71282e-06  Min(alpha1) = 0  Max(alpha1) = 0.4
GAMG:  Solving for p_rgh, Initial residual = 0.000202456, Final residual = 1.80145e-07, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 2.70531e-05, Final residual = 2.34654e-08, No Iterations 6
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 6.42526e-14, global = -3.46809e-15, cumulative = -4.2928e-11
GAMG:  Solving for p_rgh, Initial residual = 4.09015e-06, Final residual = 2.69331e-09, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 6.81026e-07, Final residual = 6.59748e-10, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.7721e-14, global = -4.55999e-15, cumulative = -4.29325e-11
GAMG:  Solving for p_rgh, Initial residual = 1.44307e-07, Final residual = 1.03114e-10, No Iterations 7
GAMG:  Solving for p_rgh, Initial residual = 4.03171e-08, Final residual = 3.46799e-11, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.59999e-14, global = -4.04968e-15, cumulative = -4.29366e-11
GAMG:  Solving for p_rgh, Initial residual = 1.17086e-08, Final residual = 6.23799e-12, No Iterations 8
GAMG:  Solving for p_rgh, Initial residual = 9.4489e-09, Final residual = 9.74704e-13, No Iterations 8
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.43245e-14, global = -4.13848e-15, cumulative = -4.29407e-11
DILUPBiCG:  Solving for epsilon, Initial residual = 2.65759e-07, Final residual = 1.47193e-11, No Iterations 1
bounding epsilon, min: -0.00553507 max: 103118 average: 39.5082
DILUPBiCG:  Solving for k, Initial residual = 1.35119e-06, Final residual = 5.30976e-10, No Iterations 1
ExecutionTime = 63036.2 s  ClockTime = 64522 s

... Some timesteps without bounding epsilon follow. I had to cut them off to stay within the max character limit ...

Courant Number mean: 9.55379e-05 max: 0.220011
Time = 0.13325

diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 6.73169e-07, Final residual = 3.24129e-11, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 2.22689e-06, Final residual = 1.43334e-10, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 1.30599e-05, Final residual = 6.52675e-10, No Iterations 1
DILUPBiCG:  Solving for alpha1, Initial residual = 8.64956e-08, Final residual = 8.64956e-08, No Iterations 0
Solid phase fraction = 4.71282e-06  Min(alpha1) = 0  Max(alpha1) = 0.4
GAMG:  Solving for p_rgh, Initial residual = 0.000201444, Final residual = 1.60844e-07, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 2.61183e-05, Final residual = 9.24127e-09, No Iterations 7
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 5.61681e-14, global = -2.98193e-15, cumulative = -4.30777e-11
GAMG:  Solving for p_rgh, Initial residual = 3.86619e-06, Final residual = 2.34723e-09, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 6.35014e-07, Final residual = 4.72341e-10, No Iterations 6
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.67156e-14, global = -3.68224e-15, cumulative = -4.30814e-11
GAMG:  Solving for p_rgh, Initial residual = 1.34363e-07, Final residual = 8.48447e-11, No Iterations 7
GAMG:  Solving for p_rgh, Initial residual = 3.58766e-08, Final residual = 2.88988e-11, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.59304e-14, global = -3.55608e-15, cumulative = -4.30849e-11
GAMG:  Solving for p_rgh, Initial residual = 1.06668e-08, Final residual = 5.16055e-12, No Iterations 8
GAMG:  Solving for p_rgh, Initial residual = 8.27392e-09, Final residual = 8.58417e-13, No Iterations 8
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.31626e-14, global = -3.55087e-15, cumulative = -4.30885e-11
DILUPBiCG:  Solving for epsilon, Initial residual = 2.65268e-07, Final residual = 1.45611e-11, No Iterations 1
DILUPBiCG:  Solving for k, Initial residual = 1.3485e-06, Final residual = 5.63431e-10, No Iterations 1
ExecutionTime = 63230.5 s  ClockTime = 64720 s

Courant Number mean: 9.5538e-05 max: 0.220013
Time = 0.13326

diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 6.73155e-07, Final residual = 3.24443e-11, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 2.22686e-06, Final residual = 1.43377e-10, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 1.30598e-05, Final residual = 6.53214e-10, No Iterations 1
DILUPBiCG:  Solving for alpha1, Initial residual = 8.64965e-08, Final residual = 8.64965e-08, No Iterations 0
Solid phase fraction = 4.71282e-06  Min(alpha1) = 0  Max(alpha1) = 0.4
GAMG:  Solving for p_rgh, Initial residual = 0.000206822, Final residual = 1.82456e-07, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 2.9564e-05, Final residual = 1.68898e-08, No Iterations 7
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 6.30398e-14, global = -3.45633e-15, cumulative = -4.30919e-11
GAMG:  Solving for p_rgh, Initial residual = 4.34841e-06, Final residual = 3.49822e-09, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 7.17663e-07, Final residual = 4.03597e-10, No Iterations 7
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.85699e-14, global = -4.27903e-15, cumulative = -4.30962e-11
GAMG:  Solving for p_rgh, Initial residual = 1.53179e-07, Final residual = 1.33318e-10, No Iterations 7
GAMG:  Solving for p_rgh, Initial residual = 4.03591e-08, Final residual = 3.8995e-11, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.77545e-14, global = -3.73605e-15, cumulative = -4.31e-11
GAMG:  Solving for p_rgh, Initial residual = 1.16859e-08, Final residual = 5.82896e-12, No Iterations 8
GAMG:  Solving for p_rgh, Initial residual = 9.22654e-09, Final residual = 5.36028e-13, No Iterations 9
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.40814e-14, global = -3.61683e-15, cumulative = -4.31036e-11
DILUPBiCG:  Solving for epsilon, Initial residual = 2.6522e-07, Final residual = 1.45454e-11, No Iterations 1
bounding epsilon, min: -0.0146594 max: 103133 average: 39.5529
DILUPBiCG:  Solving for k, Initial residual = 1.34824e-06, Final residual = 5.6666e-10, No Iterations 1
ExecutionTime = 63252.2 s  ClockTime = 64743 s

Courant Number mean: 9.55381e-05 max: 0.220015
Time = 0.13327

diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 6.73124e-07, Final residual = 3.24828e-11, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 2.22681e-06, Final residual = 1.43556e-10, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 1.30595e-05, Final residual = 6.53373e-10, No Iterations 1
DILUPBiCG:  Solving for alpha1, Initial residual = 8.64974e-08, Final residual = 8.64974e-08, No Iterations 0
Solid phase fraction = 4.71282e-06  Min(alpha1) = 0  Max(alpha1) = 0.4
GAMG:  Solving for p_rgh, Initial residual = 0.00020463, Final residual = 1.80884e-07, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 2.84468e-05, Final residual = 1.89107e-08, No Iterations 7
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 6.12578e-14, global = -3.17955e-15, cumulative = -4.31067e-11
GAMG:  Solving for p_rgh, Initial residual = 4.26351e-06, Final residual = 3.66951e-09, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 7.33175e-07, Final residual = 5.91502e-10, No Iterations 6
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.61081e-14, global = -4.4349e-15, cumulative = -4.31112e-11
GAMG:  Solving for p_rgh, Initial residual = 1.55993e-07, Final residual = 6.94e-11, No Iterations 8
GAMG:  Solving for p_rgh, Initial residual = 4.29368e-08, Final residual = 3.61959e-11, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.54608e-14, global = -3.98236e-15, cumulative = -4.31152e-11
GAMG:  Solving for p_rgh, Initial residual = 1.19962e-08, Final residual = 6.20707e-12, No Iterations 8
GAMG:  Solving for p_rgh, Initial residual = 9.62159e-09, Final residual = 5.64534e-13, No Iterations 9
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.27451e-14, global = -3.89695e-15, cumulative = -4.31191e-11
DILUPBiCG:  Solving for epsilon, Initial residual = 2.65171e-07, Final residual = 1.45298e-11, No Iterations 1
DILUPBiCG:  Solving for k, Initial residual = 1.34797e-06, Final residual = 5.70079e-10, No Iterations 1
ExecutionTime = 63272 s  ClockTime = 64764 s

Courant Number mean: 9.55381e-05 max: 0.220017
Time = 0.13328

diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 6.73101e-07, Final residual = 3.25277e-11, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 2.22672e-06, Final residual = 1.43649e-10, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 1.30592e-05, Final residual = 6.53624e-10, No Iterations 1
DILUPBiCG:  Solving for alpha1, Initial residual = 8.64984e-08, Final residual = 8.64984e-08, No Iterations 0
Solid phase fraction = 4.71282e-06  Min(alpha1) = 0  Max(alpha1) = 0.4
GAMG:  Solving for p_rgh, Initial residual = 0.000199448, Final residual = 1.54254e-07, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 2.50483e-05, Final residual = 1.89519e-08, No Iterations 6
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 6.20065e-14, global = -3.52836e-15, cumulative = -4.31226e-11
GAMG:  Solving for p_rgh, Initial residual = 3.64174e-06, Final residual = 2.16334e-09, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 6.05503e-07, Final residual = 2.69169e-10, No Iterations 7
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.72243e-14, global = -4.49821e-15, cumulative = -4.31271e-11
GAMG:  Solving for p_rgh, Initial residual = 1.28108e-07, Final residual = 8.60518e-11, No Iterations 7
GAMG:  Solving for p_rgh, Initial residual = 3.53406e-08, Final residual = 2.89977e-11, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.67016e-14, global = -4.02559e-15, cumulative = -4.31311e-11
GAMG:  Solving for p_rgh, Initial residual = 1.03696e-08, Final residual = 6.77484e-12, No Iterations 8
GAMG:  Solving for p_rgh, Initial residual = 9.30403e-09, Final residual = 5.6405e-13, No Iterations 9
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.33453e-14, global = -3.93433e-15, cumulative = -4.3135e-11
DILUPBiCG:  Solving for epsilon, Initial residual = 2.65122e-07, Final residual = 1.45141e-11, No Iterations 1
DILUPBiCG:  Solving for k, Initial residual = 1.3477e-06, Final residual = 5.73409e-10, No Iterations 1
ExecutionTime = 63293.2 s  ClockTime = 64786 s

Courant Number mean: 9.55382e-05 max: 0.220019
Time = 0.13329

diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 6.73085e-07, Final residual = 3.25652e-11, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 2.22669e-06, Final residual = 1.43745e-10, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 1.3059e-05, Final residual = 6.53576e-10, No Iterations 1
DILUPBiCG:  Solving for alpha1, Initial residual = 8.64994e-08, Final residual = 8.64994e-08, No Iterations 0
Solid phase fraction = 4.71282e-06  Min(alpha1) = 0  Max(alpha1) = 0.4
GAMG:  Solving for p_rgh, Initial residual = 0.000203005, Final residual = 1.79916e-07, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 2.68167e-05, Final residual = 2.67205e-08, No Iterations 6
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 6.5267e-14, global = -3.79928e-15, cumulative = -4.31388e-11
GAMG:  Solving for p_rgh, Initial residual = 3.97084e-06, Final residual = 2.6292e-09, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 6.54607e-07, Final residual = 6.21318e-10, No Iterations 6
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.91615e-14, global = -4.95388e-15, cumulative = -4.31438e-11
GAMG:  Solving for p_rgh, Initial residual = 1.37601e-07, Final residual = 9.80408e-11, No Iterations 7
GAMG:  Solving for p_rgh, Initial residual = 3.82828e-08, Final residual = 2.98687e-11, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.58331e-14, global = -4.6095e-15, cumulative = -4.31484e-11
GAMG:  Solving for p_rgh, Initial residual = 1.08881e-08, Final residual = 7.40095e-12, No Iterations 8
GAMG:  Solving for p_rgh, Initial residual = 1.00421e-08, Final residual = 8.25128e-13, No Iterations 8
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.31451e-14, global = -4.21148e-15, cumulative = -4.31526e-11
DILUPBiCG:  Solving for epsilon, Initial residual = 2.65074e-07, Final residual = 1.44984e-11, No Iterations 1
DILUPBiCG:  Solving for k, Initial residual = 1.34743e-06, Final residual = 5.76752e-10, No Iterations 1
ExecutionTime = 63313.1 s  ClockTime = 64807 s

Courant Number mean: 9.55383e-05 max: 0.220021
Time = 0.1333

diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG:  Solving for Ux, Initial residual = 6.73067e-07, Final residual = 3.25873e-11, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 2.22662e-06, Final residual = 1.4377e-10, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 1.30587e-05, Final residual = 6.53616e-10, No Iterations 1
DILUPBiCG:  Solving for alpha1, Initial residual = 8.65003e-08, Final residual = 8.65003e-08, No Iterations 0
Solid phase fraction = 4.71282e-06  Min(alpha1) = 0  Max(alpha1) = 0.4
GAMG:  Solving for p_rgh, Initial residual = 0.000203332, Final residual = 1.55745e-07, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 2.68662e-05, Final residual = 2.01764e-08, No Iterations 7
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 6.53667e-14, global = -4.25321e-15, cumulative = -4.31569e-11
GAMG:  Solving for p_rgh, Initial residual = 3.94813e-06, Final residual = 2.79355e-09, No Iterations 5
GAMG:  Solving for p_rgh, Initial residual = 6.43015e-07, Final residual = 2.92496e-10, No Iterations 7
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.86857e-14, global = -4.21542e-15, cumulative = -4.31611e-11
GAMG:  Solving for p_rgh, Initial residual = 1.36678e-07, Final residual = 9.05711e-11, No Iterations 7
GAMG:  Solving for p_rgh, Initial residual = 3.68273e-08, Final residual = 2.84291e-11, No Iterations 5
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.78365e-14, global = -4.25555e-15, cumulative = -4.31653e-11
GAMG:  Solving for p_rgh, Initial residual = 1.08069e-08, Final residual = 6.99844e-12, No Iterations 8
GAMG:  Solving for p_rgh, Initial residual = 9.87503e-09, Final residual = 7.91717e-13, No Iterations 8
diagonal:  Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 3.48573e-14, global = -4.24741e-15, cumulative = -4.31696e-11
DILUPBiCG:  Solving for epsilon, Initial residual = 2.65025e-07, Final residual = 1.44828e-11, No Iterations 1
DILUPBiCG:  Solving for k, Initial residual = 1.34717e-06, Final residual = 5.80109e-10, No Iterations 1
ExecutionTime = 63335.1 s  ClockTime = 64831 s

Aadhavan · December 13, 2012, 11:50

Hi Heroic,
I hope you know that bounding is an indignation of the corresponding values are not in the limit.
you can fix this changing your epsilon scheme in system folder.
which scheme you are using for epsilon, try to use upwind scheme then it will be fine.
I think after some reasonable time step you can change your schemes.

thanks,
Aadhavan

Heroic · December 17, 2012, 03:04

Hi Aadhavan,

For k and epsilon I am using upwind schemes as you stated. In contrast to the values I had before, I found out I had to increase the values outside of the pipe by a lot in order to increase the stability. I am aware of the fact I bounded variables are there in order to prevent the system from blowing up while actually not being correct variables.

It seems strange to me that even k and epsilon still reach convergence though. Same goes for the fact that only 1 out of 5-10 timesteps is bounded, while the others are not. Any idea what the reason could be for this?

Kind regards.

Aadhavan · December 17, 2012, 04:34

Hi Heroic,
Gut, if you didnt get bounding error after some time step then its fine, you no need to worry about it, simply go ahead.

Thanks,
Aadhavan

December 13, 2012, 11:50		#25
Aadhavan Member Aathavan Join Date: Nov 2012 Posts: 70 Rep Power: 14	Hi Heroic, I hope you know that bounding is an indignation of the corresponding values are not in the limit. you can fix this changing your epsilon scheme in system folder. which scheme you are using for epsilon, try to use upwind scheme then it will be fine. I think after some reasonable time step you can change your schemes. thanks, Aadhavan Last edited by Aadhavan; December 15, 2012 at 09:10.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
SimpleFoam k and epsilon bounded	nedved	OpenFOAM Running, Solving & CFD	16	March 4, 2017 09:30
epsilon and K blowing up.	sivakumar	OpenFOAM Running, Solving & CFD	1	October 25, 2012 05:50
k epsilon boundary conditions for pisofoam ras solver	chamoun	OpenFOAM	4	May 10, 2011 06:30
Compressible epsilon blows up	swahono	OpenFOAM	10	November 26, 2010 06:38
SimpleFoam k and epsilon bounded	nedved	OpenFOAM Running, Solving & CFD	1	November 25, 2008 21:21

December 10, 2012, 09:50		#22
yzf1215 Member Zifei Yin Join Date: Sep 2012 Location: Shanghai & Ames Posts: 33 Rep Power: 14	***Cells with small determinant found, number of cells: 2167 You should check this in ICEM and fix them

December 17, 2012, 03:04		#26
Heroic New Member B Join Date: Oct 2012 Posts: 17 Rep Power: 14	Hi Aadhavan, For k and epsilon I am using upwind schemes as you stated. In contrast to the values I had before, I found out I had to increase the values outside of the pipe by a lot in order to increase the stability. I am aware of the fact I bounded variables are there in order to prevent the system from blowing up while actually not being correct variables. It seems strange to me that even k and epsilon still reach convergence though. Same goes for the fact that only 1 out of 5-10 timesteps is bounded, while the others are not. Any idea what the reason could be for this? Kind regards.

December 17, 2012, 04:34		#27
Aadhavan Member Aathavan Join Date: Nov 2012 Posts: 70 Rep Power: 14	Hi Heroic, Gut, if you didnt get bounding error after some time step then its fine, you no need to worry about it, simply go ahead. Thanks, Aadhavan