CFD Online Discussion Forums - SimpleFoam k and epsilon bounded

Hello everyone.

I have been working on the nlf-0414 laminar airfoil. I have calculated the drag and lift coefficients for various angles and have got decent results. I have been using the steady state solver - simpleFoam - for unstructured grids. My simulations are two-dimensional.

I am now working on an ice accreted nlf-0414 airfoil. I am using the same solver settings as the non-ice nlf-0414 airfoil but my solution blows up after a few iterations. Here are some details about the case:

I created the mesh in ICEMCFD. I converted it into a fluent mesh which i then converted into foam format using fluent3dMeshTofoam.

As the case is 2D, i am using empty boundaries on the left and right sides of the domain. I am using inlet and outlet boundaries and walls for the airfoil, top and bottom regions.

I am using the k-epsilon turbulence model. I estimated k to be 20.23 and epsilon to be 166.12. I used these same settings for the non-ice cases which converged fine. My Reynolds number based on airfoil chord (0.914m) is 4.6x10^6 and inlet velocity is 73.45m/s.

I am attaching my case file:

nlf-0414 case

When i run my case this is the problem i am having:

Create time

Create mesh for time = 0

Reading field p

Reading field U

Reading/calculating face flux field phi

Selecting incompressible transport model Newtonian
Selecting RAS turbulence model kEpsilon
kEpsilonCoeffs
{
Cmu 0.09;
C1 1.44;
C2 1.92;
alphaEps 0.76923;
}

Starting time loop

Time = 1

DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.0868802, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 0.0384705, No Iterations 1
ICE default IO error handler doing an exit(), pid = 25139, errno = 0
DICPCG: Solving for p, Initial residual = 1, Final residual = 0.000974596, No Iterations 453
time step continuity errors : sum local = 0.0443247, global = -0.000256781, cumulative = -0.000256781
DILUPBiCG: Solving for epsilon, Initial residual = 0.177983, Final residual = 0.0134905, No Iterations 1
bounding epsilon, min: -5124.54 max: 2.59707e+06 average: 23725.9
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 0.0221967, No Iterations 1
ExecutionTime = 75.45 s ClockTime = 77 s

Time = 2

DILUPBiCG: Solving for Ux, Initial residual = 0.00022456, Final residual = 1.72182e-07, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.171213, Final residual = 6.76872e-06, No Iterations 1
DICPCG: Solving for p, Initial residual = 0.199818, Final residual = 0.00173239, No Iterations 1001
time step continuity errors : sum local = 0.25953, global = 0.000524615, cumulative = 0.000267833
DILUPBiCG: Solving for epsilon, Initial residual = 0.380199, Final residual = 3.54249e-13, No Iterations 1
bounding epsilon, min: -62.2232 max: 6.84878e+06 average: 26467.3
DILUPBiCG: Solving for k, Initial residual = 0.00031994, Final residual = 5.93409e-06, No Iterations 1
ExecutionTime = 211.38 s ClockTime = 223 s

Time = 3

DILUPBiCG: Solving for Ux, Initial residual = 0.999831, Final residual = 0.0334756, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 0.999976, Final residual = 0.0290285, No Iterations 2
DICPCG: Solving for p, Initial residual = 0.783759, Final residual = 0.000762911, No Iterations 635
time step continuity errors : sum local = 5126.09, global = -115.949, cumulative = -115.949
DILUPBiCG: Solving for epsilon, Initial residual = 1, Final residual = 0.0740209, No Iterations 2
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 0.000545361, No Iterations 1
ExecutionTime = 304.56 s ClockTime = 319 s

Time = 4

DILUPBiCG: Solving for Ux, Initial residual = 0.637303, Final residual = 0.0534082, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.392361, Final residual = 0.000317455, No Iterations 2
DICPCG: Solving for p, Initial residual = 0.949414, Final residual = 0.00213447, No Iterations 1001
time step continuity errors : sum local = 4384.93, global = -1118.18, cumulative = -1234.13
DILUPBiCG: Solving for epsilon, Initial residual = 0.255896, Final residual = 0.0139967, No Iterations 1
bounding epsilon, min: -1.31507e+11 max: 2.87675e+27 average: 9.48764e+21
DILUPBiCG: Solving for k, Initial residual = 0.999977, Final residual = 0.092381, No Iterations 1
ExecutionTime = 441.92 s ClockTime = 466 s

Time = 5

DILUPBiCG: Solving for Ux, Initial residual = 0.565411, Final residual = 0.000464199, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.361508, Final residual = 0.000488244, No Iterations 1
DICPCG: Solving for p, Initial residual = 5.22619e-06, Final residual = 1.98698e-08, No Iterations 1
time step continuity errors : sum local = 1.87592e+10, global = -390.727, cumulative = -1624.85
DILUPBiCG: Solving for epsilon, Initial residual = 0.178086, Final residual = 0.0001416, No Iterations 1
bounding epsilon, min: -3.05682e+26 max: 2.8755e+33 average: 5.0373e+27
DILUPBiCG: Solving for k, Initial residual = 0.0246705, Final residual = 0.000480176, No Iterations 1
bounding k, min: -341683 max: 5.29681e+24 average: 2.90027e+19
ExecutionTime = 452.27 s ClockTime = 477 s

Time = 6

DILUPBiCG: Solving for Ux, Initial residual = 0.00134352, Final residual = 1.02079e-05, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.0010846, Final residual = 5.96071e-06, No Iterations 1
DICPCG: Solving for p, Initial residual = 3.86649e-06, Final residual = 8.28192e-08, No Iterations 3
time step continuity errors : sum local = 1.84347e+19, global = 11386.1, cumulative = 9761.24
DILUPBiCG: Solving for epsilon, Initial residual = 2.93311e-10, Final residual = 2.93311e-10, No Iterations 0
DILUPBiCG: Solving for k, Initial residual = 0.114498, Final residual = 0.00215299, No Iterations 1
bounding k, min: -332156 max: 1.09647e+40 average: 8.20484e+34
ExecutionTime = 462.33 s ClockTime = 488 s

Time = 7

DILUPBiCG: Solving for Ux, Initial residual = 0.0498993, Final residual = 0.000172662, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.0784033, Final residual = 0.000290499, No Iterations 1
DICPCG: Solving for p, Initial residual = 2.31156e-23, Final residual = 2.31156e-23, No Iterations 0
time step continuity errors : sum local = 1.52759e+30, global = 1.7678e+14, cumulative = 1.7678e+14
DILUPBiCG: Solving for epsilon, Initial residual = 0.197579, Final residual = 0.00838687, No Iterations 1
bounding epsilon, min: -7.90723e+56 max: 8.65931e+63 average: 4.08564e+58
DILUPBiCG: Solving for k, Initial residual = 0.999368, Final residual = 0.0632189, No Iterations 1
bounding k, min: -4.54562e+29 max: 1.42308e+47 average: 1.79576e+42
ExecutionTime = 471.52 s ClockTime = 500 s

Time = 8

DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 7.10734e-08, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.646717, Final residual = 9.62027e-09, No Iterations 1
DICPCG: Solving for p, Initial residual = 4.36332e-21, Final residual = 4.36332e-21, No Iterations 0
time step continuity errors : sum local = 1.27322e+32, global = 8.48049e+15, cumulative = 8.65727e+15
DILUPBiCG: Solving for epsilon, Initial residual = 0.997213, Final residual = 2.00069e-08, No Iterations 1
bounding epsilon, min: -1.51347e+71 max: 1.90819e+89 average: 7.36319e+83
DILUPBiCG: Solving for k, Initial residual = 0.203853, Final residual = 7.00189e-08, No Iterations 1
bounding k, min: -9.21274e+43 max: 3.56366e+57 average: 1.11523e+52
ExecutionTime = 480.72 s ClockTime = 509 s

Time = 9

DILUPBiCG: Solving for Ux, Initial residual = 4.80891e-09, Final residual = 4.80891e-09, No Iterations 0
DILUPBiCG: Solving for Uy, Initial residual = 4.77966e-09, Final residual = 4.77966e-09, No Iterations 0
DICPCG: Solving for p, Initial residual = 1.15667e-20, Final residual = 1.15667e-20, No Iterations 0
time step continuity errors : sum local = 2.88697e+32, global = 1.34591e+17, cumulative = 1.43248e+17
DILUPBiCG: Solving for epsilon, Initial residual = 9.2793e-12, Final residual = 9.2793e-12, No Iterations 0
bounding epsilon, min: 4.97127e-19 max: 1.90819e+89 average: 7.36319e+83
DILUPBiCG: Solving for k, Initial residual = 2.00211e-06, Final residual = 2.97586e-13, No Iterations 1
bounding k, min: -6.9942e+51 max: 1.64917e+75 average: 4.51736e+69
ExecutionTime = 490.87 s ClockTime = 521 s

Time = 10

DILUPBiCG: Solving for Ux, Initial residual = 4.50988e-06, Final residual = 3.0425e-07, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 2.41985e-05, Final residual = 1.47112e-06, No Iterations 1
DICPCG: Solving for p, Initial residual = 3.28653e-20, Final residual = 3.28653e-20, No Iterations 0
time step continuity errors : sum local = 5.24766e+32, global = -6.73284e+15, cumulative = 1.36515e+17
DILUPBiCG: Solving for epsilon, Initial residual = 7.52866e-30, Final residual = 7.52866e-30, No Iterations 0
DILUPBiCG: Solving for k, Initial residual = 3.68813e-06, Final residual = 1.75885e-07, No Iterations 1
bounding k, min: -6.74138e+68 max: 1.08664e+75 average: 2.03979e+70
ExecutionTime = 500.85 s ClockTime = 533 s

K and epsilon keep on being bounded which causes the case to diverge. I have tried to adjust the inlet values of k and epsilon but nothing changes. I have looked through the forum for similar problems but still cannot fix my problem. I would be very greatful for any suggestions to improve my case.

Also, to change from the k-epsilon to spalartallmaras turbulence model, what changes do i have to make in my case?