# kEpsilon divergence

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May 27, 2013, 09:30
kEpsilon divergence
#1
Senior Member

Join Date: Aug 2012
Posts: 229
Rep Power: 7
hi dear all,
i am analyzing the turbulent flow over a multi element airfoil, i use kEpsilon as my turbulent model, i attach another setting except the polyMesh file that have large volume in the following. i want to know why this setting give me a huge "cd and cl" value and become diverge at last???
Create time

Create mesh for time = 0

Selecting incompressible transport model Newtonian
Selecting RAS turbulence model kEpsilon
kEpsilonCoeffs
{
Cmu 0.09;
C1 1.44;
C2 1.92;
sigmaEps 1.3;
}

No field sources present

SIMPLE: convergence criteria
field p tolerance 1e-05
field U tolerance 1e-05
field "(k|epsilon|omega)" tolerance 1e-05

Starting time loop

Time = 1

DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.0851627, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 0.0620606, No Iterations 1
DICPCG: Solving for p, Initial residual = 1, Final residual = 0.00996629, No Iterations 309
time step continuity errors : sum local = 0.0145551, global = -0.000587377, cumulative = -0.000587377
DILUPBiCG: Solving for epsilon, Initial residual = 0.855568, Final residual = 0.0131864, No Iterations 2
bounding epsilon, min: -70.6847 max: 12281.4 average: 95.7268
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 0.0139852, No Iterations 2
ExecutionTime = 66.18 s ClockTime = 67 s

forceCoeffs output:
Cd = 12.5306
Cl = 8.61894
Cm = 10.947
Cl(f) = -6.63751
Cl(r) = 15.2565

forceCoeffs output:
Cd = 4.63818
Cl = 4.46189
Cm = 7.69878
Cl(f) = -5.46783
Cl(r) = 9.92972

forceCoeffs output:
Cd = 4.28411
Cl = 1.24044
Cm = 0.363232
Cl(f) = 0.256988
Cl(r) = 0.983452

Time = 2

DILUPBiCG: Solving for Ux, Initial residual = 0.371895, Final residual = 0.0219048, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.801151, Final residual = 0.0712947, No Iterations 1
DICPCG: Solving for p, Initial residual = 0.934959, Final residual = 0.00914592, No Iterations 176
time step continuity errors : sum local = 0.0844986, global = -0.00533487, cumulative = -0.00592225
DILUPBiCG: Solving for epsilon, Initial residual = 0.193973, Final residual = 0.00950288, No Iterations 1
bounding epsilon, min: -4.58686e+06 max: 2.05433e+08 average: 5828.66
DILUPBiCG: Solving for k, Initial residual = 0.800037, Final residual = 0.0154131, No Iterations 2
ExecutionTime = 99.81 s ClockTime = 100 s

forceCoeffs output:
Cd = 74.3294
Cl = 39.1365
Cm = 55.1597
Cl(f) = -35.5915
Cl(r) = 74.728

forceCoeffs output:
Cd = 29.1868
Cl = 26.3321
Cm = 46.7784
Cl(f) = -33.6123
Cl(r) = 59.9444

forceCoeffs output:
Cd = 23.8554
Cl = 5.50834
Cm = 2.1903
Cl(f) = 0.563873
Cl(r) = 4.94447

Time = 3
Warning: empty x range [2:2], adjusting to [1.98:2.02]
Warning: empty y range [-0.00592225:-0.00592225], adjusting to [-0.00598147:-0.00586303]
Warning: empty y2 range [-0.00533487:-0.00533487], adjusting to [-0.00538822:-0.00528152]
Warning: empty x range [2:2], adjusting to [1.98:2.02]

Warning: empty x range [2:2], adjusting to [1.98:2.02]
DILUPBiCG: Solving for Ux, Initial residual = 0.281258, Final residual = 0.00790785, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.309596, Final residual = 0.00740507, No Iterations 1
DICPCG: Solving for p, Initial residual = 0.809451, Final residual = 0.00786146, No Iterations 184
time step continuity errors : sum local = 0.0808879, global = -0.00575251, cumulative = -0.0116748
DILUPBiCG: Solving for epsilon, Initial residual = 0.383734, Final residual = 0.00500752, No Iterations 1
bounding epsilon, min: -2.06429e+09 max: 3.22707e+10 average: 1.25176e+06
DILUPBiCG: Solving for k, Initial residual = 0.308511, Final residual = 0.00780312, No Iterations 1
ExecutionTime = 136.12 s ClockTime = 137 s

forceCoeffs output:
Cd = 47.6661
Cl = 44.0272
Cm = 47.4463
Cl(f) = -25.4327
Cl(r) = 69.4599

forceCoeffs output:
Cd = 20.4276
Cl = 19.2879
Cm = 33.7033
Cl(f) = -24.0594
Cl(r) = 43.3473

forceCoeffs output:
Cd = 15.106
Cl = 3.52259
Cm = 1.3308
Cl(f) = 0.430496
Cl(r) = 3.0921

Time = 4

DILUPBiCG: Solving for Ux, Initial residual = 0.631827, Final residual = 0.0532422, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.287384, Final residual = 0.0218062, No Iterations 1
DICPCG: Solving for p, Initial residual = 0.0389731, Final residual = 0.000377626, No Iterations 15
time step continuity errors : sum local = 1.69174e+11, global = -0.008325, cumulative = -0.0199998
DILUPBiCG: Solving for epsilon, Initial residual = 1, Final residual = 0.0489876, No Iterations 2
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 0.0243535, No Iterations 1
ExecutionTime = 148.98 s ClockTime = 150 s

forceCoeffs output:
Cd = 5.95263e+16
Cl = 5.74333e+18
Cm = 5.28543e+18
Cl(f) = -2.41377e+18
Cl(r) = 8.1571e+18

forceCoeffs output:
Cd = 4.67148e+16
Cl = 3.5596e+18
Cm = 5.28543e+18
Cl(f) = -3.50563e+18
Cl(r) = 7.06523e+18

forceCoeffs output:
Cd = -716.963
Cl = 84.7869
Cm = -81.2341
Cl(f) = 123.628
Cl(r) = -38.8407

Time = 5

DILUPBiCG: Solving for Ux, Initial residual = 0.540127, Final residual = 0.00501485, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.685895, Final residual = 0.0146612, No Iterations 1
DICPCG: Solving for p, Initial residual = 0.00288552, Final residual = 0.00190082, No Iterations 1001
time step continuity errors : sum local = 7.55328e+12, global = -1.17074e+12, cumulative = -1.17074e+12
DILUPBiCG: Solving for epsilon, Initial residual = 0.165444, Final residual = 2.08731e-11, No Iterations 1
bounding epsilon, min: -5.08808e+31 max: 1.69734e+39 average: 1.19693e+34
DILUPBiCG: Solving for k, Initial residual = 0.824988, Final residual = 0.0704899, No Iterations 1
ExecutionTime = 296.84 s ClockTime = 300 s

forceCoeffs output:
Cd = 8.93277e+43
Cl = 1.76619e+44
Cm = 1.75932e+44
Cl(f) = -8.76223e+43
Cl(r) = 2.64242e+44

forceCoeffs output:
Cd = 7.01023e+43
Cl = 1.09465e+44
Cm = 1.75932e+44
Cl(f) = -1.212e+44
Cl(r) = 2.30664e+44

forceCoeffs output:
Cd = 3.8858e+13
Cl = 2.66218e+12
Cm = 6.69608e+12
Cl(f) = -5.365e+12
Cl(r) = 8.02717e+12

Time = 6

DILUPBiCG: Solving for Ux, Initial residual = 0.466989, Final residual = 0.0136307, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.286722, Final residual = 0.00802562, No Iterations 1
DICPCG: Solving for p, Initial residual = 0.0332657, Final residual = 0.000267814, No Iterations 3
time step continuity errors : sum local = 1.45411e+27, global = -2.89889e+11, cumulative = -1.46063e+12

thank you very much.
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