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- - **Negative value of k causing simulation to stop**
(*https://www.cfd-online.com/Forums/openfoam-solving/58458-negative-value-k-causing-simulation-stop.html*)

Hi all
I am running supersoniHi all
I am running supersonic flow along with exit back pressure condition. I am using RNGEpsilon turbulence method. I am getting the good flow development. But suddenly openfoam quits with some error. When i checked the error, only differnce i found was k is negative. This happens after flow was developed fully but not yet converged. Is there any solution to solve this problem ? Time = 0.00108087 Courant Number mean: 0.00170796 max: 0.0971893 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCG: Solving for Ux, Initial residual = 7.11502e-05, Final residual = 1.35237e-10, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.00011828, Final residual = 5.53025e-11, No Iterations 1 DILUPBiCG: Solving for h, Initial residual = 0.000251239, Final residual = 9.49742e-11, No Iterations 1 DILUPBiCG: Solving for p, Initial residual = 0.000376528, Final residual = 1.33934e-14, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 2.45546e-06, Final residual = 5.77244e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 4.80871e-08, Final residual = 6.8838e-15, No Iterations 2 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 2.13924e-12, global = 1.25215e-13, cumulative = -2.11148e-12 DILUPBiCG: Solving for p, Initial residual = 1.28753e-06, Final residual = 1.27746e-14, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 5.51159e-09, Final residual = 5.40315e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 1.26357e-09, Final residual = 2.10007e-14, No Iterations 2 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 1.15167e-11, global = -6.40266e-13, cumulative = -2.75174e-12 DILUPBiCG: Solving for epsilon, Initial residual = 6.54999e-05, Final residual = 1.64537e-10, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.000147741, Final residual = 2.10956e-10, No Iterations 1 ExecutionTime = 1.68 s ClockTime = 2 s Time = 0.00108092 Courant Number mean: 0.00177227 max: 0.0776741 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCG: Solving for Ux, Initial residual = 7.13326e-05, Final residual = 6.69864e-11, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.000120215, Final residual = 5.63942e-11, No Iterations 1 DILUPBiCG: Solving for h, Initial residual = 0.000198837, Final residual = 1.50863e-10, No Iterations 1 DILUPBiCG: Solving for p, Initial residual = 0.000254745, Final residual = 1.13091e-14, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 2.72206e-07, Final residual = 4.31035e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 7.12951e-09, Final residual = 3.73677e-15, No Iterations 2 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 1.11735e-12, global = 3.73839e-14, cumulative = -2.71436e-12 DILUPBiCG: Solving for p, Initial residual = 3.15769e-06, Final residual = 8.8416e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 8.59995e-09, Final residual = 5.96147e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 1.68437e-09, Final residual = 6.72562e-15, No Iterations 2 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 1.20992e-12, global = 1.77206e-13, cumulative = -2.53715e-12 DILUPBiCG: Solving for epsilon, Initial residual = 8.10672e-05, Final residual = 1.61564e-10, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.000190269, Final residual = 2.11132e-10, No Iterations 1 bounding k, min: -0.257568 max: 2202.59 average: 159.908 ExecutionTime = 1.76 s ClockTime = 2 s Time = 0.00108097 Courant Number mean: 0.00178108 max: 0.0838975 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCG: Solving for Ux, Initial residual = 7.17025e-05, Final residual = 7.1539e-11, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.000123248, Final residual = 5.75958e-11, No Iterations 1 DILUPBiCG: Solving for h, Initial residual = 0.000208497, Final residual = 1.2543e-10, No Iterations 1 DILUPBiCG: Solving for p, Initial residual = 0.0145355, Final residual = 8.33417e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 0.000477816, Final residual = 7.66563e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 9.7461e-05, Final residual = 8.97423e-15, No Iterations 2 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 2.62836e-12, global = 2.72003e-13, cumulative = -2.26515e-12 DILUPBiCG: Solving for p, Initial residual = 0.00632594, Final residual = 8.8338e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 6.28529e-05, Final residual = 8.58555e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 1.99815e-07, Final residual = 2.34281e-14, No Iterations 2 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 8.98943e-12, global = 2.80106e-13, cumulative = -1.98504e-12 DILUPBiCG: Solving for epsilon, Initial residual = 0.00343727, Final residual = 1.58363e-10, No Iterations 1 bounding epsilon, min: -12607.9 max: 4.37996e+07 average: 618204 DILUPBiCG: Solving for k, Initial residual = 0.00864829, Final residual = 2.08733e-10, No Iterations 1 ExecutionTime = 1.86 s ClockTime = 2 s Time = 0.00108102 Courant Number mean: 0.0018193 max: 0.872636 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCG: Solving for Ux, Initial residual = 0.000284262, Final residual = 6.7951e-11, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.0015673, Final residual = 6.46087e-11, No Iterations 1 DILUPBiCG: Solving for h, Initial residual = 0.00829178, Final residual = 4.08737e-10, No Iterations 1 DILUPBiCG: Solving for p, Initial residual = 0.0170355, Final residual = 7.43462e-15, No Iterations 3 DILUPBiCG: Solving for p, Initial residual = 0.000160206, Final residual = 6.32461e-15, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 2.24195e-08, Final residual = 5.34237e-15, No Iterations 2 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 1.9573e-12, global = -2.59168e-13, cumulative = -2.24421e-12 DILUPBiCG: Solving for p, Initial residual = 6.45607e-06, Final residual = 2.06521e-14, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 8.2883e-09, Final residual = 6.84259e-14, No Iterations 2 DILUPBiCG: Solving for p, Initial residual = 1.18195e-09, Final residual = 5.45102e-15, No Iterations 2 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 1.88121e-12, global = 1.1234e-13, cumulative = -2.13187e-12 DILUPBiCG: Solving for epsilon, Initial residual = 0.000681664, Final residual = 1.63971e-10, No Iterations 1 bounding epsilon, min: -399912 max: 4.37998e+07 average: 619573 DILUPBiCG: Solving for k, Initial residual = 0.00185613, Final residual = 2.23178e-10, No Iterations 1 bounding k, min: -198.053 max: 4258.97 average: 161.253 ExecutionTime = 1.94 s ClockTime = 2 s Time = 0.00108107 Courant Number mean: 0.00184301 max: 0.170472 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCG: Solving for Ux, Initial residual = 0.000111599, Final residual = 6.88509e-11, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 0.000439034, Final residual = 6.90532e-11, No Iterations 1 DILUPBiCG: Solving for h, Initial residual = 0.00458797, Final residual = 5.4244e-10, No Iterations 1 Maximum number of iterations exceeded#0 Foam::error::printStack(Foam:http://www.cfd-online.com/OpenFOAM_D...part/proud.gifstream&) in "/home/vc/OpenFOAM/OpenFOAM-1.5/lib/linuxGccDPOpt/libOpenFOAM.so" #1 Foam::error::abort() in "/home/vc/OpenFOAM/OpenFOAM-1.5/lib/linuxGccDPOpt/libOpenFOAM.so" #2 Foam::hThermo<foam::puremixture<foam::consttranspo rt<foam::speciethermo<foam::hc onstthermo<foam::perfectgas> > > > >::calculate() in "/home/vc/OpenFOAM/OpenFOAM-1.5/lib/linuxGccDPOpt/libbasicThermophysicalModels.s o" #3 Foam::hThermo<foam::puremixture<foam::consttranspo rt<foam::speciethermo<foam::hc onstthermo<foam::perfectgas> > > > >::correct() in "/home/vc/OpenFOAM/OpenFOAM-1.5/lib/linuxGccDPOpt/libbasicThermophysicalModels.s o" #4 main in "/home/vc/OpenFOAM/OpenFOAM-1.5/applications/bin/linuxGccDPOpt/sonicTurbFoam" #5 __libc_start_main in "/lib/libc.so.6" #6 Foam::regIOobject::readIfModified() in "/home/vc/OpenFOAM/OpenFOAM-1.5/applications/bin/linuxGccDPOpt/sonicTurbFoam" From function specieThermo<thermo>::T(scalar f, scalar T0, scalar (specieThermo<thermo>::*F)(const scalar) const, scalar (specieThermo<thermo>::*dFdT)(const scalar) const) const in file /home/vc/OpenFOAM/OpenFOAM-1.5/src/thermophysicalModels/specie/lnInclude/specieT hermoI.H at line 78. FOAM aborting Abort |

Your simulation has blown up aYour simulation has blown up a while before - have a look at your turbulence levels.
What you need to do is to adjust the discretisation on the k and epsilon. FOr starters, use upwind on convection terms, and add some Gauss linear limited 0.5 on diffusion for convection and diffusion. This should fix it - good luck! Hrv |

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