[sandrobrad]

HI buddies, I would like to ask you something but first let me give u context.

I am a newbie using OPENFOAM. I've done a simulation of a flow on naca0012 using the spalartAllmaras turbulence modeland given an specific boundary conditions(I'm gonna attach all my case) . The results was quite good. However,I want to simulate that airfoil using the komegaSST. Embrace urselves cause I am going to ask you some questions:
1) How can i calculate the boundary conditions and wall conditions for omega and k ? I mean, i would like to know which certain of formulas are appropiated for AN AIRFOIL. I've emphasized that bc I come across a lot of formulas that involves turbulence lenght scale, initial turbulence intensity and I don't know if that values are dependent on the geometry or the flow behaviour.
2) As a consequence of not knowing the boundary conditions , I tried with the BC of one OPENFOAM'S tutorial.Eventually , i got this message and I dont know where I can start.

smoothSolver:  Solving for Ux, Initial residual = 0.396356, Final residual = 0.0210701, No Iterations 36
smoothSolver:  Solving for Uy, Initial residual = 0.443888, Final residual = 0.0349726, No Iterations 22
GAMG:  Solving for p, Initial residual = 1, Final residual = 0.0829205, No Iterations 5
time step continuity errors : sum local = 4.0495e+18, global = -5.2526e+13, cumulative = -5.25259e+13
smoothSolver:  Solving for omega, Initial residual = 0.442589, Final residual = 2.4382e-05, No Iterations 1
bounding omega, min: -1.04133e+20 max: 1.32147e+26 average: 1.65136e+21
smoothSolver:  Solving for k, Initial residual = 0.276971, Final residual = 0.00730411, No Iterations 2
bounding k, min: -107872 max: 611891 average: 239.716
ExecutionTime = 7.62 s  ClockTime = 8 s

forceCoeffs forceCoeffs1 execute:
    Coefficients
        Cd       : -8.50109e+32    (pressure: -8.50109e+32    viscous: 5.10581e+22)
        Cs       : 2.30614e+14    (pressure: 2.73881e+14    viscous: -4.32663e+13)
        Cl       : 4.16906e+32    (pressure: 4.16906e+32    viscous: -1.91343e+24)
        CmRoll       : -6.25359e+31    (pressure: -6.25359e+31    viscous: 2.87014e+23)
        CmPitch       : 2.92373e+32    (pressure: 2.92373e+32    viscous: -1.37348e+24)
        CmYaw       : -1.27516e+32    (pressure: -1.27516e+32    viscous: 7.65872e+21)
        Cd(f)    : -4.8759e+32
        Cd(r)    : -3.62518e+32
        Cs(f)    : -1.27516e+32
        Cs(r)    : 1.27516e+32
        Cl(f)    : 5.00826e+32
        Cl(r)    : -8.392e+31
Time = 8

smoothSolver:  Solving for Ux, Initial residual = 0.681064, Final residual = 0.0622282, No Iterations 56
smoothSolver:  Solving for Uy, Initial residual = 0.688296, Final residual = 0.0423941, No Iterations 56
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in /lib/x86_64-linux-gnu/libpthread.so.0
#3  Foam::GAMGSolver::scale(Foam::Field<double>&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, Foam::Field<double> const&, unsigned char) const at ??:?
#4  Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMatrix::smoother> const&, Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::Field<double> >&, unsigned char) const at ??:?
#5  Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#6  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) at ??:?
#7  Foam::fvMatrix<double>::solveSegregatedOrCoupled(Foam::dictionary const&) at ??:?
#8  Foam::fvMesh::solve(Foam::fvMatrix<double>&, Foam::dictionary const&) const at ??:?
#9  ? in /usr/lib/openfoam/openfoam2106/platforms/linux64GccDPInt32Opt/bin/simpleFoam
#10  __libc_start_main in /lib/x86_64-linux-gnu/libc.so.6
#11  ? in /usr/lib/openfoam/openfoam2106/platforms/linux64GccDPInt32Opt/bin/simpleFoam
Floating point exception (core dumped)

That was my issues . Do you have any idea about what's happening? Thanks in advance.

[night-hawk]

You probably have issue with boundary condition or schemes you are using.

If you are doing transient simulation consider reducing timestep value.

[sandrobrad]

HI night-hawk,
I've already checked my boundary conditions, now I am going to check my schemes. Recently I noticed that the solver runs well if I increase my desired y+ value.Honestly I don't know if it is related with my problem. Anyway, could you help me telling me how you can calculate boundary values for k and omega on an airfoil case? . Thanks in advance.
Best Regards.

[night-hawk]

Originally Posted by sandrobrad

HI night-hawk,
I've already checked my boundary conditions, now I am going to check my schemes. Recently I noticed that the solver runs well if I increase my desired y+ value.Honestly I don't know if it is related with my problem. Anyway, could you help me telling me how you can calculate boundary values for k and omega on an airfoil case? . Thanks in advance.
Best Regards.

Here you go
https://www.cfd-online.com/Tools/turbulence.php


Please correct me if I don't understand your question.

[sandrobrad]

Hello again,
I meant in my question that I need an specific number called Turbulence length scale and I don't know how to calculate it in the case of an freestream surrounding an airfoil. I found that value only in pipeflow case. Thanks for your reply btw.