Turbulent flow around a rotating sphere - help with k and epsilon?
 

Hello,

I am new to CFD. I am trying to model flow around a rotating sphere (baseball). I was able to solve it with icoFoam but I am having trouble using a turbulent solver, specifically with k and epsilon.

Right now I am using pisoFoam (RAS k-epsilon) solver.

I tried to calculate k and epsilon. Reading this gave me the impression that external flow over an object which starts moving from standstill (like a baseball) is a low turbulence case and so my turbulent intensity should be less than one percent.

So I set Intensity = 0.005, mean flow velocity = 34 m/s (speed of the throw) and Length = 0.038 m (the radius of the baseball).

I used the formulas here with Cu^1, not the ones with Cu^(3/4)

You can download my case folder here.

Any help in getting my solution to converge would be great! Thanks.

Here is my output by the way.

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 turbulence model type RASModel
Selecting RAS turbulence model kEpsilon
--> Upgrading k to employ run-time selectable wall functions
Backup original k to k.old
Writing updated k
--> Upgrading epsilon to employ run-time selectable wall functions
Backup original epsilon to epsilon.old
Writing updated epsilon
--> Creating nut to employ run-time selectable wall functions
Writing new nut

Starting time loop

Time = 0.005

Courant Number mean: 0.00141771 max: 1.14865
GAMG: Solving for p, Initial residual = 1, Final residual = 0.0462013, No Iterations 1
time step continuity errors : sum local = 0.000131, global = -6.54747e-06, cumulative = -6.54747e-06
GAMG: Solving for p, Initial residual = 0.0959969, Final residual = 0.00578467, No Iterations 1
time step continuity errors : sum local = 3.689e-05, global = 6.57472e-07, cumulative = -5.89e-06
GAMG: Solving for p, Initial residual = 0.0204946, Final residual = 5.26281e-07, No Iterations 14
time step continuity errors : sum local = 3.5884e-09, global = 2.04918e-09, cumulative = -5.88795e-06
smoothSolver: Solving for epsilon, Initial residual = 0.0278695, Final residual = 2.19596e-06, No Iterations 2
bounding epsilon, min: -8.87 max: 1315.52 average: 0.0912143
smoothSolver: Solving for k, Initial residual = 1, Final residual = 1.93526e-06, No Iterations 3
bounding k, min: -1.59893 max: 187.775 average: 0.328556
ExecutionTime = 24.21 s ClockTime = 24 s

Time = 0.01

Courant Number mean: 0.0021519 max: 0.744259
GAMG: Solving for p, Initial residual = 0.0185297, Final residual = 0.00144005, No Iterations 1
time step continuity errors : sum local = 9.94728e-06, global = -3.64742e-06, cumulative = -9.53537e-06
GAMG: Solving for p, Initial residual = 0.00947602, Final residual = 0.00088196, No Iterations 1
time step continuity errors : sum local = 6.12405e-06, global = -1.79647e-06, cumulative = -1.13318e-05
GAMG: Solving for p, Initial residual = 0.00763211, Final residual = 4.49211e-07, No Iterations 10
time step continuity errors : sum local = 3.12693e-09, global = -1.7152e-10, cumulative = -1.1332e-05
smoothSolver: Solving for epsilon, Initial residual = 0.996161, Final residual = 1.27981e-06, No Iterations 5
bounding epsilon, min: -9.92401 max: 5.61147e+07 average: 64.7603
smoothSolver: Solving for k, Initial residual = 0.93545, Final residual = 1.19486e-06, No Iterations 4
ExecutionTime = 41.4 s ClockTime = 41 s

Time = 0.015

Courant Number mean: 0.00225062 max: 0.734234
GAMG: Solving for p, Initial residual = 0.0125908, Final residual = 0.0011071, No Iterations 1
time step continuity errors : sum local = 7.71505e-06, global = -7.43822e-09, cumulative = -1.13394e-05
GAMG: Solving for p, Initial residual = 0.00997975, Final residual = 0.000211546, No Iterations 2
time step continuity errors : sum local = 1.48301e-06, global = -2.25384e-08, cumulative = -1.1362e-05
GAMG: Solving for p, Initial residual = 0.0115299, Final residual = 6.31028e-07, No Iterations 11
time step continuity errors : sum local = 4.43927e-09, global = -2.7564e-10, cumulative = -1.13623e-05
smoothSolver: Solving for epsilon, Initial residual = 0.999579, Final residual = 1.4531e-07, No Iterations 2
bounding epsilon, min: -342344 max: 6.52944e+09 average: 9517.55
smoothSolver: Solving for k, Initial residual = 0.308644, Final residual = 9.45582e-06, No Iterations 58
bounding k, min: -3781.99 max: 32880.5 average: 0.891005
ExecutionTime = 65.28 s ClockTime = 65 s

Time = 0.02

Courant Number mean: 0.00228562 max: 2.69578
GAMG: Solving for p, Initial residual = 0.013775, Final residual = 0.000528505, No Iterations 2
time step continuity errors : sum local = 3.71415e-06, global = -2.52121e-07, cumulative = -1.16144e-05
GAMG: Solving for p, Initial residual = 0.0213888, Final residual = 0.000628028, No Iterations 2
time step continuity errors : sum local = 4.48486e-06, global = -1.11594e-06, cumulative = -1.27303e-05
GAMG: Solving for p, Initial residual = 0.0352789, Final residual = 8.76741e-07, No Iterations 13
time step continuity errors : sum local = 6.3759e-09, global = -4.39911e-10, cumulative = -1.27308e-05
smoothSolver: Solving for epsilon, Initial residual = 1, Final residual = 3.0603e-11, No Iterations 1
bounding epsilon, min: -70535.4 max: 2.05589e+09 average: 7600.19
#0 Foam::error::printStack(Foam::Ostream&) at ??:?
#1 Foam::sigFpe::sigHandler(int) at ??:?
#2 in "/lib/x86_64-linux-gnu/libc.so.6"
#3 Foam::lduMatrix::residual(Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, unsigned char) const at ??:?
#4 Foam::lduMatrix::residual(Foam::Field<double> const&, Foam::Field<double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, unsigned char) const at ??:?
#5 Foam::smoothSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#6 Foam::fvMatrix<double>::solveSegregated(Foam::dict ionary const&) at ??:?
#7 Foam::fvMatrix<double>::solve(Foam::dictionary const&) at ??:?
#8 Foam::SolverPerformance<double> Foam::solve<double>(Foam::tmp<Foam::fvMatrix<doubl e> > const&) at ??:?
#9 Foam::incompressible::RASModels::kEpsilon::correct () at ??:?
#10
at ??:?
#11 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#12
at ??:?
Floating point exception (core dumped)