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

Neepor · November 25, 2014, 13:38

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.

Neepor · November 25, 2014, 14:25

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:

rintStack(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)

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November 25, 2014, 13:38	Turbulent flow around a rotating sphere - help with k and epsilon?	#1
Neepor New Member Join Date: Nov 2014 Posts: 2 Rep Power: 0	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.

November 25, 2014, 14:25		#2
Neepor New Member Join Date: Nov 2014 Posts: 2 Rep Power: 0	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:rintStack(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)