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Ahmed body simulation

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Old   July 21, 2016, 06:09
Default Ahmed body simulation
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Michal
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Hi,

I have a question about ahmed body simulation. Actually II'm preparing my model, and i tried to calculate values of turbulence dissipation and kinetic energy.
I used an equations:
Reynolds number
Re=U*L/nu=40*1,044/1,5e-5=2784000
Turbulence Intensity:
I=0,16*Re^(-1/8)=0,16*2784000^(-1/8)=0,025
Kinetic Energy:
k=1,5*(UI)^2=1,5*(0,025*40)^2=1,5

And something is wrong, because k should be equal to 0,287, due to https://www.simscale.com/docs/conten...dBody.html#id7

I'm almost sure, that my equation for I is wrong. Do you know other equations which can give me proper value of k?

Best regards
Michal
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Old   July 22, 2016, 05:26
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Michal
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And the second question is about error:
Quote:
Create time

Create mesh for time = 0


SIMPLE: no convergence criteria found. Calculations will run for 780 steps.

Reading field p

Reading field U

Reading/calculating face flux field phi

Selecting incompressible transport model Newtonian
Selecting turbulence model type RAS
Selecting RAS turbulence model kOmegaSST
Selecting patchDistMethod meshWave
kOmegaSSTCoeffs
{
alphaK1 0.85;
alphaK2 1;
alphaOmega1 0.5;
alphaOmega2 0.856;
gamma1 0.555556;
gamma2 0.44;
beta1 0.075;
beta2 0.0828;
betaStar 0.09;
a1 0.31;
b1 1;
c1 10;
F3 false;
}

No MRF models present

No finite volume options present


Starting time loop



Time = 1

smoothSolver: Solving for Ux, Initial residual = 0.999996, Final residual = 0.084107, No Iterations 2
smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 0.0895307, No Iterations 4
smoothSolver: Solving for Uz, Initial residual = 0.999994, Final residual = 0.0651902, No Iterations 2
#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:ICPreconditioner::calcReciprocalD(Foam::Fie ld<double>&, Foam::lduMatrix const&) at ??:?
#4 Foam:ICPreconditioner:ICPreconditioner(Foam::l duMatrix::solver const&, Foam::dictionary const&) at ??:?
#5 Foam::lduMatrix:reconditioner::addsymMatrixConst ructorToTable<Foam:ICPreconditioner>::New(Foam:: lduMatrix::solver const&, Foam::dictionary const&) at ??:?
#6 Foam::lduMatrix:reconditioner::New(Foam::lduMatr ix::solver const&, Foam::dictionary const&) at ??:?
#7 Foam::PCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#8 Foam::GAMGSolver::solveCoarsestLevel(Foam::Field<d ouble>&, Foam::Field<double> const&) const at ??:?
#9 Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMa trix::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 ??:?
#10 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#11 Foam::fvMatrix<double>::solveSegregated(Foam::dict ionary const&) at ??:?
#12 Foam::fvMatrix<double>::solve(Foam::dictionary const&) at ??:?
#13 Foam::fvMatrix<double>::solve() at ??:?
#14 ? at ??:?
#15 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#16 ? at ??:?
Do someone have an idea what happened. I see that it is something with GAMGSolver.
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Old   December 18, 2020, 07:01
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Manuel Fermin Fonseca
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Greetings i'm with the same doubt, plus the length characteristic may be the height because the eddy must not be larger that one side.

Quote:
Originally Posted by miku11 View Post
Hi,

I have a question about ahmed body simulation. Actually II'm preparing my model, and i tried to calculate values of turbulence dissipation and kinetic energy.
I used an equations:
Reynolds number
Re=U*L/nu=40*1,044/1,5e-5=2784000
Turbulence Intensity:
I=0,16*Re^(-1/8)=0,16*2784000^(-1/8)=0,025
Kinetic Energy:
k=1,5*(UI)^2=1,5*(0,025*40)^2=1,5

And something is wrong, because k should be equal to 0,287, due to https://www.simscale.com/docs/conten...dBody.html#id7

I'm almost sure, that my equation for I is wrong. Do you know other equations which can give me proper value of k?

Best regards
Michal
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