[tfigueiro]

Hello,

I am an undergraduate ME student (3rd year) learning the basics of OpenFoam, and of CFD in general, in order to simulate air flow and air properties throughout a small ventilated room.

To begin with, I have built an extremely simplified mesh (attachments) with one inlet (mechanical insuflation) and one outlet (to atmosphere, no external work), which will then be replaced by a more realistic model that will be imported from Solidworks.

Screenshot from 2015-04-01 15:18:11.jpg


As a first approach, I am trying to run a simpleFoam case to find the velocity and pressure fields. (later on I am going to choose appropriate solvers to account for temperature fields, CO2 distribution and humidity)

While running, and after a few iterations, the terminal displayed many error messages which I lack the knowledge to understand. I was hoping someone here could be so kind as to shed some light on this for me, and try to point me in the right direction.

tiago@tiago-SATELLITE-L50-B:~/OpenFOAM/tiago-2.3.1/run/proj2015/mesh1-simple$ simpleFoam
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.3.1-bcfaaa7b8660
Exec   : simpleFoam
Date   : Apr 01 2015
Time   : 14:49:38
Host   : "tiago-SATELLITE-L50-B"
PID    : 15348
Case   : /home/tiago/OpenFOAM/tiago-2.3.1/run/proj2015/mesh1-simple
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
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 RAS turbulence model kEpsilon
kEpsilonCoeffs
{
    Cmu             0.09;
    C1              1.44;
    C2              1.92;
    sigmaEps        1.3;
}

No finite volume options present


SIMPLE: convergence criteria
    field p	 tolerance 0.01
    field U	 tolerance 0.001
    field "(k|epsilon|omega)"	 tolerance 0.001


Starting time loop

streamLine streamLines:
    automatic track length specified through number of sub cycles : 5

Time = 1

smoothSolver:  Solving for Uy, Initial residual = 1, Final residual = 0.0338637, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 1, Final residual = 0.0455047, No Iterations 1
GAMG:  Solving for p, Initial residual = 1, Final residual = 2.48592e+38, No Iterations 1000
time step continuity errors : sum local = 3.52749e+36, global = -9.0072e+17, cumulative = -9.0072e+17
smoothSolver:  Solving for epsilon, Initial residual = 1, Final residual = 8.75374e+17, No Iterations 1000
smoothSolver:  Solving for k, Initial residual = 1, Final residual = 6.77587e-19, No Iterations 1
ExecutionTime = 91.22 s  ClockTime = 92 s

Time = 2

smoothSolver:  Solving for Uy, Initial residual = 0.891086, Final residual = 0.0544469, No Iterations 18
smoothSolver:  Solving for Uz, Initial residual = 0.969701, Final residual = 0.0893473, No Iterations 16
GAMG:  Solving for p, Initial residual = 0.370998, Final residual = 0.0313951, No Iterations 5
time step continuity errors : sum local = 4.75755e+40, global = 4.18573e+25, cumulative = 4.18573e+25
smoothSolver:  Solving for epsilon, Initial residual = 0.5389, Final residual = 2.31757e-18, No Iterations 1
smoothSolver:  Solving for k, Initial residual = 3.50512e-17, Final residual = 3.50512e-17, No Iterations 0
ExecutionTime = 93.43 s  ClockTime = 94 s

Time = 3

smoothSolver:  Solving for Uy, Initial residual = 0.394479, Final residual = 3.00805e+15, No Iterations 1000
smoothSolver:  Solving for Uz, Initial residual = 0.482591, Final residual = 7.70933e+15, No Iterations 1000
GAMG:  Solving for p, Initial residual = 0.648096, Final residual = 0.119751, No Iterations 1000
time step continuity errors : sum local = 2.78123e+96, global = -1.23512e+80, cumulative = -1.23512e+80
smoothSolver:  Solving for epsilon, Initial residual = 1, Final residual = 2.37786e-05, No Iterations 2
smoothSolver:  Solving for k, Initial residual = 1.32469e-29, Final residual = 1.32469e-29, No Iterations 0
ExecutionTime = 197.8 s  ClockTime = 198 s

Time = 4

smoothSolver:  Solving for Uy, Initial residual = 0.999996, Final residual = 2.07884e-17, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.620253, Final residual = 0.0434177, No Iterations 1
GAMG:  Solving for p, Initial residual = 1.54528e-19, Final residual = 1.54528e-19, No Iterations 0
time step continuity errors : sum local = 8.90784e+95, global = -9.359e+78, cumulative = -1.32871e+80
smoothSolver:  Solving for epsilon, Initial residual = 0.538475, Final residual = 1.24415e-17, No Iterations 1
smoothSolver:  Solving for k, Initial residual = 1.07124e-29, Final residual = 1.07124e-29, No Iterations 0
ExecutionTime = 199.05 s  ClockTime = 200 s

Time = 5

smoothSolver:  Solving for Uy, Initial residual = 0.465389, Final residual = 0.0389067, No Iterations 20
smoothSolver:  Solving for Uz, Initial residual = 0.467491, Final residual = 0.0366824, No Iterations 20
#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::DICPreconditioner::calcReciprocalD(Foam::Field<double>&, Foam::lduMatrix const&) at ??:?
#4  Foam::DICPreconditioner::DICPreconditioner(Foam::lduMatrix::solver const&, Foam::dictionary const&) at ??:?
#5  Foam::lduMatrix::preconditioner::addsymMatrixConstructorToTable<Foam::DICPreconditioner>::New(Foam::lduMatrix::solver const&, Foam::dictionary const&) at ??:?
#6  Foam::lduMatrix::preconditioner::New(Foam::lduMatrix::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<double>&, Foam::Field<double> const&) const at ??:?
#9  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 ??:?
#10  Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#11  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) at ??:?
#12  Foam::fvMatrix<double>::solve(Foam::dictionary const&) at ??:?
#13  
 at ??:?
#14  
 at ??:?
#15  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#16  
 at ??:?
[1]+  Exit 1                  paraFoam  (wd: ~/OpenFOAM/tiago-2.3.1/run/proj2015/mesh1-piso)
(wd now: ~/OpenFOAM/tiago-2.3.1/run/proj2015/mesh1-simple)
Floating point exception (core dumped)

[tfigueiro]

Here is a link for the case I've set up:

https://www.dropbox.com/s/lnxp2ugc03...le.tar.gz?dl=0

[thiagopl]

Hi Tiago,

Take a look here at your final residuals for pressure in your first step:

GAMG:  Solving for p, Initial residual = 1, Final residual = 2.48592e+38, No Iterations 1000
time step continuity errors : sum local = 3.52749e+36, global = -9.0072e+17, cumulative = -9.0072e+17

You certainly have a problem here. I think you could check your pressure BC's and the /0 folder for pressure, then check your inlet and outlet BC's.

Regards.

[tfigueiro]

Thank you so much for your help. I have since realized that in fact my BC's were poorly set and have achieved convergence after correcting them.