CFD Online Discussion Forums - Very high courant number, time step continuity errors and bounding epsilon

Hi all,

I am simulating flow in a double cylinder on cone cyclone and so far the iterations are wildly diverging. I am getting very high courant number, time step continuity errors and bounding epsilon. I don't know whether this is problem with my BC's. My mesh has over 600,000 cells. The flow is turbulent and I am applying the LaunderGibson turbulent model (RSM) given that the flow is strongly 3-dimensional. The checkMesh result is shown below. I have also included below the contents of the fvSchemes and fvSolution. Also attached is the BC's file for the 0 time folder. Please help thanks.

/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.x |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
Build : 1.7.x-131caa989cd3
Exec : checkMesh
Date : Mar 17 2011
Time : 10:18:11
Host : ernest-desktop
PID : 18833
Case : /home/ernest/OpenFOAM-1.7.1/novel-cyc-scaled/test2-dense
nProcs : 1
SigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
points: 116586
faces: 1253437
internal faces: 1203775
cells: 614303
boundary patches: 7
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 0
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 614303
polyhedra: 0

Checking topology...
Boundary definition OK.
Point usage OK.
Upper triangular ordering OK.
Face vertices OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
Patch Faces Points Surface topology
inlet1 284 167 ok (non-closed singly connected)
inlet2 485 291 ok (non-closed singly connected)
inlet3 259 148 ok (non-closed singly connected)
outlet1 208 124 ok (non-closed singly connected)
outlet2 312 176 ok (non-closed singly connected)
outlet3 173 105 ok (non-closed singly connected)
wall 47941 24117 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-0.61425 -0.61425 0) (0.61425 1.28388 3.04395)
Mesh (non-empty, non-wedge) directions (1 1 1)
Mesh (non-empty) directions (1 1 1)
Boundary openness (8.23856e-20 1.03745e-19 -1.27393e-19) OK.
Max cell openness = 1.70191e-16 OK.
Max aspect ratio = 8.32182 OK.
Minumum face area = 5.8284e-06. Maximum face area = 0.00236657. Face area magnitudes OK.
Min volume = 8.02989e-09. Max volume = 3.07651e-05. Total volume = 2.27731. Cell volumes OK.
Mesh non-orthogonality Max: 54.2817 average: 15.0228
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.742671 OK.

Mesh OK.

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.1 |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
default steadyState;
}

gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
grad(U) Gauss linear;
}

divSchemes
{
default none;
div(phi,U) Gauss upwind;
div(phi,k) Gauss upwind;
div(phi,epsilon) Gauss upwind;
div(phi,R) Gauss upwind;
div(R) Gauss linear;
div(phi,nuTilda) Gauss upwind;
div((nuEff*dev(grad(U).T()))) Gauss linear;
}

laplacianSchemes
{
default none;
laplacian(nuEff,U) Gauss linear limited 0.333; //Gauss linear corrected;
laplacian((1|A(U)),p) Gauss linear limited 0.333; //Gauss upwind corrected;
laplacian(DkEff,k) Gauss linear limited 0.333; //Gauss upwind corrected;
laplacian(DepsilonEff,epsilon) Gauss linear limited 0.333; //Gauss upwind corrected;
laplacian(DREff,R) Gauss linear limited 0.333; //Gauss upwind corrected;
laplacian(DnuTildaEff,nuTilda) Gauss linear limited 0.333; //Gauss upwind corrected;
}

interpolationSchemes
{
default linear;
interpolate(U) linear;
}

snGradSchemes
{
default corrected;
}

fluxRequired
{
default no;
p ;
}

// ************************************************** *********************** //

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.7.1 |
| \\ / A nd | Web: www.OpenFOAM.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
location "system";
object fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
p
{
solver PCG;
preconditioner DIC;
tolerance 1e-06;
relTol 0.01;
}

pFinal
{
solver PCG;
preconditioner DIC;
tolerance 1e-06;
relTol 0.01;
}

U
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}

k
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}

epsilon
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}

R
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}

nuTilda
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-05;
relTol 0.1;
}
}

/*SIMPLE
{
nNonOrthogonalCorrectors 5;
}*/

PISO
{
nNonOrthogonalCorrectors 5;
nCorrectors 5;
}

relaxationFactors
{
p 0.3;
U 0.5;
k 0.1;
epsilon 0.1;
R 0.3;
nuTilda 0.3;
}

// ************************************************** *********************** //