[upuli]

Dear members
I created the following blockMesh file.



convertToMeters 1.0;

vertices
(
(-0.15 -0.15 -0.005) //0
(-0.15 0.15 -0.005)
(-0.05 0.45 -0.005)
(-0.05 0.45 0.005)
(-0.15 0.15 0.005)
(-0.15 -0.15 0.005)
(0.15 -0.15 -0.005)
(0.15 0.15 -0.005)
(0.05 0.45 -0.005)
(0.05 0.45 0.005)
(0.15 0.15 0.005)
(0.15 -0.15 0.005)

);
blocks
(
hex (0 5 4 1 6 11 10 7) (30 15 30) simpleGrading (1 1 1)
hex (1 4 3 2 7 10 9 8) (30 15 30) simpleGrading (1 1 1) //edgeGrading (10 10 10 10 10 10 10 10 10 10 10 10)
);

patches
(
wall Walls
(
(6 11 10 7)
(7 10 9 8)
(0 1 4 5 )
(1 2 3 4 )

)
patch Inlet
(
(0 5 11 6)
)
patch Outlet
(
(2 8 9 3)
)
empty back
(
(0 6 7 1)
(1 7 8 2)
)
empty front
(
(5 4 10 11)
(3 9 10 4)

)
);

edges
(
);

mergePatchPairs
(
);

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


but when the checkMesh is run it gives the following error


upuli@upuli-To-be-filled-by-O-E-M:~/C/practicalcorrectdim$ checkMesh
/*---------------------------------------------------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 4.1 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
Build : 4.1
Exec : checkMesh
Date : Jul 31 2017
Time : 09:24:55
Host : "upuli-To-be-filled-by-O-E-M"
PID : 3837
Case : /home/upuli/C/practicalcorrectdim
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 polyMesh for time = 0

Time = 0

Mesh stats
points: 29791
faces: 83700
internal faces: 78300
cells: 27000
faces per cell: 6
boundary patches: 5
point zones: 0
face zones: 0
cell zones: 0

Overall number of cells of each type:
hexahedra: 27000
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 0
polyhedra: 0

Checking topology...
Boundary definition OK.
***Total number of faces on empty patches is not divisible by the number of cells in the mesh. Hence this mesh is not 1D or 2D.
Cell to face addressing 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
Walls 1800 1922 ok (non-closed singly connected)
Inlet 900 961 ok (non-closed singly connected)
Outlet 900 961 ok (non-closed singly connected)
back 900 961 ok (non-closed singly connected)
front 900 961 ok (non-closed singly connected)

Checking geometry...
Overall domain bounding box (-0.15 -0.15 -0.005) (0.15 0.45 0.005)
Mesh has 2 geometric (non-empty/wedge) directions (1 1 0)
Mesh has 2 solution (non-empty) directions (1 1 0)
All edges aligned with or perpendicular to non-empty directions.
Boundary openness (3.62619e-17 2.02015e-17 -6.50659e-15) OK.
Max cell openness = 2.17808e-16 OK.
Max aspect ratio = 5.29412 OK.
Minimum face area = 1.11111e-06. Maximum face area = 0.0002. Face area magnitudes OK.
***Zero or negative cell volume detected. Minimum negative volume: -6.66667e-08, Number of negative volume cells: 27000
<<Writing 27000 zero volume cells to set zeroVolumeCells
Mesh non-orthogonality Max: 180 average: 173.91
***Number of non-orthogonality errors: 78300.
<<Writing 78300 non-orthogonal faces to set nonOrthoFaces
***Error in face pyramids: 162000 faces are incorrectly oriented.
<<Writing 83700 faces with incorrect orientation to set wrongOrientedFaces
Max skewness = 0.805556 OK.
Coupled point location match (average 0) OK.

Failed 3 mesh checks.

End

I have attached the paraFoam file also.

Colud you please help me to solve the error

[Antimony]

Hi,

Quite possible that it your cells are twisted inside out leading to negative volume cells.

Check the log file of blockMesh. That will indicate to you the cells/faces that are twisted.

Cheers,
Antimony

[upuli]

Hi

There are list of Non orthogonal faces,Wrong oriented faces and zero volume cells ,how can I correct that.

Thanking you

rgds

Upuli

[Antimony]

Hi,

Yes, that is what I mentioned when I said twisted inside-out cells will be clear when you look at the log.

Essentially you need to change the order of your vertices in the definition of a block. It should be

hex (0 1 4 5 6 7 10 11) (30 15 30) simpleGrading (1 1 1)
hex (1 2 3 4 7 8 9 10) (30 15 30) simpleGrading (1 1 1)

instead of:

hex (0 5 4 1 6 11 10 7) (30 15 30) simpleGrading (1 1 1)
hex (1 4 3 2 7 10 9 8) (30 15 30) simpleGrading (1 1 1)

Cheers,
Antimony

[upuli]

Dear Antimony

Thank you very much for your prompt reply. I solved it according to your answer.


rgds

upuli

[upuli]

Dear members

Now the mesh is OK. The checkMesh is OK.But when I run the solver it stopped after 0.06 seconds.Following is the error message.


Time = 0.06

Courant Number mean: 0.001 max: 0.05
diagonal: Solving for flametime, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 0.114397, No Iterations 1000
smoothSolver: Solving for Uy, Initial residual = 0.999999, Final residual = 0.00789023, No Iterations 1000
DICPCG: Solving for p, Initial residual = 1, Final residual = 8.17288e-07, No Iterations 224
time step continuity errors : sum local = 0.002, global = -0.002, cumulative = -0.022
DICPCG: Solving for p, Initial residual = 0.225934, Final residual = 9.2511e-07, No Iterations 208
time step continuity errors : sum local = 0.002, global = -0.002, cumulative = -0.024
DILUPBiCG: Solving for k, Initial residual = 5.3731e-07, Final residual = 5.3731e-07, No Iterations 0
DILUPBiCG: Solving for epsilon, Initial residual = 1.19655e-06, Final residual = 4.49407e-07, No Iterations 1
#0 Foam::error:rintStack(Foam::Ostream&) at ??:?
#1 Foam::sigFpe::sigHandler(int) at ??:?
#2 ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3 double Foam::sumProd<double>(Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4 Foam::PCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#5 Foam::fvMatrix<double>::solveSegregated(Foam::dict ionary const&) at ??:?
#6 Foam::fvMatrix<double>::solve(Foam::dictionary const&) at ??:?
#7 Foam::fvMatrix<double>::solve() at ??:?
#8 ? at ??:?
#9 ? at ??:?
#10 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#11 ? at ??:?
Floating point exception (core dumped)



Reducing velocity or the time step didn't help. The solver works well with mesh of box like geometry.How can I solve the problem.

rgds Upuli

[upuli]

I have ran a customized solver in the following mesh and it worked well.convertToMeters 1.0;

vertices
(
(0.15 0.3 -0.15)
(0.15 -0.3 -0.15)
(-0.15 -0.3 -0.15)
(-0.15 0.3 -0.15)
(0.15 0.3 0.15)
(0.15 -0.3 0.15)
(-0.15 -0.3 0.15)
(-0.15 0.3 0.15)

);
blocks
(
hex (4 5 6 7 0 1 2 3) (30 60 1) simpleGrading (1 1 1) //edgeGrading (10 10 10 10 10 10 10 10 10 10 10 10)
);

patches
(
wall Walls
(
(0 4 5 1)
(2 6 7 3)
)
patch Inlet
(
(1 5 6 2)
)
patch Outlet
(
(4 0 3 7)
)
empty back
(
(0 1 2 3)
)
empty front
(
(4 7 6 5)
)
);

edges
(
);

mergePatchPairs
(
);


but when I changed the mesh to following the solver stops at 0.02S (the initial time step )

convertToMeters 1.0;

vertices
(
(-0.15 -0.15 -0.15) //0
(-0.15 0.15 -0.15)
(-0.05 0.45 -0.15)
(-0.05 0.45 0.15)
(-0.15 0.15 0.15)
(-0.15 -0.15 0.15)
(0.15 -0.15 -0.15)
(0.15 0.15 -0.15)
(0.05 0.45 -0.15)
(0.05 0.45 0.15)
(0.15 0.15 0.15)
(0.15 -0.15 0.15)

);
blocks
(
hex (0 1 4 5 6 7 10 11) (30 30 1) simpleGrading (4 4 1)
hex (1 2 3 4 7 8 9 10) (60 30 1) edgeGrading (4 4 4 4 4 4 4 4 1 1 1 1)
);

patches
(
wall Walls
(
(6 11 10 7)
(7 10 9 8)
(0 1 4 5 )
(1 2 3 4 )

)
patch Inlet
(
(0 5 11 6)
)
patch Outlet
(
(2 8 9 3)
)
empty back
(
(0 6 7 1)
(1 7 8 2)
)
empty front
(
(5 4 10 11)
(3 9 10 4)

)
);

edges
(
);

mergePatchPairs
(
);


can some one help me to get rid of the problem. changing time step did not work.

thanks

[Antimony]

Hi,

You will need to provide more information - what do you mean the run stopped? Did it crash? Do you have a log of your run? What are your BC?

Don't forget to use code blocks if you paste them directly! Really helps others to have a quick look at your case.

Cheers,
Antimony

[upuli]

The case is a combustion of solid fuels. The air is sent from the inlet and exits at the outlet. I checked the case removing the combustion of fuel and just sending air through the reactor. But the following error message appear.


Following is the error message

Time = 0.02

Courant Number mean: 0.0024 max: 0.261077
diagonal:  Solving for flametime, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for Ux, Initial residual = 0, Final residual = 0, No Iterations 0
smoothSolver:  Solving for Uy, Initial residual = 1, Final residual = 2.48371e-18, No Iterations 1
#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::divide(Foam::Field<double>&, double const&, Foam::UList<double> const&) at ??:?
#4  Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::operator/<Foam::fvPatchField, Foam::volMesh>(Foam::dimensioned<double> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:?
#5  ? at ??:?
#6  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#7  ? at ??:?
Floating point exception (core dumped)

Following are the boundary conditions for U and pressure

U

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
    Walls
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    Inlet
    {
        type            fixedValue;
        value           uniform (0 0.12 0);
    }
    Outlet
    {
        type            inletOutlet;
        //type            zeroGradient;
      inletValue      uniform (0 0 0);
     value           uniform (0 0 0);
    }
    back
    {
        type            empty;
    }
    front
    {
        type            empty;
    }
}

Pressure

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 1;

boundaryField
{
    wall
    {
        type            zeroGradient;
    }

    Outlet
    {
        type            fixedValue;
        value           uniform 1;
    }

    Inlet
    {
        type            zeroGradient;
    }

    "front.*"
    {
        type            empty;
    }

    "back.*"
    {
        type            empty;
    }
}

[upuli]

Hi
I found the reason for the error. There is field which was set to zero inside the reactor.

After setting it to the correct value the solver is running in the case.

Thank you for your prompt reply.

rgds

Upuli

[upuli]

Hi


I want some help again. In the above mesh I use to use velocity in the inlet to be set to 0.12 in the Y direction so I used the following boundary conditions. other velocities are zero. But in Paraview a different value is shown as the inlet velocity(0.00539 ms-1). How can I solve this?

FoamFile
{
version 2.0;
format ascii;
class volVectorField;
location "0";
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 1 -1 0 0 0 0];

internalField uniform (0 0 0);

boundaryField
{
Walls
{
type fixedValue;
value uniform (0 0 0);
}
Inlet
{
type fixedValue;
value uniform (0 0.12 0);
}
Outlet
{
type inletOutlet;

inletValue uniform (0 0 0);
value uniform (0 0 0);
}
back
{
type empty;
}
front
{
type empty;
}
}