OpenChannel with Two Cylinders in icoFoam
 

Hi,

I am trying to set up a case, like cavity, in icoFoam folder.

The case is to simulate 3D water flow around two tandem cylinders in open channel.

The mesh is generated with Gridgen (see attached figure, top view), hexahedral.

The left is inlet boundary and right is outlet boundary. The surface give symmetry boundary and the side and bottom wall are wall boundary.

velocity-inlet-4
{
type patch;
nFaces 56;
startFace 16992;
}
wall-5
{
type wall;
nFaces 4120;
startFace 17048;
}
symmetry-6
{
type symmetryPlane;
inGroups 1(symmetryPlane);
nFaces 3528;
startFace 21168;
}
outflow-8
{
type patch;
nFaces 56;
startFace 24696;
}


Initial boundary: P
dimensions [0 2 -2 0 0 0 0];

internalField uniform 0;

boundaryField
{
velocity-inlet-4
{
type zeroGradient;
}

wall-5
{
type zeroGradient;
}
outflow-8
{
type fixedValue;
value uniform 0;
}
symmetry-6
{
type symmetryPlane;
}
}

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

internalField uniform (0 0 0);

boundaryField
{
velocity-inlet-4
{
type fixedValue;
value uniform (0.1 0 0);
}
outflow-8
{
type zeroGradient;
}
symmetry-6
{
type symmetryPlane;
}
wall-5
{
type fixedValue;
value uniform (0 0 0);
}

}

I also changed the deltaT to make sure the Courant number is less than 1.
For the fvschemes and fvsolution i didn't change them.

With these modifies, i run the checkMesh. The mesh is ok.
And the icoFoma,
The Courant number increases too high and make the calculation break down.

Could anyone help me out?

Best

Hello

maybe assign an appropriate initial condition help for numerical convergence,
i suggest to use for example:
for U:
also post your error log file, it may help OpenFOAM users to help you

Hi Nima,

I tried to change the initial condition you suggested, but it still has the same problem.

Now I post the error message

Courant Number mean: 4.27005e+101 max: 1.43938e+104
#0 Foam::error::printStack(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::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#5
at ??:?
#6
at ??:?
#7
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)

use a very small time step for example 1e-6 or 1e-08

no it does not work i am having the same problem

post your case here

Time = 0.000145

Courant Number mean: 1.41367e+82 max: 1.17207e+86
DILUPBiCG: Solving for Ux, Initial residual = 0.999949, Final residual = 5.82071, No Iterations 1001
DILUPBiCG: Solving for Uy, Initial residual = 0.999934, Final residual = 6.42952, No Iterations 1001
DILUPBiCG: Solving for Uz, Initial residual = 0.999958, Final residual = 4.32912, No Iterations 1001
DICPCG: Solving for p, Initial residual = 1, Final residual = 23.5112, No Iterations 1001
time step continuity errors : sum local = 1.55446e+90, global = 1.20778e+75, cumulative = 1.20778e+75
DICPCG: Solving for p, Initial residual = 0.946822, Final residual = 8.63811, No Iterations 1001
time step continuity errors : sum local = 2.01094e+92, global = -3.33867e+76, cumulative = -3.2179e+76
ExecutionTime = 1546.13 s ClockTime = 1553 s

Time = 0.00015

Courant Number mean: 3.61103e+92 max: 4.64632e+96
#0 Foam::error::printStack(Foam::Ostream&) in "/opt/openfoam220/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/opt/openfoam220/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2 in "/lib/x86_64-linux-gnu/libc.so.6"
#3 double Foam::sumProd<double>(Foam::UList<double> const&, Foam::UList<double> const&) in "/opt/openfoam220/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#4 Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/openfoam220/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#5
in "/opt/openfoam220/platforms/linux64GccDPOpt/bin/icoFoam"
#6
in "/opt/openfoam220/platforms/linux64GccDPOpt/bin/icoFoam"
#7
in "/opt/openfoam220/platforms/linux64GccDPOpt/bin/icoFoam"
#8
in "/opt/openfoam220/platforms/linux64GccDPOpt/bin/icoFoam"
#9 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#10
in "/opt/openfoam220/platforms/linux64GccDPOpt/bin/icoFoam"
Floating point exception (core dumped)

my delta t was 0.000005 u was 0.0001

Dear

your solution does not converge in each iteration, look that after 1001 iteration your residual is uprising, i said post your whole case :) not just a few last error log :)

which files do u want

post the contents of 0, constant and system ;) the whole case :P, then i can try it by my own :D

case icoFoam
directory 0
file p
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 2.2.0 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
object p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform 0;

boundaryField
{
movingWall
{
type zeroGradient;
}

fixedWalls
{
type zeroGradient;
}

frontAndBack
{
type zeroGradient;
}
}

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

directory 0
file u
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField uniform (0 0 0);

boundaryField
{
movingWall
{
type fixedValue;
value uniform (0 0 1);
}

fixedWalls
{
type fixedValue;
value uniform (0 0 1);
}

frontAndBack
{
type fixedValue;
value uniform (0 0 0);
}
}

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

transportProperties

nu nu [ 0 2 -1 0 0 0 0 ] 0.01;

boundary
3
(
movingWall
{
type patch;
nFaces 10;
startFace 252345;
}
fixedWalls
{
type patch;
nFaces 10;
startFace 252355;
}
frontAndBack
{
type patch;
nFaces 25198;
startFace 252365;
}
)

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

case
 

i have created a cylicrical mesh with inlet and outlet of radius 100 and diam,eter of 1000

Hi Nimasam,

I have attached constant folders.
Since the size of constant folds exceed the limitation, i split it into four.
Due to the upload file type, i add .tar.gz suffix to each split file, so first please delete the suffix .tar.gz and then
Using
cat constant* > constant.tar.gz
to recover the constant files.

Here is the 0 and system folders.

you could create a zip file, and you could upload it!, if its size was more than site allowed upload size, you could use dropbox or 4shared to upload your case :)

also it would be helpful for you to read this post, it shows you how to post in forum :) to receive much more help

Hi Nimasam,

Thanks for the suggestion.
Could you help me check this case?
I attached the link,
https://www.dropbox.com/s/5m2vw11e6a...ylinder.tar.gz

i am posting my case

well, check your mesh, again, you assign a wrong patch as out-flow

your mesh has wrong assigned patch, also severely non-orthogonal face, build new mesh

How didi you find the wrong boundary.
I was using checkMesh, and it looks everything is ok.

your mesh configure is fine, as i said before, you assigned wrong patch as out-flow, you can see each patch by paraview, just click on patch name , and remove other patch name on paraview ;)

Hi Nimasam,

Thank you.
I changed the out-flow patch.
And now it can calculate, but some problems still exist, see figures below

There is no flow in the area (blue region) around the cylinders (represented by the gray circle). I have double checked the wall boundary, and it's right. So what's wrong with the blue region?

In the second figure, large velocity is found at the surface. Note different scale for these two figures. I gave a symmetryPlane boundary for the surface. Why did it cause big value at the surface?

If you want, find the case at
https://www.dropbox.com/s/vb3ge8jm4t...linders.tar.gz

i feel you need to increase cells number in z direction to atleast 4 cells, maybe it solves your problem

Hi Nima

I increased the cells number in z direction to 8, but it didn't work.
Do you have any other ideas on this?
Thank you.