[fferroni]

Hello

I am trying to find the fully developed velocity profile in a straight duct.

Rather than compute a 3D duct, and look at its profile towards the end, I would like to apply periodic boundary conditions to make it more efficient. I have never done this on openFOAM and would like some help.

I have a inlet and an outlet boundary. So:


boundary
(
inlet
{
type cyclic;
neighbourPatch outlet;
faces
(
(0 4 7 3)
);
}

outlet
{
type cyclic;
neighbourPatch inlet;
faces
(
(2 6 5 1)
);


However, now I am wondering what kind of boundary field definitions I need.
Previously I had zeroGradient or fixedValue fields (depends on variable) for both the inlet and outlet. What do I need to set for the periodic case?

Thank you very much.

Kindest Regards,

F

[stevenvanharen]

Take a look at the channelFoam tutorial. This will help you I think.

Please keep in mind that the pressure field is never periodic. Therefore you will have to split the pressure field in a periodic part and a pressure drop. This can be seen in the channelFoam solver.

[fferroni]

I see..

So, it means that I need to modify my solver?

Looking at channelFoam.c, I would need to slightly change the first part before the PISO loop and add the section correcting the driving force for a constant mass flow rate. I would not need to change any field definitions, apart from creating createGradP.H, is that correct?

In the first section, what is "sgsModel->correct(); " ?

Kindest regards,

Francesco

[stevenvanharen]

That you can do indeed, or you can use a jumpcyclic. This has different names for different OF versions I think. Browse around the OF source to see the difference.

src » finiteVolume » fields » fvPatchFields


The same holds for sgsModel->correct(); Browse around the turbulence models to see what it does.

src » turbulenceModels

[fferroni]

Hmm, I don't quite understand how jumpCyclic works (especially trying to read the source code).. Is there a tutorial on how to use it?

There is a fan tutorial in OF that apparently uses it but I'm not sure how that is relevant to what I'm trying to do...

Kind Regards,

F

[zxj160]

Originally Posted by fferroni

Hello

I am trying to find the fully developed velocity profile in a straight duct.

Rather than compute a 3D duct, and look at its profile towards the end, I would like to apply periodic boundary conditions to make it more efficient. I have never done this on openFOAM and would like some help.

I have a inlet and an outlet boundary. So:


boundary
(
inlet
{
type cyclic;
neighbourPatch outlet;
faces
(
(0 4 7 3)
);
}

outlet
{
type cyclic;
neighbourPatch inlet;
faces
(
(2 6 5 1)
);


However, now I am wondering what kind of boundary field definitions I need.
Previously I had zeroGradient or fixedValue fields (depends on variable) for both the inlet and outlet. What do I need to set for the periodic case?

Thank you very much.

Kindest Regards,

F

Dear F,

I also met the same problem that I want to set zeroGradient or fixedValue fields (depends on variable) for both the cyclic inlet and outlet. Did you find a way to achieve it?

My best regards,
Jian