[Qihao]

I was trying to solve channel flow with fully developed flow at inlet as well as outlet using pisoFoam. I would like to know how to implement periodic/cyclic boundary condition (translational) in inlet as well as outlet. I can add a source item (fvoption) of meanvelocityForce to driven the river flow. while for the turbulence model, how can I give a similar boundary for the turbulence kinetic energy like this? I think the single cyclic boundary for the turbulence kinetic energy maybe not correct.

[RobertHB]

Dear Qihao,
the cyclic boundary conditions in Openfoam work pairwise. So you have to define which connect together. Take a look at this code. Here inlet and outlet are connected via cyclic patches, so the fluid that "leaves" at the outlet will reenter at the inlet. In your 0/U/p/k/e/w ... dicts you will have to specify the patches using "type cyclic".

    inlet
    {
        type cyclic;
        neighbourPatch outlet;
        faces
        (
            (0 4 7 3)
        );
    }
    outlet
    {
        type cyclic;
        neighbourPatch inlet;
        faces
        (
            (2 6 5 1)
        );
    }

[Qihao]

Dear Robert,

I have defined the cyclic boundary for both of the turbulence variables, like velocity and pressure. turbulence kinetic energy. but I need the driving force to drive flow, so I add source item in the inlet for the velocity, but the turbulence kinetic energy also have transport equation, how can I give the force like meanvelocityforce for the turbulence kinetic energy?

[RobertHB]

Have you tried setting the internalField value in 0/k and 0/e? After that the turbulence parameters should be determined from within your simulation.

[Qihao]

Originally Posted by RobertHB

Have you tried setting the internalField value in 0/k and 0/e? After that the turbulence parameters should be determined from within your simulation.

yes, I calculate it and define them in the internalField, and I can see the result of turbulence kinetic energy transport. so the cyclic boundary for the turbulence kinetic energy is enough ? can I understand like this? the meanvelocityforce in the field can also drive turbulence energy transport?

[RobertHB]

Thats my understanding, yes.

[hulli]

Hi,

as far I understood you want to simualte a turbulent channel case with cyclic boundary conditions. Rigth? In order to get the turbulences you might either wait a long time until they develop (at least for a flat plate case you get an idea if you calculate the entrance length), or you speed this up by using the perturbU or boxturb applications, to generate some withe noise that speed the generaion of a turbulent case extreamly up, and is more or less what was done in the channel 3xx tutorial case... I hope that helps best H