CFD Online Discussion Forums - Unexpected cyclic BC restuls

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Unexpected cyclic BC restuls

Hello, I have a computational domain which is a quarter cylinder. On the sides, I defined cyclic (periodic) BCs. I have run a transient simulation, however, on the cyclic interfaces (boundaries), there is an unexpected gradient on my flow parameters such as velocity. A screenshot of velocity contour plot is attached.

I have assigned the BCs are as follows:

0/p:

Code:

    SIDE11

    {

        type            cyclic;

    }



    SIDE22

    {

        type            cyclic;

    }

0/U:

Code:

    SIDE11

    {

        type            cyclic;

    }



    SIDE22

    {

        type            cyclic;

    }

constant/polyMesh/boundary :

Code:

    SIDE11

    {

        type            cyclic;

        inGroups        1(cyclic);

        nFaces          54131;

        startFace       16644366;

        matchTolerance  0.001;

        transform       rotational;

        neighbourPatch  SIDE22;

        rotationAxis    (1 0 0);

        rotationCentre  (0 0 0);

    }

    SIDE22

    {

        type            cyclic;

        inGroups        1(cyclic);

        nFaces          54131;

        startFace       16698497;

        matchTolerance  0.001;

        transform       rotational;

        neighbourPatch  SIDE11;

        rotationAxis    (1 0 0);

        rotationCentre  (0 0 0);

    }

Could anyone please tell me why I get such a gradient gradient very next to the cyclic interface?

Cheers

It looks if there is a wall function in action.

Hello Uwe,

Thanks for your reply. This is a laminar simulation, so there are only U and p within the 0 directory. The boundary conditions for the cyclic boundaries are as above. I do no use any wall function in the simulation.

I just cannot find the reason behind this problem :/

Thanks

Does anyone have another suggestion?