[cyln]

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:

    SIDE11
    {
        type            cyclic;
    }

    SIDE22
    {
        type            cyclic;
    }

0/U:

    SIDE11
    {
        type            cyclic;
    }

    SIDE22
    {
        type            cyclic;
    }

constant/polyMesh/boundary :

    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