File constant/polyMesh/boundary must be edited. First remove empty patches (w1-w3, w5,w6), rename non-empty patches and edit their properties^13.3:

4
(
    inlet
    {
        type            patch;
        nFaces          425;
        startFace       1807730;
    }
    inlet_wall
    {
        type            mappedWall;
        sampleMode      nearestPatchFace;
        sampleRegion    solid;
        samplePatch     rotor_inner_wall;
        offsetMode      uniform;
        offset          (0 0 0);
        nFaces          20150;
        startFace       1808155;
    }
    rotor_wheel_wall
    {
        type            wall;
        nFaces          108040;
        startFace       1828305;
    }
    interface
    {
        type            mappedPatch;
        sampleMode      nearestPatchFace;
        sampleRegion    stator;
        samplePatch     ring_0;
        offsetMode      uniform;
        offset          (0 0 0);
        nFaces          23868;
        startFace       1936345;
    }
)

Patch inlet is a standard type patch, fluid can flow through. Patch inlet_wall is a wall of type mappedWall because heat transfer from fluid to solid is assumed. Patch rotor_wheel_wall is a standard wall. Patch interface is mappedPatch to be connected to stator region of the model.