File constant/polyMesh/boundary must be edited. First remove empty patches (w1, w3-w6), rename non-empty patches and edit their properties^12.3:

4
(
    outlet
    {
        type            patch;
        nFaces          490;
        startFace       1352948;
    }
    outlet_wall
    {
        type            mappedWall;
        sampleMode      nearestPatchFace;
        sampleRegion    solid;
        samplePatch     rotor_inner_wall;
        offsetMode      uniform;
        offset          (0 0 0);
        nFaces          33086;
        startFace       1353438;
    }
    wheel_wall
    {
        type            wall;
        nFaces          146369;
        startFace       1386524;
    }
    interface
    {
        type            mappedPatch;
        sampleMode      nearestPatchFace;
        sampleRegion    stator;
        samplePatch     ring_0;
        offsetMode      uniform;
        offset          (0 0 0);
        nFaces          12783;
        startFace       1532893;
    }
)

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