have you tried to place a rotating mesh around the turbine?
Hello Ijihiji Ijijijij,
1) You definitely need to encompass ALL the blade surfaces in a local rotating region placing the cylindrical rotating region interface (RRI) in the middle of the minimum gap between the blades and the nearest stator wall.
2) You definitely need much finer mesh to resolve the flow around the blade and at both sides of RRI. Minimum 3-fluid cells are required on both sides of the RRI.
Hope this help