Numerical production of the flow field near the tip of a rotating turbine blade

Numerical analysis of the three-dimensional flow fields in an annual cascade with tip clearance and rotation and in a linear cascade is carried out. A comparison with flow visualization verifies the computational result. The comparison indicates that the numerical analysis captures the separation on the tip edge of the pressure side of the blade and the flow direction over the tip surface. However, it does not properly indicate the separation on the leading edge of the suction side. Rotation weakens the leakage flow so that the size of the separation bubble decreases on the tip surface. Large tip clearance increases leakage flow so that the tip vortex is larger and moves to the suction side.