Method of T shape tip on energy improvement of a hydrofoil with tip clearance in tidal energy

Abstract Tip leakage vortex (TLV) can seriously deteriorate the flow pattern and energy performance of hydraulic machinery, which is the key component in tidal energy system. A novel method of T shape tip is proposed to improve energy performance and suppress TLV for a NACA0009 hydrofoil. The T shape tip is formed by increasing foil thickness near tip, and the effect of thickening type and control curve pattern are further evaluated by numerical simulation validated by experimental results. The T shape tip remarkably suppresses the flow separation around the pressure side tip corner and decreases the pressure gradient in the clearance, further weakening the entrainment effect of the PTLV. Three thickening types are developed. The results show that the maximum increase of energy performance is 1.76% by the half suction side T shape, and the maximum decrease of vorticity is 18.75% by the T shape, while the half pressure side T shape shows slight effect. Moreover, three curve patterns including the straight curve, arc curve and parabolic curve are evaluated. The maximum increase of energy performance is 1.41% by the arc curve T shape, and the maximum decrease of vorticity is 21.53% by the parabolic curve T shape.