Vortex suppression of the tip leakage flow over a NACA0009 hydrofoil via a passive jet induced by the double-control-hole

Abstract Tip leakage vortex (TLV) frequently occurring in bladed energy conversion machines may induce flow loss as well as cavitation. The double-curved-hole (DC hole) structures located at the 10%–25% chord near the leading edge of the foil are adopted to induce a passive jet thus suppressing the tip leakage vortex structures in this paper. The control effects and the control mechanisms of three DC hole positions are illustrated by numerical analyses based on the rotation-curvature corrected shear stress transport (SST) k-ω turbulence model and the Zwart-Gerber-Belamri (ZGB) cavitation model. The results demonstrate that the passive jet from the DC hole could divide the TLV into several parts and induce new vortical structures. The newborn vortical structures can be classified into three types: weakened tip leakage vortex (WTLV), newborn secondary tip leakage vortex (NSTLV) and hole separation vortex (HSV). The control effects for different tip clearance are greatly related to the DC hole location. Once the DC hole locates near the merger point of the tip leakage vortex and the tip separation vortex, it could achieve the best control effects. Besides, TLV core pressure could be improved thus suppressing the local cavitation, and the lift-drag ratio for different inlet velocities can be slightly reduced.