Flow and cavity measurements in a super-cavitating propeller

The design of super-cavitating propellers takes advantage of the development of air cavities on the blades’ surface to reduce drag and, ultimately, increase efficiency. The mechanism of flow modification induced by the development of a cavity on the propeller blades was investigated experimentally via phase-locked laser Doppler velocimetry measurements. A large cavity extending beyond the blades’ trailing edge and enclosing the back of the blades was identified at high loading conditions. A robust methodology to quantitatively analyze the size of the cavity is presented. The analysis of the flow fields showed that, under fully developed cavitation conditions, the acceleration of the axial and tangential flow in the inter-blade region was observed, accompanied by a reduction in tip-vortex development.