Investigation of vortical cavitating flows in tip leakage region of a hydrofoil

Experimental investigations of unsteady cavitating flows in a hydrofoil tip leakage region are conducted to highlight the development of cavitation with various cavitation numbers. The experiments were taken in a closed cavitation tunnel, during which high speed camera was used to capture the cavitation patterns. Image processing was also used to get further analysis. Besides, cavitating vortex model is proposed to describe the development of vortex cavitation. Based on the results, three stages can be defined as the decrease of cavitation number. In the first stage, called the inception of tip leakage vortex cavitation, a rapid onset-growth-collapse process of the vortex cavitation can be observed near the middle and rear parts of the hydrofoil. In the second stage, called the development of attached leakage cavitation, aforementioned vortex cavitation develops gradually with non-axisymmetric and twists rotation, and attached sheet cavitation inside the gap with strong unsteadiness can be observed neat the middle part of the hydrofoil. In the last stage, called formation and development of jet shear layer cavitation, vortex cavitation stretches towards downstream, and aforementioned attached cavitation develops beyond the gap and combines with the vortex cavitation, to form the triangle cavitating region. © 2015, China Ship Scientific Research Center. All right reserved.