An Experimental and Numerical Study of Tip Vortex Cavitation

The article presents the results of the research project concerning tip vortex cavitation. This form of cavitation is very important in operation of many types of rotary hydraulic machines, including pumps, turbines and marine propellers. Tip vortex cavitation generates noise, vibration and erosion. It should be eliminated or significantly limited during the design of these types of machines. The objective of the project was to develop an accurate and reliable method for numerical prediction of tip vortex cavitation, which could serve this purpose. The project consisted of the laboratory experiments and numerical calculations. In the laboratory experiments tip vortex cavitation was generated behind a hydrofoil in the cavitation tunnel and the velocity field around the cavitating kernel was measured using the Particle Image Velocimetry method. Measurements were conducted in three cross-sections of the cavitating tip vortex for a number of angles of attack of the hydrofoil and for several values of the cavitation index. In the course of numerical calculations two commercial CFD codes were used: Fluent and CFX. Several available approaches to numerical modeling of tip vortex cavitation were applied and tested, attempting to reproduce the experimental conditions. The results of calculations were compared with the collected experimental data. The most promising computational approach was identified.