Experimental analysis on dynamic/morphological quality of cavitation induced by different air injection rates and sites

Ventilated cavitating flow features resulting from the air injection at the hydrofoil surface are characterized based on experimental investigation. The experiments have been conducted in the cavitation tunnel at the Silesian University of Technology. The main focus of this work is to investigate how both the location of the injection hole at the surface of the hydrofoil (so-called injection site) and the injection rate have an impact on the cavitating flow in various flow conditions (i.e., different cavitation numbers). The Clark Y hydrofoil is fixed at an 8° angle of attack. In addition, three cavitation numbers, σ = 1.1, 1.25, and 1.6; five air injection rates, Q = 0, 0.25, 0.5, 0.75, and 1 l/min; and two injection sites at the surface of hydrofoil (Tap1-injection and Tap5-injection) are selected for the case studies. Furthermore, the level of dissolved air in water is kept constant at 11.7 mg/l. The unsteady measurements and high-speed imagining declare that, regardless of the injection rate, the injection site has a significant effect on the cavitation dynamic features and morphology. Moreover, it is shown that the effectiveness of air injection depends on the flow conditions.