Investigation on natural to ventilated cavitation considering the air-vapor interactions by Merging theory with insight on air jet location/rate effect

Cavitation is of significant practical importance since unstable flow characteristics can have noticeable consequences on objects nearby. An essential approach for controlling the cavitation flow field's instability is air injection. This work aims to conduct a numerical and experimental investigation on the natural to ventilated cavitation around a Clark Y hydrofoil. Having three phases: water, vapor, and air, the cavitation model is adjusted based on the Merging theory to consider the impact of dissolved air on cavitation. Furthermore, the Density Corrected-based Method (DCM) is used to alter the turbulence model. The experimental tests are carried out in the water tunnel, which can maintain the constant water flow rate (Q_water=490 m³⁄h) and regulate the pressure level (105–180 kPa). The Clark Y hydrofoil is fixed at an angle of attack of 8° and includes injection and pressure taps. Two holes, called Tap1-injection and Tap5-injection, are alternatively used for air injection purposes. Two cavitation numbers (σ=1.1, 1.6) and three air injection rates (Q = 0, 0.5, 1 l/min) are considered current case studies. The results demonstrate the meaningful impact of location and rate of aeration on the dynamic/average characteristics of cavitation. Increasing the air injection rate results in an increase in the pressure coefficient values, a decrease in the shedding frequency, and an elongation of the cavity with an M-shaped structure. Also, during a cycle of cavity development, air injection may take place in the reversed jet, perpendicular jet, or direct jet configurations. In addition, a close agreement between numerical and experimental results is recorded.