Flow and hydrodynamic noise characteristics of coupled supercavitation and submerged gas jet field

This study experimentally investigates the hydrodynamic noise characteristics of the coupled jet–ventilated supercavitation flow field in a water tunnel. Based on distinct deflation modes induced by the coupling interaction between the gas jet and ventilated supercavity, four flow regimes are classified: intact cavity (IC), partially broken cavity (PBC), pulsating fluctuating cavity (PFC), and wake-mixing (WM). The overall sound pressure level (OASPL) and proper orthogonal decomposition modes of the coupled flow are compared with those of the ventilated supercavity and jet flows. The results indicate that at low-order fluctuation modes, IC, and ventilated cavitation are nearly identical; PBC low-order flow patterns more closely resemble ventilated supercavitation, whereas PFC and WM are closer to jet flow. Transient experimental results reveal that hydrophone signals are strongly correlated with cavity evolution. When the gas jet penetrates the cavity interface, a bulging-necking structure emerges during the gas deflation process, substantially elevating the OASPL of the coupled flow field. Meanwhile, the ventilated supercavity produces a remarkable noise reduction effect on the tail jet for specific working conditions. Under the condition of Fr = 7.5 and jet flow rate Q_J = 50 SLPM, the jet ejects along the trailing cavity induced by the ventilated supercavity and becomes entrained and merged with the cavity leakage wake, achieving a maximum noise reduction of 13 dB relative to the pure jet condition and 8 dB relative to ventilated supercavity. Finally, analyses reveal the effects of key parameters on the noise characteristics of the coupled flow. The wake interface fluctuations and micro-bubble clusters are strongly correlated with the radiated noise in the wake region.