New insights into cloud cavitation noise spectrum

Cloud cavitation induces intense underwater radiation noise, with complex spectral characteristics that remain insufficiently understood. This study explores the underlying mechanisms through experiments and simulations on a twisted hydrofoil. Beyond the well-known harmonic tones linked to cavity shedding frequency, two key spectral characteristics were identified: a series of lock-in frequency features and a consistent high-frequency decay rate. Experimental and numerical results reveal that tunnel acoustic modes and hydrofoil structural modes contribute to the lock-in features at their respective natural frequencies, while the collapse of cascaded microscale bubbles drives the regular high-frequency noise decay at a rate of −4 dB/octave. These findings contribute to a deeper understanding of cloud cavitation noise, and provide valuable insights for modifying existing cavitation noise prediction models.