Correlation of vortex-induced cavitation bubble dynamics and acoustic emissions

Abstract

The bubble dynamics and corresponding acoustic emission from low‐event rate cavitation inception due to the interactions of a pair of parallel counter‐rotating vortex was studied experimentally in a water tunnel. The measured bandwidth of the acoustic pulse from the growth/collapse of a small isolated cavitation bubble is more than 200 kHz, and the measured pulse duration is ∼15–20 μs. The underlying vortical flow, static pressure, and nuclei distribution were characterized and are reported. These fluid and flow parameters influenced the acoustic signal, and dynamics of the cavitation bubbles. Details of the acoustic signature of the cavitation bubble were investigated during its inception, growth, splitting, and collapse. In the chosen flow field, it was found that during bubble growth, the acoustic signal is the strongest with the bulk of the signal energy in frequencies between 1 kHz and 6 kHz. Here, the frequency content of the acoustic signal during inception and growth was related to the volumetric change of the bubble measured from images taken with a high‐speed video camera with a correlation of 84%. [Work supported by ONR.]