Acoustic Detection of Cavitation Inception

Cavitation phenomenon can cause deterioration of the hydraulic performance, damage by pitting, material erosion, structure vibration and noise in fluid machinery, turbomachinery, ship propellers and in many other applications. Therefore, it is important to detect inception of cavitation phenomenon. An experimental study has been carried out in order to investigate the noise radiated by various cavitating sources to determine the validity of noise measurements for detecting the onset of cavitation. Measurements have been made measuring the noise radia¬ted by a number of configurations in a water tunnel at various operating condition to determine the onset of cavita¬tion. The measurements have been conducted over a frequency range of 31.5 Hz to 31.5 kHz in onethird octave bands. The on¬set of cavitation was measured visually through a Perspex side of the working section of the water tunnel. Moreover, a theoretical estimate of the pressure radiated from the cavitation nuclei at their critical radii and their frequency was presented. Tests indicated that, generally, at the point of visual incep¬tion there was a marked rise of the sound pressure level in the highfrequency noise, whilst the lowfrequency noise in¬creased as the cavitation developed. This finding was supported by the theoretical estimate of the pulsating frequency of cavitation nuclei. The results illustrated that the visual observations of inception confirm the noise measurements.