Abstract: To understand the effect of cavitation on the flow acoustics of a low specific speed centrifugal pump, this study examines the characteristics of pressure fluctuation and flow noise under different cavitation numbers by combining numerical simulations with experimental measurements, focusing on analysis of the frequency domain characteristics of pressure fluctuations and the frequency responses of sound pressure at typical positions. The results show that as cavitation develops, low-frequency broadband fluctuations in the pump are intensifying. At critical cavitation, the 1/6 rotation frequency becomes dominant in pressure fluctuations at impeller inlet and in the volute region it becomes a significant secondary frequency while the blade passing frequency remains dominant. Pressure fluctuations caused by rotor-stator interaction is the major source of flow noise, and noises induced by cavitation are broadband concentrating on a high-frequency band of 1000-2000 Hz. As cavitation develops, the sound pressure level at the characteristic frequency drops under the action of impeller rotating dipole sound source while it rises under the action of volute dipole sound source, and the characteristic frequency at the high harmonics of blade passing is gradually submerged in a high-frequency broadband. This study lays a basis for further study of the flow and sound behaviors and for reduction of cavitation vibration and noise in low specific speed centrifugal pumps.

Key words: low specific speed centrifugal pump, cavitation, pressure fluctuation, noise, broadband frequency