Mathematical verification of dual-frequency characteristic in rotating cavitations

Abstract

© Published under licence by IOP Publishing Ltd.Unlike other common rotating instabilities such as rotating stall, unsteady pressure measurement of inducer rotating cavitation had shown dual-frequency characteristic: the Fourier transformation of the pressure signals showed two distinct frequency peaks. It was assumed that the dual-frequency characteristic is originated from the non-linear interaction between the actual oscillation frequency of the cavity and the blade passing frequency. However, the manifestation of the rotating cavitation as dual-frequency peaks has only been observed experimentally and yet explained theoretically. Thus, based on the oscillating nature of the rotating cavitation, the present paper provides mathematical framework to show that the dual-frequency characteristics can be derived from the phase-locked oscillating cavities. The rotating cavitation is first expressed with respect to the rotating frame, and then transformed into the stationary frame to determine frequency peaks. The predicted frequency peak of the rotating cavitation unsteady pressure signal well captures the experimental results from previous research.