The use of self-resonating cavitating water jets for underwater sound generation

Abstract

A self-excited cavitating jet assembly is examined for possible use as an underwater noise generator. The principles of the system are based on matching the natural frequency of a submerged jet with that of a resonant chamber through a feedback mechanism. The case of an organ pipe resonant feed tube is thoroughly investigated. In this case, feedback is obtained by shaping the nozzle in order to optimize its interaction with instabilities in the shear layer of the jet. The performance of the noise generator is evaluated and its characteristics analyzed, including the influence of the pressure drop across the nozzle, the cavitation number, and the organ pipe length. It is observed that the efficiency of STRATOJETs (self-resonating cavitating jets) is more than two orders of magnitude higher than that of a conventional cavitating jet. The knowledge developed in this study allows for selection of the amplitude and frequency of the emitted noise by proper dimensioning of the assembly and correct choice of the functioning conditions.