Methods for predicting the noise of transport vessels propellers

Object and purpose of research. The object of the research is the cavitation noise of transport vessels propellers. The purpose is to analyze and generalize modern research and methods for predicting broadband noise induced by the operation of the transport vessels cavitating propellers. Materials and methods. A review of the research materials (published in the XXI century) on the cavitation noise of transport vessels propellers, in particular broadband noise, as well as the author's own research on the causes and physical aspects of the occurrence of broadband noise is carried out. Based on the Fourier analysis of the time functions of velocities and pressures in the flow near the propeller, the conditions for the occurrence of broadband noise at (4–10)-blade harmonics and the parameters that relate this noise to various types of cavitation on the propeller are found. Main results. A review of recent studies results devoted to the cavitation noise of transport vessels propellers has shown that the levels of the so-called broadband noise that occurs when the cavitating propeller operates in nonuniform flow at high (4–10)-blade harmonics are used as the basis for modern noise predicting methods. At the same time, the authors of the methods consider broadband noise only as a result of the tip vortices development. The paper considers and generalizes an alternative hypothesis of the broadband noise occurrence caused by the occurrence and collapse of cavities within the blade with the formation of a double-headed peak on the time function of pressures. The analysis of publications on the development of the vortex wake behind the propeller and the modeling of pressures at the buckling failure of the tip vortex spirals allowed to show that double pressure peaks can be formed in the flow during the development of the vortex wake behind the propeller. This made it possible to combine both hypotheses of the broadband noise formation – from the development of the tip vortex and from the occurrence and collapse of cavities on the blades – and to link the assessment of the growth possibility of high blade harmonics with the cavitation parameters. Conclusions. It is shown that modern research methods have made it possible to obtain new data on the mechanism of the occurrence and collapse of cavitation both on the blade and in the tip vortex. At the same time, the currently used methods for predicting cavitation and, in particular, broadband noise are very approximate and require refinement to assess the effect of various cavitation characteristics on broadband noise. The hypotheses of broadband noise occurrence and the proposed physical model covering both vortex cavitation and the formation and collapse of cavities can serve as a basis for such clarification.