The self-excited oscillating CAVITATION jet nozzle (SEOCJN) serves as a crucial component for converting hydrostatic energy into dynamic pressure energy and ensuring optimal hydraulic and CAVITATION performance of cavitating jets. Thus, it is of crucial significance to understand the CAVITATION characteristics and the influence law of SEOCJN for its extensive industrial applications. This paper utilizes numerical simulation methods to analyze the dynamic process of CAVITATION initiation, development, and outlet CAVITATION performance of SEOCJN. It explores the effects of inlet pressure and flow rate on the frequency characteristics of SEOCJN, and establishes a mathematical relationship between self-excited oscillation frequency and outlet flow frequency. The results indicate that the self-excited oscillation nozzle has an inlet diameter (D1) of 4. 7 mm, an outlet diameter (D2) of 12. 2 mm, a length (L) of 52 mm, a chamber diameter (D) of 83 mm, an oscillation angle of 120°, and an inlet pressure (Pin) of 4. 8 MPa. At these parameters, the frequency of the pulse jet reaches 830. 01 Hz, with an internal flow period of approximately 0. 0024 s. The maximum vapor volume fraction is found to be located 0. 28 m from the outlet of the SEOCJN. Furthermore, the frequency of self-excited oscillation pulse increases with an increase in inlet pressure. These findings provide a theoretical basis for the industrial application of self-excited oscillation CAVITATION jet nozzles

CAVITATION phenomenon can cause deterioration of the hydraulic performance, damage by pitting, material erosion, structure vibration and noise in fluid machinery, turbo-machinery, 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 radiated by a number of configurations in a water tunnel at various operating condition to determine the onset of CAVITATION. The measurements have been conducted over a frequency range of 31. 5 Hz to 31. 5 kHz in one-third octave bands. The onset 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 inception there was a marked rise of the sound pressure level in the high-frequency noise, whilst the low-frequency noise increased 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.

Cogitating flow is investigated around marine propellers, experimentally and numerically. Two different types of conventional model propellers are used for the study. The first one is a four bladed model propeller, so called model A, and the second one is a three bladed propeller, model B. Model A is tested in different CAVITATION regimes in a K23 CAVITATIONs tunnel. The results are presented in characteristic curves and related pictures. Finally, the results are discussed. Model B is investigated based on existing experimental results. In addition, model B is used for validation of the numerical solution prior to the testing of model A. The CAVITATIONs phenomenon is predicted numerically on a two dimensional hydrofoil, NACA0015, as well as propeller models A and B. The CAVITATION prediction on a hydrofoil is carried out in both steady and unsteady states. The results show good agreement in comparison with available experimental data. Propeller models are simulated according to CAVITATIONs tunnel conditions and comparisons are made with the experimental results, quantitatively and qualitatively. The results show good agreement with experimental data under both cogitating and noncavitating conditions. Furthermore, propeller CAVITATION breakdown is well reproduced in the proceeding. The overall results suggest that the present approach is a practicable tool for predicting probable CAVITATIONs on propellers during design processes.