Model scale noise measurements of the research vessel Nawigator XXI propeller

• Results of extensive model scale noise measurements of the Nawigator XXI propeller are presented • Noise spectra correlate with cavitation inception, extent and behaviour • Insufficient amount of cavitation nuclei causes strongly intermittent cavitation, affecting noise measurements • Effects of cavitation intermittency on results of noise tests are mitigated by a post-processing method In the last decades, the prediction and mitigation of ships underwater radiated noise have become an important matter of study for research institutions in naval hydrodynamics, mostly because of the adverse impacts that anthropogenic noise may have on marine ecosystems. Propellers are commonly recognized as the main noise sources, when cavitating, therefore large effort is dedicated to the prediction of propeller cavitation and noise. Model scale noise measurements represent the oldest approach to perform this task, and its effectiveness is generally rather good. Yet the extrapolation of full scale noise from model tests presents many challenges associated to the many scale effects involved, as well as the effects of the adopted facility and experimental procedure. In this framework, the availability of comparisons between model test results and sea trials, as well as comparative studies among various facilities is of utmost importance to define and improve proper testing and scaling procedures for cavitating propeller noise. This work presents the results of the extensive experimental campaign carried out at the University of Genova cavitation tunnel on the model propeller of the research vessel Nawigator XXI. This propeller will be the object of the Round Robin test program planned within the International Towing Tank Conference, therefore current work will provide valuable information on this important test case in the view of future analyses and comparisons.