On the experimental full scale vibrational response analysis of a large pleasure yacht

This paper presents an experimental investigation carried out on a large pleasure yacht during a sea trial using vibration signal processing methods to characterize its dynamic operational behaviour and to identify contributions of the main sources acting on the system including the onset of the propeller cavitation phenomenon. Synchronous averages were computed to isolate vibration components associated with a specific source acting on the system. Their use jointly with variance computation allowed the detection of the rise of cavitation. Spectral Kurtosis analysis suggested optimal-bandwidth of the filter for system response demodulation and so better identify the rise of high frequency energy of bursting contents induced from cavitation strictly linked to propeller rotation. Cyclic modulation spectrum was also adopted, which allows to extract the modulation features of cyclostationary signals, shows the rise of an interaction between high frequency contents and blade passage phenomenon approaching cavitating condition. The results seem to provide an interesting solution based on the vessel vibrational response to define source contribution to the targets for a better identification of the dynamic system. Moreover, the proposed diagnostic methods reveal reliable tools for real time condition-based monitoring of the marine propeller to distinguish cavitation and wake energy contribution using vibrational response measured on the hull instead of hydrophone arrays.