Acoustic radiation of a flow-excited circular cylinder: experiment-informed modelling and receiver-side transfer-path characterisation

The underwater acoustic radiation of vibrating cylindrical structures is of practical importance in offshore engineering, pipeline monitoring, and underwater noise control. In the present study, an experiment-informed reduced-order hydro-vibro-acoustic framework is developed to describe the pathway from hydrodynamic excitation to structural response and finally to radiated sound. The hydrodynamic forcing model is parameterised using stationary-cylinder measurements, while the structural dynamic characteristics are obtained from free-vibration measurements of an elastically mounted cylinder. The resulting structural response is used to determine the wall-normal vibration velocity, which then serves as the input to an acoustic radiation model in the frequency domain. In this way, the chain from excitation to vibration and acoustic radiation is represented within a unified reduced-order framework. An independent underwater cylindrical-shell experiment is further introduced to characterise the receiver-side vibration-to-pressure transfer behaviour under controlled harmonic excitation.In that experiment, shell vibration responses and hydrophone pressure signals are measured simultaneously under harmonic excitation from 100 to 5000 Hz. Frequency-domain analyses, including power spectral density, sound pressure level, narrowband peak extraction, coherence, frequency response function, and a local vibration-to-pressure transfer indicator, are performed to characterise the measured vibration-to-pressure relationship. The results show that the dominant vibration and hydrophone-pressure peaks are closely aligned in frequency, with deviations of <0.3 Hz under the tested harmonic-excitation conditions. High coherence values, generally close to unity at the excitation frequencies, indicate a strong linear association between the measured local shell vibration and hydrophone pressure under deterministic harmonic excitation. The experimentally derived vibration-to-pressure transfer function further exhibits a clear frequency dependence. In addition, the local vibration-to-pressure transfer indicator varies markedly with frequency, showing that the measured pressure response cannot be inferred from the local vibration amplitude alone. The shell experiment therefore provides an independent experimental characterisation of the receiver-side vibration-to-pressure transfer path, rather than a direct validation of the acoustic-radiation model for the flow-excited cylinder. Accordingly, the modelled acoustic response of the flow-excited cylinder is interpreted as an experiment-informed estimate whose trends, rather than absolute sound-pressure levels, are the primary focus of the present study.