Flow noise analysis based on experiment data of submerged buoy during the falling process

The flow noise generated during the descent of the vertical line array (VLA) reduces the signal-to-noise ratio (SNR) of the hydrophone, which degrades its ability to detect the weak signal. This paper focus on analyzing the flow noise generated during the descent of the VLA. The simulated flow noise was calculated using the wavenumber-frequency spectrum analysis method, which is based on Carpenter's turbulent boundary layer pressure spectrum. The measured flow noise was obtained from a deep-water experiment in South China Sea, 2016. The simulation result shows that the energy of the flow noise is mainly distributed in low frequency band, and the energy will increase and spread to high frequency band with increasing stream velocity. The experiment result indicates that the energy of flow noise is concentrated in low frequency band when the stream velocity is 1.2 m/s. At the frequency of 20 Hz, the noise level of the received data is 11.5 dB higher than that of the underwater ambient noise. These findings are beneficial for active sonar array signal processing.