Experimental and numerical study on underwater radiated noise of AUV

The wide range use of marine equipment has greatly increased the underwater radiated noise (URN) level, creating more threat to marine life. Autonomous underwater vehicle is one of the solutions to reduce the use of large marine equipment and then decrease the noise. Aiming at the noise control of AUV, this study conducted a far field noise measurement experiment on an AUV working on 10 different conditions, which is rarely measured. The hybrid method, predicting the noise with Lighthill equation based on unsteady flow field data from CFD calculation, is adopted. The results from experiment and simulation indicates that the simulative results are in good agreements with experimental results and the propeller will still generate noise due to the irregular vibration of the propeller, which is about 3-5 dB. With the occurrence of cavitation, the sound pressure level (SPL) increases sharply, and there will be a wide gap between experimental and simulative noise data, owing to the single phase considered in the Lighthill equation. The analysis of the experimental and simulative results highlights the existence of structure excitation noise, ranging from 300 to 500 Hz and the shortcoming of noise prediction of the hybrid method under cavitation stage.