Acoustic emission characteristics of underwater gas jet from a horizontal exhaust nozzle

The sound spectrum generated by steady gas jet from a submerged horizontal nozzle was experimentally investigated to analyze the acoustic emission characteristics. The effects of gas velocity in the range of 35–140 m/s on the sound spectrum were investigated. The results indicate that increasing gas velocity elongated and strengthened the bubbles and increased the acoustic emission. However, the noise was mainly of low frequency, the peak values of the noise level occurred below 2 kHz in all the gas velocities considered in the tests. A theoretical model incorporating conditions after bubble detachment was developed to explain the experimental result. The noise prior to bubble detachment is ignored for steady gas flow and isothermal gas–water system. Although the comparison with the experimental results was qualitative, the model predictions clearly demonstrated the low-frequency characteristics of underwater gas jet noise.