On the utilisation of the coupled-oscillator approach as a surrogate model for sound propagation in the vicinity of bubble groups

Abstract

The presence of bubble curtains have been shown to reduce the level of underwater noise propagation. This is due to the change in density and acoustic-impedance between the group of bubbles and the water. In addition, sound waves can be absorbed and scattered when they interact with bubble curtains. In this paper, it is shown that a mathematical model based on the discrete bubble model (DBM) and utilising the self-consistent coupled-oscillator theory is able to correctly predict the bubble collective resonance frequencies of 1D line, 2-D planar, and 3-D complex bubble cloud configurations. This framework can also accommodate polydisperse-sized bubbles. We use the DBM and conduct modal analysis on common 2-D and 3-D bubble curtain configurations and show that the fundamental modes in both configurations dominated the vibration of bubble curtains when subjected to an external acoustic source. In addition, it is demonstrated that the performance of the bubble curtain is most affected by the changes in the bubble size whereas the variations in inter-bubble spacing had no significant influence.