Low-frequency active acoustic response of underwater bubble plumes

Active, low frequency acoustics may provide a method of locating and identifying methane bubble plumes over a large area by exciting radial and column resonances. In this work, a proof of concept experiment was conducted by measuring the active, low frequency response of an air bubble plume at the Lake Travis Test Station at the University of Texas at Austin. Several flow rates, bubble sizes, and plume widths were investigated. The test consisted of insonifying the plumes at two different standoff distances using a low-frequency chirp from 300-2500 Hz. The plume response was much longer in time than originally expected due to resonant ringing. The long-time response was modeled with a finite element model, which predicted the column resonance. This behavior may be able to be exploited for long-range bubble plume identification. [Work supported by ExxonMobil.]