Target Strength Observations of Wobbly Bubbles

TitleTarget Strength Observations of Wobbly Bubbles
Publication TypeConference Abstract
AuthorsPadilla, AM, Rychert, KM, Weber, TC
Conference Name171st Meeting of the Acoustical Society of America
Conference LocationSalt Lake City, Utah
Conference DatesMay 23-27
KeywordsAcoustic Scattering; Gas Bubbles;

Large methane bubbles released from shallow water seabed are of interest because bubbles facilitate the transport process of gas through their journey in the water column, making them more susceptible to reaching the atmosphere than those released from deep water. Several models that relate bubble radius and acoustic backscattering for ideal, spherical bubbles have been developed and are typically used by researchers attempting to invert acoustic backscatter measurements for bubble size and/or gas flux. However, based on theory and field experimentation, it has been shown that large free gas bubbles in liquids (large Eötvös and/or large Reynolds numbers) are non-spherical. A shallow water (< 6 m) tank experiment has been designed to understand the influence of bubble shape on acoustic backscattering. This experiment was conducted for bubbles between 1-5 mm in radius (Eötvös number between 0.5 and 13, Reynolds numbers between 300 and 1500, and a Morton number of approximately 7.2e-11) and at frequencies between 10-100 kHz. These frequencies are well above bubble resonance but cover the range of typical echo sounder measurements of bubbles in the field. Calibrated bubble target strength for these bubbles will be compared to existing acoustic backscattering models for bubbles.