The Mechanics and Acoustics of Bubbles Fragmenting in Sheared Flow.

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Wave-induced bubbles in the upper ocean drive a number of important oceanographic processes including air-sea gas fluxes, aerosol production and the scavenging of organic surfactants. The medium to large bubbles that persist for just a few seconds in the upper ocean during and immediately after wave breaking are thought to play a dominant role in the transport of carbon dioxide. Because it is difficult, for technological and logistical reasons, to make these measurements, there are very few data sets that characterize bubble distributions within whitecaps. Scientists at the Scripps Institution of Oceanography will conduct an experiment whereby bubbles in a turbulent fluid of various sizes will be fragmented. As the bubbles fragment they emit an acoustic signal that will be recorded with hydrophones. In addition, two cameras will record the details of the bubble breakup. The ultimate goal of the research is to determine bubble creation rates at the ocean surface. Although noise is known to come from bubbles as they form, the mechanisms that determine the amount of energy associated with the acoustic oscillations is not yet known. If it were, this work could lead to the development of a tool that allows one to measure bubble creation rates based upon ambient noise measurements. The experiment and data analysis will include the participation of an undergraduate intern.