Description:
Underwater explosions have been studied intensively in the United States since 1941 [e.g., Cole (1945)]. Research to date primarily focuses on the initial shock and subsequent pressure waves caused by the oscillations of a “gas globe” that is the result of a charge detonation. These phenomena have relatively short timescales (typically less than 2 s). However, as the gas globe rises in the water column and breaks the surface, it leaves behind a residual bubble cloud which has been markedly less studied. A recent experiment measured the spatial and time-dependent acoustic response of the bubble cloud resulting from a charge detonated at 50-ft depth. A directional projector was used to propagate a linear FM (5–65-kHz) pulse through the bubble cloud to an array of hydrophones placed on the opposite side of the charge in order to measure attenuation. This talk will focus on the methods used to estimate bubble density size spectra from the attenuation measurements, those of Commander and McDonald (1991), Caruthers (1999), and Czerski (2009). [Work sponsored by the Office of Naval Research, Code 333.]