Abstract
Various underwater full-scale steam-exhaust configurations were investigated. The greatest sound-pressure level (SPL) was obtained with steam pulsed through a long tube, i.e., with a length/diameter ratio>10. This intermittent technique generated a collapsing, coherent bubble that produced a SPL 50 dB higher than that obtainable with modulated steady-state flows. For example, the peak presure, near the surface, with a 4-in.-diam nozzle was from a 14-ms acoustic impulse having an on-axis SPL of 141 dB//1 μbar/1 yd. Air injection causes damped oscillations. A water-hammer phenomenon was observed with significant acoustic power output. Oscillograms and movies were made of the bubble phenomena. [Work supported by the U. S. Office of Naval Research.]
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