The bubble pulse on deep fired/long-range underwater explosion records

Abstract

Many years ago, the author analyzed a representative deep-fired/long-range underwater explosion record [J. Acoust. Soc. Am. 35, 800 (1963)]. The most striking feature was the so-called “double shock” formation, e.g., a strong resemblance between the shock wave and bubble pulse in both amplitude and shape. The phenomenon is attributed to the combined effects of detonation depth and waveform propagation. Recently [Proc. 11th Intern. Congress Acoust., Paris, 1983, Vol. 1, pp. 345–348] the characteristics of an explosion waveform at the source, as a function of firing depth was established. Here, weak shock theory is used to study the nonlinear distortion of the bubble pulse as it propagates. The criterion for shock wave formation depends inter alia on the strength and duration of the pulse. Pulse amplitude increases slowly, but its duration decreases rapidly, with charge depth. It is found that the shot depth plays the crucial role and that consequently the deep fired shots suffer the greatest distortion, tending towards shock wave formation at long range.