Measurement of the waveform parameters of shallow explosive charges

Abstract

Measurements of the properties of shallow underwater explosions have been obtained in recent experiments with 0.82-kg SUS (signal underwater sound) charges at depths from 23.5 to 194.5 m. The data were recorded in the farfield with a high-resolution digital recording system to ensure good reproduction of both the high- and low-frequency components of the waveform. The measurements provide new results for the pressures, impulses, durations, and time constants of the shock wave and the first bubble pulse, and in addition, extend the available information to include the properties of the subsequent bubble pulses and the negative phases. Comparison of the data with previously published semiempirical relationships based on experiments with deeper charges indicates that those expressions generally do not provide adequate descriptions of the shallow charge data. In particular, there is significant disagreement with the measurements of the shock wave decay constant, and with the measurements of all of the bubble phase properties. The effect of vertical migration is appreciable for shallow charges and was observed in the measurements of bubble pulse periods, pressures, and impulses. Semiempirical relationships were derived from the data for the properties of both the shock wave and the bubble pulse series. These expressions account for the depth dependence due to migration observed in the bubble phase properties and consequently provide parameter values appropriate for modeling the pressure waveform of shallow charges.