On the Shape Evolution of Underwater Explosion Bubbles by Cylindrical Charges

Oscillation images of underwater explosion bubbles generated by cylindrical PETN with length to diameter ratio from 3.35 to 6.75 are conducted in a water tank by using high-speed photography technology. Bubble shape evolution is investigated by involving real detonation processes and Rayleigh-Plesset function. Results show that the initial bubble has an asymmetric shape, and the asymmetry is enhanced as the length to diameter ratio increases. The bubble-water interface expansion motion at the side of the charge exhibits an exponential decay, while along the charge axis the decay tends to piecewise linear, both differ from the Rayleigh bubble. These differences are potentially attributed to the asymmetric energy structure of cylindrical charge, which is similar to the usable energy distribution of a cylindrical charge underwater explosion shock wave.