Evolution of a shock wave generated by underwater electrical explosion of a single wire

The results of an experimental, analytical, and numerical study of the cylindrical shock wave generated by the underwater electrical explosion of copper and aluminum wires are reported. Experiments were conducted using a microsecond timescale generator delivering ∼180 kA pulses with a 1.2 μs rise time. Shadow streak images were used to study the radial expansion of the exploding wire and the generated shock wave. It was found that the shock wave expansion velocity decreases to the velocity of sound in two stages: a fast stage and then a gradual stage. The fast stage occurs during ∼1.5 μs after the maximum of the resistive voltage is reached, and then, a gradual decrease occurs during several tens of microseconds. It was shown that the duration of the fast stage corresponds to the period of time when the main energy deposition into the wire occurs. Hydrodynamic simulations show that the fast decrease in the shock velocity is related to the evolution of the exploded wire's subsonic expansion, which leads to...