Numerical simulation of exploding wires driven by pulsed capacitive discharge

A time-transient simulation code for analyzing underwater wire explosion driven by a pulsed capacitive discharge is developed. It solves a circuit equation coupled with one-dimensional magneto-hydrodynamic equations with the help of appropriate wide-range equation of state (EOS) and electrical conductivity for copper. A modified quotidian EOS model1 is further improved to include the liquid-vapor phase transition which is critical for the generation of shock waves by wire explosion. For the electrical conductivity of copper, a semi-empirical set of equations covering from solid to strongly coupled, partially ionized plasma state2 is utilized. With an appropriate tuning of coefficients appeared in the equation set, an excellent agreement with the experimental results is obtained in terms of temporal motions of a plasma channel boundary and a shock front as well as current and voltage waveforms. It is found that the strength of shock wave generated by wire explosion is greatly influenced by a diameter of the wire and the peak pressure is proportional to the current value at the time of voltage peak irrespective of operating conditions. The numerical model presented in this paper will be utilized not only to optimize the wire explosion system for generating strong shock waves, but also to investigate thermophysical and transport properties of non-ideal plasmas.