Evolution of stratification instability seeded by resistive inclusions in electrically exploding wires

Abstract

Numerical investigation on the evolution of stratification instability seeded by resistive inclusions in electrically exploding aluminum wires is reported. The resistive inclusions at the submicrometer scale create hot spots with enhanced Joule heating during the first phase of electrical explosion in the wires, amplifying the peripheral current density. The temperature rise of a hot spot first increases and then decreases with resistivity. The hot spot reaches its maximum temperature rise at 70-times the aluminum resistivity. Exploding products ejected from localized hot spots pile up on both sides of the seeding regions. Perturbations in the front edge of the dense core emerge after several tens of nanoseconds. Bright stripes are formed inside out, providing a possible explanation for the absence of stratified structures at the very beginning of discharge. A numerical shadowgram is reconstructed using a flow visualization technique. The matching of the numerical shadowgram and experimental shadowgram indicates that the resistive inclusions characterized by increased resistivity comprise an important seed in stratification instability. This study helps in understanding the seeding mechanism of electrothermal instability in pulsed-power-driven plasma systems.