The dynamics of discontinuities in a cylindrical energy deposition based on a nanosecond discharge

TL;DR

This study experimentally visualized the complex dynamics of shock waves and discontinuities during a nanosecond high-current discharge in air, revealing detailed flow structures and shock focusing phenomena.

Contribution

It provides the first detailed high-speed visualization of cylindrically symmetric shock and contact discontinuities during nanosecond discharges in air.

Findings

Visualization of shock wave propagation and contact discontinuities.

Observation of shock wave focusing and formation of a heated cord.

Identification of different gas-dynamic discontinuities in the discharge process.

Abstract

The focusing of a secondary shock wave was experimentally recorded during the implementation of an extended nanosecond high-current discharge of a cylindrical configuration in air. Using high-speed shadowgraph recording (up to 300 000 frames/s) of the emerging unsteady flow, cylindrically symmetric gas-dynamic discontinuities were visualized: a diverging shock wave moving from the discharge plasma boundary, a diverging contact discontinuity separating the shock-heated gas from the nonequilibrium region excited by the discharge plasma, and also a converging compression wave (secondary shock wave) moving from the contact surface to the axis of symmetry and focusing on it 50-60 microseconds after discharge with the formation of a heated long-lived cord.