[Paper Review] Gasdynamic Diode: How to Stop 100-kV Streamer

N. L. Aleksandrov|arXiv (Cornell University)|Apr 11, 2019

Plasma Applications and DiagnosticsMedicine26 references3 citations

TL;DR

This paper proposes a gasdynamic diode mechanism that blocks 100-kV streamers by exploiting a neutral gas density discontinuity across a shock wave. Using 2D numerical simulations, it shows that streamers fail to penetrate into high-density regions when the density ratio exceeds 1.2, instead propagating along the interface, demonstrating unidirectional conductivity in transient plasma discharges.

ABSTRACT

The conditions were found when the gaseous medium demonstrates a unidirectional conductivity on a short time scale; a gas density discontinuity forms a kind of gas-dynamic diode that allows the plasma channel to propagate in one direction and blocks its development in another. The results of a two-dimensional numerical simulation of a streamer discharge developing through a shock wave in air were presented for various neutral density discontinuities across the wave. The focus was on the case when the streamer propagated from a low density region to a high-density region. Streamer characteristics changed greatly after intersecting the shock wave. It was shown that the streamer failed to penetrate into the high-density region when the ratio between the densities in these regions was sufficiently high (> 1.2). In this case, the discharge developed along the surface between these regions after reaching the boundary between them. Streamers could penetrate into any of the high-density and low-density regions when a neutral particle density discontinuity was replaced by a gradual density change.

Motivation & Objective

• To investigate the conditions under which a gaseous medium exhibits unidirectional conductivity on a short timescale.
• To understand how shock wave-induced neutral density discontinuities affect streamer discharge propagation in air.
• To determine the critical density ratio at which streamer penetration into high-density regions is blocked.
• To explore the transition from abrupt to gradual density changes and its impact on streamer behavior.

Proposed method

• Conducting two-dimensional numerical simulations of streamer discharge development through a shock wave in air.
• Modeling the streamer dynamics across a sharp neutral density discontinuity formed by a shock wave.
• Varying the density ratio between low- and high-density regions to assess its effect on streamer propagation.
• Analyzing streamer characteristics such as velocity, morphology, and propagation direction after crossing the shock front.
• Comparing results for abrupt density discontinuities versus gradual density transitions.
• Tracking the evolution of the plasma channel to identify blocking or lateral propagation behavior.

Experimental results

Research questions

• RQ1 Under what conditions does a gas-dynamic diode effect emerge in a streamer discharge due to a shock wave?
• RQ2 What is the critical density ratio above which streamers fail to penetrate into the high-density region?
• RQ3 How does the streamer behavior change when the density discontinuity is replaced by a gradual transition?
• RQ4 What determines whether the streamer propagates into the high-density region or is blocked and redirected along the interface?
• RQ5 How does the shock wave influence the unidirectional conductivity of the plasma channel?

Key findings

• When the density ratio between low- and high-density regions exceeds 1.2, streamers fail to penetrate into the high-density region.
• Instead of penetrating, the streamer propagates along the interface between the low- and high-density regions after reaching the boundary.
• The streamer discharge exhibits unidirectional conductivity due to the asymmetric response to the density discontinuity.
• The blocking effect is absent when the density discontinuity is replaced by a gradual density change, allowing streamer penetration in both directions.
• Streamer characteristics, including velocity and morphology, change significantly after crossing the shock wave.
• The gas-dynamic diode mechanism enables controlled plasma channel development in one direction while blocking it in the opposite direction.