Vortex rings drive entrainment and cooling in flow induced by a spark discharge

TL;DR

This study models how vortex rings generated by spark discharges entrain cold air and cool hot gas kernels, revealing the dynamics of plasma-induced flows through experimental validation.

Contribution

The paper introduces a new model describing vortex ring-driven entrainment and cooling in spark-induced flows, supported by experimental measurements.

Findings

Vortex rings' radial expansion correlates with electrical energy deposited.

Entrainment and cooling are primarily driven by vortex rings.

Cooling rate increases with energy deposited during spark discharge.

Abstract

Spark plasma discharges induce vortex rings and a hot gas kernel. We develop a model to describe the late stage of the spark induced flow and the role of the vortex rings in the entrainment of cold ambient gas and the cooling of the hot gas kernel. The model is tested in a plasma-induced flow, using density and velocity measurements obtained from simultaneous stereoscopic particle image velocimetry (S-PIV) and background oriented schlieren (BOS). We show that the spatial distribution of the hot kernel follows the motion of the vortex rings, whose radial expansion increases with the electrical energy deposited during the spark discharge. The vortex ring cooling model establishes that entrainment in the convective cooling regime is induced by the vortex rings and governs the cooling of the hot gas kernel, and the rate of cooling increases with the electrical energy deposited during the spark discharge.