Imaging studies of discharges in flowing gases: from microdischarges to lightning arcs*

When investigating electrical discharges for aerospace applications, real-world conditions often deviate from textbook ideals, featuring nonuniform environments with reactive and flowing gases. In these environments, the discharge is affected by the fluid dynamics and experimental diagnostics need to address both the plasma and the background neutral flow. This presentation highlights two examples of plasmas in crossflows for two very different regimes. The first case examines nanosecond repetitively pulsed discharges in flow reactors for combustion and chemical conversion. In this case the plasma reactor is a mm-gap dielectric barrier discharge operating with microdischarges. The dynamics of the microdischarges can be visualized using transparent indium tin oxide electrodes and fast videography. Image processing is used to track the dynamics of microdischarges. The second case represents the interaction of lightning discharges with aircraft during flight. During the damaging current flow phase, the arc dynamically interacts with the fluid boundary layer and undergoes reattachment to new locations – known as the swept stroke. To study the swept stroke, we perform wind tunnel experiments with DC arcs, of current about 3A and inter-electrode gap of 20cm. The arc dynamics is visualized using fast videography, and the fluid dynamics using particle image velocimetry.