Dynamics of Long Electrical Arcs in Crossflow: An Imaging Study

A lightning strike delivers hundreds of amps of steady current while attached to an aircraft. Although airliners are struck by lightning around once a year, the industry remains safe thanks to appropriate lightning protection systems. Current protection guidelines are based on prior service experience and historical data, which might be inadequate for next-generation aircraft with novel and unconventional aircraft designs. Thus, new proposals suggest incorporating design methods aided by numerical simulation modeling the behavior of lightning attachment and the subsequent swept-stroke phase. Experimental data, under relevant conditions, is scarce and is needed to build and validate local models of the arc-attachment process that account for the interaction with the flow, the surface and material properties, as well as the polarity of the arc. The current collaboration between MIT, ONERA, UPC, and ISL aims to fill this gap by investigating the fluid-arc coupling quantitatively through measurement of both the arc dynamics and the fluid dynamics. For now, long arcs up to 80 cm in length and 3 A in constant current are subjected to different geometric, electrical, and fluid flow conditions with plans for more realistic conditions in the future. The arcs are characterized by time-resolved current and voltage readings and high-speed videos. The 2D fluid velocity field is obtained using particle image velocimetry. In-house algorithms accurately track the arc column motion to obtain detailed statistics of the column and the root behavior, along with a joint velocity visualization of the arc and the flow.