Wind tunnel experiments of long arcs in crossflow: Cathodic roots and scaling
Researchers in the Aerospace Plasma Group along with European collaborators conducted experiments involving lightning sweeping across an airplane’s surface in the Wright Brothers Wind Tunnel, using diagnostics to better understand how an electrical arc and its surrounding airflow interact with each other.
Authors: Fayleon Lin, Vincent Andraud, Guillem Tobella, Joan Montanya, Rafael Sousa Martins and Carmen Guerra-Garcia
Citation: Journal of Physics D: Applied Physics. 2026
Abstract:
This paper presents an experimental investigation of the properties of long electrical arcs immersed in a crossflow. The insights gained from these experiments can be applied in numerous fields: one of which is lightning protection of aircraft. Upon initial attachment to the airplane, the lightning arc column can sweep along the plane’s surface due to the relative motion between the two in a process known as the swept-stroke.
The first set of experiments corresponds to meter-scale low-current D.C. arcs (3 A) attaching to an aeronautic airfoil in low speed flow (1–4 m s−1), extending prior work that considered an anodic airfoil to the negative polarity case. The dynamic and electrical properties of the arc channel, as well as the dynamic motion of the cathodic arc root, are investigated through high-speed imaging, particle image velocimetry, and electrical measurements. The influences of wind speed, airfoil angle of attack, and counter-electrode configuration are explored.
The second set of results applies the same data processing to high-speed videos from a previous experimental campaign conducted at ONERA on meter-long high-current D.C. arcs (200–600 A) subject to high-speed flow (40–60 m s−1). Unlike the anodic arc root, the cathodic arc root is observed to either stall or sweep along the airfoil surface. In general, the root trails the leading edge of the arc column, which is advected by the flow, with the degree of lag depending on the experimental conditions. These findings enable analysis of how flow separation, boundary layer dynamics, arc regimes, and cathode emission processes influence the physical behavior of the arc column and root over two orders of magnitude in current and one order of magnitude in wind speed, providing insight into the coupled phenomena governing the swept-stroke.
