Wind Tunnel Experiments of Long Arcs in Crossflow: Anodic Roots and Influence of Flow Field

This paper presents an experimental investigation into the dynamics of long electrical arcs attached to an airfoil immersed in crossflow. The arcs are D.C., with around 3 A current and up to 1 m in length. Diagnostics include simultaneous high-speed video imaging of the arc column and root, particle image velocimetry (PIV) measurements of the flow velocity field, and electrical measurements of arc voltage and current. The study focuses on an anodic airfoil polarity, with variations in wind speed (1-4 m/s), angle of attack (0-20 degrees), and different cathode-electrode configurations (ball and rail). Experimental results reveal that, for smaller angles of attack and higher wind speeds, the arc root adopts a `jumping' behavior along the airfoil, while separated flow at higher angles of attack tends to stagnate the root near the separation point. Despite significant arc elongation and tortuosity induced by the flow, the instantaneous value of the arc's internal electric field aligns well with values for free-burning arcs reported in the literature. PIV and optical-flow analyses further indicate that the arc column is advected nearly at the local flow speed, highlighting the strong coupling between arc behavior and flow environment.