Temporally and spatially resolved spectroscopic measurements of plasma actuator thermal properties

The potential of plasma actuators for high-speed flow control has motivated significant recent research, particularly focusing on the physics and applications of localized arc filament plasma actuators (LAFPAs). In an effort to better understand the physics behind the volumetric gas (Joule) heating effect that results in the flow actuation of the LAFPA, the thermal properties of the plasma were investigated by employing high-resolution, time-resolved and low-resolution, spatially-resolved spectroscopy. The high-resolution, time-resolved experiments yielded a temperature history over the duration of a plasma pulse. The rotational and vibrational temperatures of the N₂ in the plasma were seen to rise significantly as the pulse progressed despite the most intense emission coming from the early times in the pulse. The low-resolution, spatially-resolved experiments characterized the behavior of four key excited species in the plasma during a pulse: atomic tungsten, NO, N₂, and OH. Significant spatial variation and evolving spectral features were demonstrated within the first microsecond of the pulse.