Characterization of Tollmien-Schlichting Wave Damping by DBD Plasma Actuators Using Phase-Locked PIV

Abstract

A phase averaged optical measurement technique is used for characterization of externally excited boundary-layer disturbances. Two-dimensional velocity fields of flat-plate boundary-layer flow are recorded via Particle Image Velocimetry to resolve the effect of Dielectric Barrier Discharge plasma actuators on Tollmien-Schlichting waves. These are artificially excited by a vibrating disturbance source flush-mounted with the surface of the flat plate. A delay-generator is used to trigger the image acquisition on predetermined phase angles of the excitation frequency. Phase averaging unveils the temporal and spatial evolution of the boundary-layer disturbances. Characteristics of the excited waves are quantified and compared to linear stability theory. The phase-locked technique allows the evaluation of plasma actuation on the excited waves. A reduction of the wave amplitude by 26% was recorded for a continuously operated, single Dielectric Barrier Discharge actuator. A comprehensive investigation of the actuator effect under variable flow velocities and pressure gradients is presented in this manuscript.