Effects of an annular plasma actuator on a co-flow jet downstream of a bluff-body

Abstract

The present study is to experimentally investigate flow interactions downstream of a bluff-body incorporated with an annular plasma actuator, potentially for flame stabilization application. The dielectric-barrier discharge (DBD) actuator, flush with the bluff-body, is operated with AC in both sine and square waves, creating an inward flow and facilitating air entrainment to the jet. Electrical measurements show the larger peak current and the higher dissipation power in square wave, in which the high variation rate of voltage favors the electron escape from the dielectric surface, resulting in a stronger discharge. In addition, a more diffusive discharge accompanied with a larger peak current is observed in the negative half-cycle while filament discharges are present in the positive half-cycle. The plasma-induced flow is confirmed to be positively charged due to the flow deflection in a lateral DC electric field. Schlieren imaging and particle image velocimetry (PIV) show that as the actuator is activated, the jet at low Reynolds number is more susceptible to develop into turbulence and a vortex ring, due to the secondary low-pressure region induced by the actuator, is formed downstream of the bluff-body. The vortex ring is advantageous to active flow control, and is shown to enhance flame stabilization.