Control of two-dimensional offset jet using burst modulation with a plasma actuator

An experimental study is performed on a two-dimensional offset jet with a dielectric barrier discharge plasma actuator (PA) as a flow control device that introduces a periodic disturbance to the system. The offset jet is produced by a flow of air emitted from the end of a long parallel channel, and the offset ratio H/h (H: step height, h: channel height) is 1.0. The plasma actuator is installed on the lower wall of the jet exit, and is operated using burst-modulated or continuous waveforms. The Reynolds number based on the mean velocity and the hydraulic diameter of the inlet channel is 2.0 × 103, and the flow at the channel exit is laminar. The wall static pressure and the heat transfer coefficient of the offset plate are measured, and the pressure loss and average Nusselt number are processed. The flow field is examined by flow visualization using a high-speed camera, and the velocity profiles are measured using a particle image velocimetry system. The results show that the reattachment length decreases and the Nusselt number in the recirculation region increases with the induced flow due to the PA. These effects are remarkable at a burst frequency of 100 Hz, which matches the acceptance frequency of the dividing shear layer. At a duty ratio of D = 50 %, due to the existence of a periodic large vortex structure, the reduction of the reattachment length is similar and the Nusselt number is higher compared to those obtained for continuous operation (D = 100 %).