Bluff Body Flow Separation Control using Surface Dielectric Barrier Discharges

Surface dielectric barrier discharges (DBDs) are used to delay flow separation behind a bluff body in atmospheric pressure air. The bluff body is made by connecting a flat plate to a half cylinder tangentially as a round-cornered trailing edge. Four DBD plasma actuators are attached along the surface of the half cylinder. Particle Image Velocimetry (PIV) is utilized for studying the velocity field of the flow. In the first part of the study, flow alteration effects of two different discharge sources – a conventional alternating current (AC) discharge and an ultra short repetitively pulsed plasma discharge (USRD) are compared for identical surface DBD configurations. It is found that, at an identical discharge power (~ 25 W), the AC discharge shows higher ability for flow alteration than the USRD. In the second part, the flow alteration effect of the AC DBD is investigated for varying free stream flow speeds, surface roughness, Reynolds number (Rex), and electrode configuration. The flow speed ranges from 10 m/s to 25 m/s and the corresponding Rex are from 5 × 10 – 5 × 10. In this flow regime, the separation point behind the bluff body can be moved downstream in the presence of the AC DBD. However, it is found that, as the flow speed increases, the separation delay effect decreases. The flow alteration effect also decreases with rougher surfaces and higher Rex. Finally, skewed electrodes and reversed electrodes relative to the flow direction are utilized as two different electrode configurations. It is seen that the skewed electrode provides a positive effect on separation delay while the reversed electrode induces earlier flow separation.