3D Backward-Facing Step Flow Structure Modification with Plasma Actuators

Backward-Facing Step (BFS) shape is a common configuration found in several engineering applications. The turbulent flow structure in the backside of a BFS leads to risky situations. Then, flow control is a useful technique to achieve safe conditions. In recent years, plasma devices have become an interesting technology with high importance for flow control because of non-moving parts, fast time response and low energy consumption. This paper presents the experimental investigation of a set of Dielectric Barrier Discharge (DBD) plasma actuators placed on the rounded edge of a BFS and its capability for flow control by wind tunnel testing. In contrast to the other studies, the behaviour of the plasma actuators in presence of 3D flow over a BFS was investigated. Firstly, a parametric study by analysing the location and the influence of the electrical parameters of the DBD plasma actuator was performed at a freestream velocity of 6 m/s using Particle Image Velocimetry (PIV). It was seen that actuator with -45° wall jet provides the highest flow control at 30 kVpp and 2.5 kHz with a reattachment length reduction of 65.6% referred to plasma off case. This configuration was optimized and compared with a double actuator for a higher velocity (10 m/s). The manufacturing complexity of the double actuator recommends the use of a simple actuator due to the fact that they have similar results, with a 30% of reattachment point reduction approximately at 10 m/s. Anyhow, the results confirm the authority of plasma actuators to modify the flow structure behind a BFS.