Experimental investigation of flow separation delay in S-shaped duct using multiple dielectric barrier discharge plasma actuators

This study experimentally investigates the effects of multiple parallel dielectric barrier discharge (DBD) plasma actuators on controlling the flow separation in an S-shaped duct with an elliptical inlet and circular outlet. An open-loop suction-type test rig composed of composite materials was designed for this purpose. The synergistic effects of multiple DBD plasma actuators (MDBD) were initially examined on a flat plate before being applied to the complex geometry of the S-shaped duct. Additionally, the impact of varying plasma applied voltages (6, 6.5, 7, 7.5, 8 kV) and S-duct inlet velocities (24, 35, and 47 m/s) on the performance of the plasma actuators were investigated. Also, the pressure coefficient distribution on the lower surface of the duct was measured under various conditions. The use of MDBD plasma actuators on a flat plate resulted in a significant increase in the maximum induced velocity, approximately 50 % higher than that achieved with a single actuator. This enhancement is attributed to the synergistic effects of the multiple actuators on the induced flow. The application of the MDBD plasma actuator configuration within the S-shaped duct effectively delayed flow separation across all tested inlet velocities (Reynolds numbers of 2.35 × 10⁵, 3.51 × 10⁵, and 4.75 × 10⁵). However, actuator effectiveness decreased with increasing inlet velocity. Higher actuation voltages resulted in a more pronounced delay in separation. Also, at a Reynolds number of 2.35 × 10⁵, the MDBD configuration with 8 kV and 15 Hz achieved a 35.9 % increase in the pressure coefficient compared to the no-plasma condition.