An Investigation of Plasma Actuators for Flow Control in a $140^{\circ}$ Bend

An experiment is presented to examine the effectiveness of AC dielectric barrier discharge (DBD) plasma actuators to maintain attached flow around a $140^{\circ}$ bend in a sector of a azimuthal channel. The Mach number at the inlet to the bend ranges from 0.10 to 0.23, and the static pressure ranges from 7 to 22 atmospheres. The plasma actuator is located just upstream of the natural flow separation location. It is designed to produce a net body force that is directed downstream and towards the wall. The requirements and design of the plasma actuator were augmented by a CFD simulation that included the plasma actuator body force vector field. The measurements consist of the static pressure distribution along the outside wall of the bend, and an array of total pressure sensors across the centerline of the exit of the bend. The pressure distribution across the channel showed the desired flattening of the mean pressure profile with increasing AC voltage and frequency that was indicative of a more uniform mass flow profile at the exit of the bend. These confirmed a plasma actuator effect that scaled linearly with the AC frequency, and with AC voltage to a power that is expected from the AC DBD analytical model.