Effect of Adverse Pressure Gradient on Surface Plasma Actuator Viscous Drag Reduction*

An active surface Pulsed-DC plasma actuator array that has shown the ability to reduce viscous drag by as much as 70% in zero pressure gradient turbulent boundary layers is investigated under adverse pressure gradients. The actuator is designed to produce a spanwise velocity component to suppress the lift-up of near-wall “streak” structures which have been correlated with the wall shear stress. The experiments are performed on a suspended plate with a pivoting trailing portion over which the adverse pressure gradient is developed. The surface actuator is located in the pivoting plate on a floating element on which the viscous drag is directly measured. The boundary layer measurements include mean velocity and turbulence intensity profiles, velocity spectra, and “burst” statistics based on a VITA method. The results are contrasted with those of the equivalent zero pressure gradient turbulent boundary layer.