Laminar Boundary-Layer Response to Step Input by an Array of Plasma Actuators

Abstract

Bypass transition is a subcritical transition pathway that a boundary layer may follow from laminar to turbulent state. The latter is associated with higher drag. Prolonging the laminar boundary can therefore enhance efficiency in applications such as the flow over aircraft. Bypass transition is caused by the growth of streaks of low and high velocity in the laminar boundary.Spanwise arrays of plasma actuators have shown promise in experimental demonstrations of the active cancelation of these streaks in an open-loop and also closed-loop feedback control framework to delay transition in the past. However, when the plasma actuators were given a step input to model a fast response to a detected streak, a non-minimum phase response of the far-field velocity and shear stress was detected. Experiments were limited to only the streamwise velocity component and to regions considered in the far fields given physical sensor limitations.