Closed-loop control of transonic buffet using active shock control bump

At transonic flight conditions, the buffet caused by the shockwave/boundary-layer interaction can degrade aircraft performance and even threaten their safety. In this paper, a closed-loop control using an active shock control bump (SCB) has been proposed to suppress the buffet on a supercritical airfoil flying at transonic speeds. A closed-loop control law is designed by using the lift coefficient as the feedback signal and using the bump height as the control variable. The unsteady numerical simulations show that the buffet can be effectively suppressed by an optimal combination of the parameters of the control law, namely the gain and the delay time. Furthermore, the buffet control effectiveness is still acceptably constrained by a prescribed maximum bump height, which is believed to be practically important. In addition to being able to achieve both wave drag reduction and buffet alleviation, the active SCB is less sensitive to the parameters of the control law and has a shorter response time in comparison with the reference active trailing edge flap.