Normal shock wave/turbulent boundary-layer interaction control using ‘smart’ piezoelectric actuators

This paper looks at active control of the normal shock wave/turbulent boundary layer interaction (SBLI) using smart flap actuators. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bleed/suction rate through a plenum chamber. The cavity allows rapid thickening of the boundary-layer approaching the shock, which splits into a series of weaker shocks forming a lambda shock foot, thus reducing wave drag. Active control allows optimisation of the interaction, as it would be capable of either positioning the control region around the original shock position using a series of unimorph flaps or fixing the shock position by controlling the rate of mass transfer. The level of control achieved by unimorph piezoelectric actuators is not large because of small amounts of deflection possible. It is believed that to provide optimal control a piezoelectric material, which can provide greater strain and hence higher amounts of deflection is needed. However, currently such a piezoelectric material is not commercially available.