Closed-loop vectoring control of a turbulent jet using periodic excitation

Closed-loop active flow control strategies were studied experimentally using periodic excitation in order to vector a turbulent jet. Jet deflection was achieved by attaching a short, wide-angle diffuser at the jet exit and introducing periodic excitation from a segmented slot around the circumference of the round turbulent jet. Conventional and modem control methods were applied in order to quickly and smoothly transition between different jet vectoring angles. It was found that the frequency response of the zero-mass-flux Piezo-electric actuator could be made flat up to about 0.5kI-I~. However, the jet can optimally respond at 30-5OHn This is still an order of magnitude faster than any conventional thrust vectoring system. System identification procedures were applied in order to approximate the system's transfer function and characterize its open- and closed-loop dynamics. Based on the transfer function, a linear controller was designed that enabled fast and smooth transitions between stationary deflection angles and maintained desired jet vectoring angles under varying system conditions. The linear controller was tested over the entire range of available deflection angles and its performance is evaluated and discussed.