Active control of turbulent boundary layer using an array of piezo-ceramic actuators

This paper presents preliminary results from an experimental exploration on drag reduction in a turbulent boundary layer using an array of piezo-ceramic actuators. The actuator array consisting of 16 actuators can generate wall-normal oscillations and, given a phase shift between two adjacent actuators, a spanwise travelling wave. A sinusoidal waveform with four different amplitudes was investigated while oscillating in a wide range of frequencies. The preliminary results showed that about 5% reduction in drag could be obtained based on the measurement of a hot-film flush-mounted on the wall. A drag increase up to 20% was also observed when the actuator array worked in large amplitudes and high oscillation frequencies. Investigations are ongoing to use different control strategies such as different actuation signals, spanwise travelling wavelengths and speeds, etc. in order to achieve better results in terms of drag reduction.