CONTROL OF FLOW AROUND AN AEROFOIL AT LOW REYNOLDS NUMBERS USING PERIODIC SURFACE MORPHING

Abstract

This thesis investigates the low Reynolds number flow around an aerofoil and its control using periodic motion of the suction surface. Time-resolved measurements reveal the peak-to-peak displacement of the surface motion to be a function of both the amplitude and frequency of the input voltage signal but the addition of aerodynamic forces does not cause significant changes in surface behaviour. The flow around the actuated aerofoil was compared with the unactuated flow. The latter exhibits large separation regions resulting from laminar separation without reattachment. When actuated at 70 Hz, the frequency spectra in the vicinity of the trailing edge and near-wake is dominated by the actuation frequency with sharp peaks suggesting the production of Large Coherent Structures at this frequency. Increased momentum entrainment associated with these enables a significant suppression of the separated region. The result was a simultaneous increase in lift and decrease in drag.