The present study investigates the lift gains and losses generated by the superposition of a periodic spanwise-synchronous and spanwise-varied actuation component onto a steady component on an airfoil with a highly deflected Coanda flap. The unsteady actuation is provided by 33 specially-designed lip segments that deliver actuation frequencies up to 300 Hz and actuation amplitudes up to 100% of the mean blowing intensity. The results demonstrate the benefits of superimposing a periodic spanwise-synchronous component onto the steady actuation component for a separated or partially-attached flow, where up to ΔC_1 = 0.2 lift increase is achieved. Square wave motion is shown to be more robust than sinusoidal motion with a broader lift gain region. Spanwise traveling wave yield the highest lift gains with ΔC_1 = 0.25 with a relatively slow wave frequency and long wavelength. Machine learning control has also been successfully implemented with promising initial results.
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