Enhanced performance of airfoils at moderate Mach numbers using zero-mass flux pulsed blowing

Abstract

Oscillatory wall-jets were introduced through spanwise slots along a flapped NACA 0015 airfoil to establish lift augmentation and drag reduction by the unsteady forcing of the separated flow. Pressure coefficient distributions, lift coefficients, and wake velocity profiles, to determine the drag coefficient, were measured over the test-section speed range of 25m/s between 0.01% and 0.02%, based on RMS velocity, was shown to yield substantially better performance than steady blowing with Cµ in the range 0.5% to 3.5%. In is estimated that steady blowing of at least 10% would be required to reach the same levels of lift coefficient seen with the oscillatory blowing.