Flow in the Wake of a Cascade of Oscillating Airfoils
A study has been made of the amplitude and phase of the vertical osciUations in the wake behind 1) a cascade of airfoils oscillating in phase and 2) a cascade of airfoils at zero incidence with oscillating flaps. It was found that in both cases the amplitude of the flow oscillations in the wake remained approximately constant downstream for the values of frequency parameter and airfoil spacing considered. From the results of some preliminary experimental work it appears that sinusoidal gusts could be reproduced in an open jet wind tunnel fitted with either system, but the second type of airfoil-flap arrangement is preferable in practice. The difficulties resulting from flow separation and early stalling which arise with the first system do not appear until much higher angular amplitudes are used when only the flaps are oscillated.