In a previous study, a series of flow visualization experiments indicated that the classical leading edge vortices on delta wings originate as a series of discrete vortices that are shed from the leading edge at a well-defined frequency. Inspired by the recent attempts to control the growth rate of a free shear layer by perturbing the flow at the end of the splitter plate, a novel method was used in the present investigation to control these discrete vortices. The flow was perturbed by impulsively injecting or withdrawing secondary fluid from a slot along the entire leading edge of a delta wing. The frequency of perturbation and the flow rate from the slot were varied over a wide range. The experiments were conducted in both a water towing tank and a wind tunnel, and flow visualization and velocity probe measurements were used to assess the perturbation effects on the flowfield. The instantaneous velocity signal was used to compute the important statistical quantities of the random velocity field, such as the mean, the root mean square, the spectral distribution, the auto- and cross-correlations, and the probability density function. Over a wide range of Reynolds numbers and angles of attack, the present probe measurements further validated the discrete nature of the leading edge vortices. Moreover, leading-edge perturbations dramatically affected the evolution of the bounded shear layer originating from the delta wing's leading edge. It is found that maximum changes in the leading edge vortices occur when the perturbation frequency is a subharmonic of the natural shedding frequency of the unperturbed wing and when the injection/suction speed is about the same order of magnitude as that of the ambient velocity.
Control of the discrete vortices from a delta wing
Steuerung einzelner Wirbel von einem Deltafluegel
AIAA Journal ; 25 , 8 ; 1042-1049
1987
8 Seiten, 13 Bilder, 17 Quellen
Article (Journal)
English
Control of the discrete vortices from a delta wing
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