SELF-SUSTAINED OSCILLATIONS OF IMPINGING FREE SHEAR LAYERS

Since the observation of the edge-tone phenomenon by Sondhaus in 1854, self-sustaining oscillations have been observed for a wide variety of shear-layer impingement configurations. These oscillations are the source of flow noise and undesirable structural loading, and occur in a range of applications that includes transonic wind tunnels (Woolley & Karamcheti 1973, McCanless & Boone 1974), aircraft components (Heller & Bliss 1975, Evertz et al 1976), slotted flumes (Betts 1972), high-head gates (Martin et al 1975), velocity probes (Hussain & Zaman 1977a,b), and pressure probes (Michalke et al 1974). Despite the apparent differences between these types of oscillations, they exhibit several common characteristics, which, when critically examined, will hopefully lead to a better understanding of the underlying mechanisms.