Tone Generation by Flow Past Deep Wall Cavities

Flow past deep wall cavities exhibits strong interaction with the standing wave system in the cavity. The shear layer separating the exterior flow from the cavi ty flow supports i nstabil iti es which excite the normal cavity modes. In turn, the cavity wave system reirlforces the instabil i ­ ties. Experimental studies have shown that two distinct instability modes are encountered as the external velocity is increased. The pressure coeffi ci ent versus Strouha1 number behavi or re­ veals two maxima which correspond to different instability modes of the shear layer. Flow vis­ ualization studies have shown that these modes correspond to di st i nct shear 1ayer vortex struc­ tures. At high velocities, single large-scale vortices are formed on the interface. At lower velocities, two vortices are present, simultan­ eous ly.