Rayleigh conductivity and self-sustained oscillations (Q1390027)

We discuss the theory of self-sustaining oscillations at low Mach number, high-Reynolds-number shear layers, and jets impinging on edges and corners. Such oscillations generate narrow band sound, and are usually attributed to the formation of discrete vortices whose interactions with the edge or corner produce impulsive pressures that trigger the cyclic formation of new vorticity. A linearized analysis of these interactions is described in which free shear layers are treated as vortex sheets. Details are given for shear flow over wall apertures and shallow cavities, and for jet-edge interactions.