Organized oscillations of initially turbulent flow past a cavity

The unsteady Bow structure due to a turbulent boundary layer past a rectang ular, open cavity is characterized using a cinematographic technique of hig h-image-density particle image velocimetry. Organized small- and large-scal e vortical structures emerge above the turbulent background in absence of m echanisms that typically enhance the organized nature of such shear flows: acoustic resonance, Mach wave reflections, and elastic effects of the cavit y boundary. The large-scale vortical structures induce ordered pressure flu ctuations at the impingement corner of the cavity; their magnitude and phas e shift are characterized using simultaneous imaging and pressure measureme nts. Within the cavity, a jetlike Bow occurs along the cavity walls, and it eventually modulates the separating shear layer at the leading corner of t he cavity. The nature of this wall jet Bow is a function of the impingement process at the trailing corner of the cavity. Calculation of the turbulenc e statistics based on Bow images reveals that the turbulence in the separat ed shear layer along the mouth of the cavity and in the jetlike flow within the cavity rapidly dominate the turbulent structure of the inflow.