Experimental Investigation of Flow-Induced Cavity Resonance

The resonant excitation of a cavity by an equilibrium turbulent grazing flow was investigated. The objectives of the research were first, to understand the dynamic processes related to the shear tones generated by vortex shedding from the upstream edge, and then to determine practical techniques for controlling the excitation and reducing the resonance. Detailed measurements of the cavity pressure and the velocity field in the opening were performed. Spectral data on cavity pressure fluctuations were analyzed over a range of speeds to determine the behavior of both the shear tones and cavity tones during non-resonant and resonant conditions. The cross-spectral properties between the velocity components and cavity pressure were also obtained. The data support the finding that the resonant and nonresonant conditions are distinguished by the behavior of the convection velocity and by the distribution of energy production in the flow field. Techniques for controlling cavity resonance were also investigated. The measurements and data analyses techniques discussed above were also performed for three practical devices. These include a technique, developed by the author, whereby fluid is diverted into the cavity from the boundary layer. The diversion technique is the most effective in reducing cavity resonance.