Experimental study of cavity flow oscillations with upstream mass-injection

Cavity flows are encountered in a wide range of applications in which large flow and pressure oscillations often occur. In weapon bay applications, these oscillations, which have been associated with the shear flow across the cavity, are of great concern when carrying and separating stores. The purpose of this investigation is therefore to use mass-injection ahead of the cavity to alter the shear flow across the cavity to reduce or eliminate cavity oscillations. At first, a review and analysis of cavity flow, shear layer flow and mass-injection is presented. Then, the results of an experimental study performed at the University of Tennessee Space Institute supersonic wind tunnel with an 8 in. square test section are provided. Significant attenuation of cavity oscillations was observed experimentally with upstream mass-injection. The thickening of the cavity shear layer alters its stability characteristics such that its preferred frequency of oscillations falls outside of the natural frequencies of the cavity. As a result of the experimental investigation, it is concluded that mass-injection is effective in reducing cavity oscillations; and it is recommended that a fundamental parametric study be undertaken.