Assessment of Passive Flow Control for Transonic Cavity Flow Using Detached-Eddy Simulation

The implementation of internal store carriage on stealthy military aircraft has accelerated research into transonic cavity flows. Depending on the freestream Mach number and the cavity dimensions, flows inside cavities can become unsteady, threatening the structural integrity of the cavity and its contents (e.g., stores, avionics, etc.). Below a critical length-to-depth ratio, the shear layer formed along the cavity mouth has enough energy to span across the opening. This shear layer impacts the downstream cavity corner and the generated acoustic disturbances propagate upstream, causing further instabilities near the cavity front. Consequently, a self-sustained feedback loop is established. This extreme flow environment calls for flow control ideas aiming to pacify the cavity by breaking the feedback loop and controlling the breakdown of the shear layer. This is the objective of the present work, which aims to assess changes of the cavity geometry and their effect on the resulting flow using detached-eddy simulation. For the cases computed in this work, quantitative and qualitative agreement with experimental data has been obtained. All of the devices tested achieved similar reductions in overall sound pressure level in the rear half of the cavity; however, a slanted aft wall provided the largest noise reduction in the front half of the cavity.