Experimental and Numerical Investigation of a Cavity with Passive Control Devices Under Transonic Flow

Abstract Rectangular cavities in embedded weapons bays generate intense unsteady flow phenomena under high-speed conditions, leading to significant aerodynamic noise and structural concerns. This study investigates the flow and acoustic characteristics of such cavities using both wind tunnel experiments and delayed detached eddy simulation (DDES) at transonic speeds. Dynamic pressure measurements were conducted for cavities with different length-to-depth ( L / D ) ratios and trailing-edge geometries across Mach numbers ranging from 0.6 to 1.2. The experimental results reveal that modifying the trailing edge from a baseline geometry to a slanted or stepped configuration significantly alters the flow structure and reduces acoustic loading. At Mach 0.9 and 1.05, the overall sound pressure level at the downstream end of the cavity ( X / L = 0.958) is reduced by more than 10 dB, with the step configuration achieving the highest attenuation. Numerical results using DDES agree well with experimental data and further illustrate the suppression of vortex structures and mode switching, from second-mode (St ≈ 0.7) to first-mode (St ≈ 0.3) oscillations. These findings demonstrate that passive control via geometric modification of the trailing edge is an effective strategy for mitigating cavity-induced noise in transonic flows.