Linear Aeroacoustics of Deep Cavities

This study examines the linear aeroacoustic behavior of an academic device that comprises deep cavities surrounding a cylindrical duct. Without flow, the study reveals the emergence of transmission peaks within the expected stop-band. The transmission peaks are due to interactions between the cavities. Notably, different geometrical configurations exhibit different peaks, while the effective impedance of the cavities remains the same. This highlights the limitations of the impedance concept even in the absence of flow. In presence of flow, the study shows a localized frequency gain zone with a constant Strouhal number. The results also indicate that the impedance differs between the two propagation directions. Additionally, the scattering matrix analysis reveals that the peaks are most amplified by the flow when propagating in the opposite direction.