We present numerical investigations of flow-acoustic resonances in deep and inclined cavities using wall-resolved large-eddy simulations. The cavity geometry has a fixed aspect ratio of $D/L=2.632$, subjected to two Mach numbers of 0.2 and 0.3 at three different angles of inclination ($\alpha ={30}^{\circ }, {60}^{\circ }$, and ${90}^{\circ }$). Fully turbulent boundary layers generated from independent precursor simulations are employed upstream of the cavities. The simulation results show significant differences in aeroacoustic response between inclined and orthogonal cavities, particularly at $M_{\infty }=0.3$, where the inclined cavities exhibit stronger resonances (by more than a 20 dB) at a lower peak frequency ($\mathrm{St}=0.276$) than the orthogonal cavity, whose peak occurs at $\mathrm{St}=0.849$. Acoustic modal analysis identifies these frequencies as the first and second eigenmodes, respectively. Further analysis shows that the difference in mode selection is linked to the hydrodynamic modes that couple with the acoustic modes. In the orthogonal cavity, the second hydrodynamic mode prevails, in which two relatively small vortices travel across the cavity opening simultaneously. In the inclined cavities, however, a single large-scale rollup vortex corresponding to the first hydrodynamic mode is generated owing to strong Kelvin-Helmholtz instability in the shear layer. More importantly, this vortex spends much of its lifetime growing in size rather than traveling rapidly downstream, resulting in a longer crossing time per cycle that correlates with the first acoustic eigenmode frequency ($\mathrm{St}=0.276$). In addition, aeroacoustic resolvent analysis indicates that inclined cavities amplify acoustic responses more effectively and exhibit weaker source-sink cancellation than the orthogonal cavity. These mechanisms are identified as the primary contributors to the enhanced aeroacoustic response of the inclined cavities. Finally, it is proposed that the ratio of acoustic particle displacement to momentum thickness can be used as a criterion for predicting the onset of deep cavity resonance associated with the distinctive vortex dynamics identified in this paper.

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• Aeroacoustics
• Vortex dynamics
• Large eddy simulations