Direct numerical simulation of turbulent shear layer in an open cavity and its aero-optical effects

This study conducts direct numerical simulations (DNS) of the subsonic turbulent shear layer in an open cavity using a self-developed heterogeneous parallel solver to investigate its flow features and aero-optical effects. The DNS results show good agreement with the previous theoretical predictions and experimental data. Driven by Kelvin–Helmholtz instability, the shear layer rolls up into large-scale coherent vortices and induces primary and secondary recirculation zones within the cavity. Turbulence intensity is amplified along the shear layer and peaks near the trailing edge. Proper orthogonal decomposition reveals that the oscillatory energy of the shear layer is mainly concentrated in the low-order modes. Dynamic mode decomposition confirms that the unsteady dynamics follow the Rossiter mechanism, with the medium-to-large-scale coherent vortices being significantly enhanced in the mid-rear part of the cavity. Consequently, the wavefront distortion is more severe in the mid-rear cavity and exhibits a strong correlation with local density and pressure fluctuations. The oscillations of the shear layer and optical path difference (OPD) are dominated by the first Rossiter mode in the front and rear parts of the cavity but by the second Rossiter mode in the middle part. The energy of OPD oscillation contains negligible high-frequency components due to the spatial filtering effect of optical path integration, indicating that wavefront distortion is dominated by large-scale structures.