Spanwise confinement effects on a stably stratified shear layer

抄録

Direct numerical simulations (DNS) are conducted to investigate the effects of spanwise domain size on stably stratified turbulent shear layers. The focus is on the formation and spatial organization of elongated large-scale structures (ELSS), which emerge following the transition from Kelvin–Helmholtz instability and characterized by streamwise extents far exceeding the shear layer’s thickness. Simulations are conducted for a temporally developing shear layer under stable density stratification. The spanwise extent is varied, while the streamwise and vertical domain sizes are fixed. Flow visualizations, one-point statistics, energy spectra, and two-point correlation functions are used to assess the influence of spanwise confinement on the transition process and late-time turbulence characteristics. The results show that when the spanwise domain size is very small, the transition process is altered and ELSS fail to develop properly. For intermediate domain sizes, the streamwise elongation of ELSS is captured, but their meandering and spatial repetition are suppressed. Statistical analysis reveals that while the meandering of ELSS contributes to large-scale structure, the presence of multiple alternating ELSS in the spanwise direction is more critical to the overall flow statistics. These findings emphasize the importance of spanwise configurations of ELSS in the dynamics and energetics of stably stratified shear layers.