Evolution of vortical structures and turbulence in obstacle-influenced high-Reynolds-number cavity flows

High-Reynolds-number cavity flow with obstacles plays a critical role in many engineering applications; however, the underlying mechanisms governing vortex evolution and turbulence characteristics remain poorly understood. This study investigates the dynamic evolution of flow structures in a square cavity across Reynolds numbers ranging from Re = 1 × 105 to 7 × 105 using high-resolution particle image velocimetry. Results show that the primary vortex exhibits a multi-stage migration, moving from the wall toward the cavity center and stabilizing as Reynolds number increases, while the secondary vortex on the right side of the obstacle strengthens up to Re = 2.5 × 105 and diminishes at higher Reynolds numbers. At Re = 7 × 105, the primary vortex dominates the flow field, suppressing secondary vortices and concentrating over 68% of the total positive vorticity. Proper orthogonal decomposition reveals that energy becomes increasingly localized in low-order, large-scale structures, with the first 50 modes capturing approximately 59% of the total turbulent kinetic energy at Re = 2.5 × 105. Velocity analysis indicates a significant reduction in extremely high-speed regions with increasing Reynolds number, and the skewness coefficient in the primary vortex core exceeds 1, reflecting strong intermittent pulsations. These findings provide quantitative insight into the multi-scale interactions and self-organization of turbulence in high-Reynolds-number cavity flows with obstacles, offering guidance for flow control and mixing optimization in engineering applications.