Cavity flows at high Reynolds numbers

This study investigates lid-driven cavity flows at high Reynolds numbers (Re = 1 × 105–1 × 106) using particle image velocimetry. The results reveal significant changes in vortex dynamics, including the expansion and increased intensity of the primary vortex, suppression of secondary vortex regions, and thinning of the boundary layer. As the Reynolds number increases, the impact of cavity walls becomes more pronounced, leading to smaller vortices near the walls and enhanced energy dissipation, accompanied by a gradual decrease in flow velocity. A proper orthogonal decomposition analysis of the fluctuating velocity field reveals that the low-order modes dominate flows at all Reynolds numbers, with the cumulative energy contribution of the first four modes accounting for 49.70% at a Reynolds number of 1 × 105. As the Reynolds number increases, the energy begins to disperse into high-order modes. When the Reynolds number reaches 7 × 105, the energy contribution of the first four modes drops to 27.93%, reflecting the generation and evolution of local vortices and small-scale features. Low-order modes effectively capture the main flow characteristics, but at high Reynolds numbers, higher-order modes are required to fully represent the complex turbulent state.