Near-wall effect on vortex dynamics in the flow around a rectangular cylinder

作者：Jiang-Hua Li, Bo-Fu Wang, Xiang Qiu, Quan Zhou, Shixiao Fu, Yulu Liu · 发表于：Journal of Fluid Mechanics · 年份：2025 · DOI：10.1017/jfm.2025.365 · 被引用次数：12 · 研究领域：Fluid Dynamics and Vibration Analysis、Fluid Dynamics and Turbulent Flows、Wind and Air Flow Studies

This study presents a novel investigation into the vortex dynamics of flow around a near-wall rectangular cylinder based on direct numerical simulation at $Re=1000$ , marking the first in-depth exploration of these phenomena. By varying aspect ratios ( $L/D = 5$ , $10$ , $15$ ) and gap ratios ( $G/D = 0.1$ , $0.3$ , $0.9$ ), the study reveals the vortex dynamics influenced by the near-wall effect, considering the incoming laminar boundary layer flow. Both $L/D$ and $G/D$ significantly influence vortex dynamics, leading to behaviours not observed in previous bluff body flows. As $G/D$ increases, the streamwise scale of the upper leading edge (ULE) recirculation grows, delaying flow reattachment. At smaller $G/D$ , lower leading edge (LLE) recirculation is suppressed, with upper Kelvin–Helmholtz vortices merging to form the ULE vortex, followed by instability, differing from conventional flow dynamics. Larger $G/D$ promotes the formation of an LLE shear layer. An intriguing finding at $L/D = 5$ and $G/D = 0.1$ is the backward flow of fluid from the downstream region to the upper side of the cylinder. At $G/D = 0.3$ , double-trailing-edge vortices emerge for larger $L/D$ , with two distinct flow behaviours associated with two interactions between gap flow and wall recirculation. These interactions lead to different multiple flow separations. For $G/D = 0.9$ , the secondary vortex (SV) from the plate wall induces the formation of a tertiary vortex from the lower side of the cylin...