Author(s): Chunyang Hu; Yukai Zhang; Qiang Zhong; Yanchong Duan; Fujun Wang
Linked Author(s): Yanchong Duan
Keywords: Open channel flow; Direct numerical simulation; Free surface; Additional vortices
Abstract: In open-channel flows, there is a unique phenomenon of turbulent kinetic energy redistribution near the free surface region due to its suppression of vertical motion. As vortices are the primary cause of turbulent fluctuations, this energy redistribution suggests distinctive characteristics of vortices near the free surface compared to their counterparts in other wall-bounded turbulent flows. Recent studies have revealed the additional vortices phenomenon near the free surface, which is a significantly higher vortex density near the free surface region of open-channel flows than in corresponding regions of other wall turbulence (Duan et al., 2021). The underlying mechanism for this additional vortices remains unclear, and there are two potential hypotheses: (1) some specific surface mechanism enhances vortex generation near the free surface, or (2) some unknown surface effect reduces the dissipation rates of bed-originated vortices, leading to the vortices accumulation near the free surface.
Year: 2025