Different roles of submerged aquatic vegetations in open-channel flow and wind-induced flow

Submerged aquatic vegetation (SAV) fundamentally alters hydrodynamic processes in aquatic systems, yet its differential roles in open-channel flow (OCF) vs wind-induced flow (WIF) remain poorly quantified. This laboratory study uses physically similar recirculating flume, wind-flow flume, and two-dimensional particle image velocimetry measurements to contrast turbulence modulation mechanisms. SAV reduces 26% and 31% of velocity within canopy for WIF and OCF, respectively, while increasing velocities above canopy. Critical divergences emerge in turbulence regulation: OCF transforms from bed-shear-dominated “J-shaped” to canopy-top-shear-dominated “inverted S-shaped” profiles, where Kelvin–Helmholtz vortices maximize Reynolds stress and anisotropy at canopy interfaces. In contrast, WIF maintains surface-anchored turbulence, where SAV suppresses up to 67% of turbulent intensity within canopy, accelerates turbulence decay along depth, and promotes isotropy. Quadrant analysis confirms sweeping dominance (RS4) in OCF canopies vs homogenized momentum contributions in WIF. Turbulent kinetic energy budgets reveal shear production and wake production drive OCF turbulence at canopy tops, while SAV depresses canopy production more severely than dissipation in WIF. Overall, SAV acts as a “turbulence amplifier,” promoting turbulent energy development by substantially enhancing turbulent intensity and anisotropy within the canopy. In contrast, SAV functions as a “turbulence suppressor” in WIF, inhibiting turbulent development by reducing turbulent intensity and diminishing turbulence anisotropy inside the canopy.