Turbulence Affected by Submerged Auqatic Vegetation under Wind- induced Flow

Abstract

Submerged aquatic vegetation (SAV) changes the turbulent structure of rivers, wetlands, estuaries, and lakes. However, few studies have focused on the influence of SAV on hydrodynamic characteristics under wind-induced flow. Therefore, laboratory experiments were conducted to study the effects of SAV on the flow structure and turbulence characteristics under wind-induced flow and spectral based decomposition method were used to separate turbulence and wave velocity. Result shows that SAV reduced local velocity within canopy and elevates the location of the zero-velocity point. The canopy drag caused by SAV increase the decay rate of turbulent Reynolds stress along depth while hardly influence wave Reynolds stress. Canopy drag depress the turbulent RMS velocity and wave orbital velocity, the suppression of turbulence by SAV is greater compared to the impact on wind-wave. The presence of SAV leads to the decrease in TKE production and dissipation rate within canopy. The canopy drag more effectively diminishes TKE production than it does the dissipation. Research on local isotropy of SAV in wind-induced flows shows that the presence of SAV promotes a gradual transition from local anisotropy to local isotropy in turbulence within canopy. And quadrant analysis reveals that the presence of SAV reduced the probabilities and the contribution to turbulent momentum of ejection and sweep.