An Experimental Study of the Flow Structures in Vegetated Open Channels

To investigate the effects of vegetation on flow Reynolds stress and turbulence intensity,an experiment was performed with plastic rods and artificial waterweeds in a slope-variable laboratory flume; an acoustic Doppler velocimeter was used to measure the instantaneous velocity at different points on the vertical line under different conditions; Turbulence parameters at each measuring point were calculated, such as Reynolds stress and turbulence intensity; The effects of vegetation on flow structures were analyzed through comparison with the turbulence characteristics of uniform open channel flows without vegetation distribution. The experimental results show that the turbulent constant Reynolds stress layer exists in water flows with vegetation distribution compared with the water flows without vegetation distribution. Without vegetation distribution, the viscous shear stress at the flume bed mainly affects the area between the bed and the level at a depth about 30% of the water depth. With vegetation distribution, the effect of the viscous shear stress at the bed weakens.The highest flow turbulence intensity with vegetation distribution occurs within the range of vegetation height.