Experimental study on flow characteristics of open channels with submerged flexible vegetation

Laboratory experiments using LDV were performed to investigate the characteristics of water flow in open channels with submerged flexible vegetation.Test results reveal that the measured velocity distribution,which is S-shaped,can be divided into 3 areas: the internal area,the transition area and the upper area of vegetation.The flow velocity in the transition area is evidently affected by vegetation density,and the velocity gradient tends to increase with the vegetation density.It is also concluded that the turbulence intensity and Reynolds stress greatly increase in water flow with vegetation,and the two parameters increase with flow depth in the internal area and decrease with flow depth at the top layer of vegetation.The maximum values of these two parameters occur near the top of the vegetation,showing that copious energy exchange and powerful shear action exist in this area.