Experimental study of flexible and rigid vegetation in an open channel

In this paper, the effect of a rigid and flexible submerged vegetation, with a characteristic low density, on a transversal current was analyzed. Different configurations as vegetation type, flow depth and velocity were investigated in the laboratory flume. 3D velocity components and turbulence characteristics, such as turbulence intensity and Reynolds stresses, were conducted at different measurement points by the Acoustic Doppler Velocimeter (ADV) system. The velocity and turbulence profiles and distributions were plotted in horizontal and transversal sections, in order to quantify the effect of the two kinds of vegetation on the crossflow. The results showed a local behavior, due to the particular low vegetation density that do not allow to consider the flow field homogeneous at the stem scale. Besides, flow velocity deceleration and turbulence increase were stronger under the top of the rigid vegetated layer than in the case of flexible stems.