Flow characteristics in open channels with aquatic rigid vegetation

Abstract

In order to study the flow characteristics in water bodies with rigid aquatic vegetation, series of laboratory experiments are carried out in an open channel, in which glass rods are used as plants with diameters of 6mm, 8mm and 10mm, respectively. For each diameter of glass rods, four typical cases are considered with various densities and arrangements of glass rods. The flow velocities in the four cases are measured by the 3-D laser Doppler velocimeter (LDV). The water surface slope, the flow velocity, the water head loss, the vegetation drag force and the hydraulic slope are calculated, analyzed and discussed. The horizontal, vertical and total vegetation densities in the vegetation area are defined and the relationship between these physical parameters and the water surface slope are studied. The head loss and the hydraulic slope in the vegetation area are also calculated, compared and analyzed. It is indicated that the water surface slope and velocity, the head loss and the hydraulic slope in the vegetation area have a close relationship with the arrangement, the density, and the plant diameter of the vegetation.