Effect Of Rigid And Flexible Vegetation On Flow Characteristic

Vegetation population plays a vital role in river ecosystem, It not only can provide habitat for aquatic organisms and microorganisms, but also can purify water and one important factor of keeping river ecological diversity. In this research, with uniform round stalks and flexible plastic feather as experimental material to simulate rigid unsubmerged vegetation and submerged vegetation respectively. Under 70L/s 80L/s,-90L/s three discharge, and 54 plants/m2,108 plants/m2,202plants/m2 three vegetation density, using acoustics doppler current meter (ADV) and ABF2-2 topography measurement system to measure the flow velocity of 9 cross section and three profile and the the water depth of 5 along profile, respectively.The effect of rigid-flexible vegetation population, flexible-rigid vegetation population and flexible vegetation population on velocity distribution and relative turbulence intensity are analyzed. The results are as follow.For the water depth, due to the resistance of the role of vegetation, the water depth increased gradually before the vegetation area and reache the highest point at 5m section, after flow entering the vegetation area, with the resistance of vegetation decrease, water depth gradually declined and reaches a minimum value points at 9m section. Through the analysis of experimental data shows that in the range of discharge and vegetation density in this experment, the effect of flexible on flow more than rigid vegetation.For velocity distribution, due to the impact of resistance from side wall, the longitudinal velocity and vertical direction of longitudinal section 1 is lower than other two, under this discharge and vegetation density condition, the effect of vegetation density on longitudinal velocity distribution is greater than discharge. Relative turbulence intensity before entering the vegetation area is gentle, as the water entering the vegetation area relative turbulence intensity began change. The relative turbulence intensity in flexible vegetation section is significantly greater than the rigid section and without vegetation section. For three directions, the relative turbulence intensity for longitudinal direction>transverse direction>vertical direction, whether there is vegetated area or not.The results of this article will elaborate the relationship between the rigid-flexible simulate vegetation and river flow characteristics which can provid some theoretical basis for natural river training, and repairing.