含植物明渠水流运动特性试验研究

Experimental study on the characteristics of flow movement in open channel with vegetation

水生植物广泛存在于天然河流的岸滩和浅水区域,对河道水流运动产生一定影响。该文利用声学多普勒测速仪(ADV)开展了不同类型植物对明渠水流运动特性影响的实验研究。结果表明:在淹没植物上方及挺水植物杆两区域内,植物对水流运动影响较小,其流速分布满足典型对数分布形式;水流自明渠上游过渡到植物区首部时,因水流阻力突然增大而发生剧烈紊动,当植物相对体积较大时,植物区首部的二次流运动方向较上游区发生反转,并在下游区形成明显旋涡流;在植物区大体积植物的阻隔作用使明渠动量横向波动幅度明显加大,在下游区强度较大的旋涡流明显减弱了水流动量的整体单向输运强度。

Aquatic vegetation widely exists in the shore and shallow water areas of natural rivers, which have a certain impact on river flow movement. In this paper, the effects of different types of vegetation on the flow characteristics of the open channel are studied by using acoustic Doppler velocimeter(ADV). The results show that the flow movement is little affected in the zone above the submerged vegetation and in the stem zone of the emergent vegetation, and the velocity distribution satisfies the typical logarithmic distribution. When the flow transitions from the upstream to the head of the vegetated region, the turbulence occurs due to the sudden increase of the flow resistance. If the relative volume of the plant is relatively large, the direction of the secondary flow in the head of the vegetated region is reversed from that in the upstream region. And a distinct vortex flow is formed in the downstream. The transverse fluctuation of momentum in open channel is obviously increased by the blocking effect of large-scale vegetation in the vegetation area, and the overall one-way transport intensity of water flow is obviously weakened by the strong eddy current in the downstream area.