植被作用下明渠交汇水流特性数值模拟研究

Numerical Simulation of Flow Characteristics in Vegetated Open-channel Confluences

水流交汇现象普遍存在于天然河网系统和水利工程中,其水流特性研究对河道治理、美化城市水环境等具有重要意义。利用Mike21FM模型对明渠交汇水流进行数值模拟,并采用水槽试验对该模型进行了验证,最后分析了明渠直角交汇水流在不同汇流比情况下及植被影响下的水流特性。结果表明,汇流比越大,交汇口上游水位越高,下游水位波动越大,主渠高流速区偏向交汇口对侧,低流速区位置到交汇口上游角的距离有所增加,同时分离区中心的流速减小。植被的存在使交汇口上游和下游水位均有抬升,且对分离区内的水位影响较大,同时,支渠流速偏转起始位置距交汇口距离较无植被时有所增加。

Channel confluences are common in natural rivers and hydraulic engineering.It is of great significance to study the flow characteristics in open channel junctions for river regulation and urban water environment beautification.Thus numerical simulation based on Mike21 and validated by flume experiment is carried out to model open-channel confluence.And then,the flow characteristic variation under the condition of different discharge ratios and vegetation influence in a right-angled open-channel junction are systematically analyzed.The results show both the water level of main river upstream and the fluctuation of downstream increase with the increase in the discharge ratio and it brings a deviation of the high velocity zone and increase in distance from low velocity zone to conjunction angle,and the velocity at the center of the separation zone decreases.To a confluence flow with vegetation,the water level of the upstream and downstream increases,and it has a greater impact on the water level in the separation zone.Meanwhile,the distance from the starting position of the branch channel velocity deflection to conjunction angle increases.The research results can be a reference for the development of irrigation and drainage engineering,urban environmental hydraulic engineering and ecological revetment.