沉水植被群落状态对水流阻力的影响

沉水植被在水流作用下状态会发生改变,进而会对河流生态系统产生一定影响。通过室内水槽模型实验观测了均匀流下沉水植被群落内部各植株的状态,并分析了沉水植被群落状态以及内部植株相对间距对植被群落水流阻力的影响。研究结果表明:在沉水植被群落内部,各个植株的相对刚度各不相同,并且其状态随来流条件变化而改变,对于不同种群的沉水植被群落,在相同水流条件下也可能呈现出不同的状态,当沉水植被群落的植被处于非直立状态时,随着植被从弯曲状态向直立状态转换,水流阻力也在不断增大;植被处于完全刚性状态时,阻力系数则与植被相对刚度无关,仅与水流条件有关,随着流速的增大而减小;沉水植被群落内部植被相对间距不同,其阻水效果也不同,在相同植被状态下,植被相对间距越大,也就是植被带越长,植被阻力越大。

Influence of submerged vegetation communities on flow resistance

The state of the submerged vegetation changes along with the flow conditions, which will have a certain impact on the river ecosystem. Based on the indoor flume experiment, the state of various submerged plants in uniform flow is observed. The influences of the states of submerged vegetation communities and the relative distances of the submerged vegetation within the communities on the flow resistance are analyzed. The results show that the relative rigidity of various submerged plant are different and vary along with the flow conditions. For different submerged vegetation communities, the state may also be difference under the same flow conditions. In the bending-to-erecting process of submerged plant, the flow resistance increases. When submerged vegetation becomes completely rigid, the resistance coefficient has no relation with relative rigidity but decreases with flow velocity. The flow resistance changes with the relative distance of the submerged plant, that the wider the relative distance of the submerged plant is, the greater the flow resistance is.