沉水植物对城市河道糙率的影响

Influence of Submerged Plants on Roughness in Urban Rivers

在城市河道等明渠中,沉水植物可对水体起到净化作用,但沉水植物过于密集或草高过大也会带来提高河底糙率等负面作用。为研究不同密度(丰度)和高度沉水植物对河底糙率的影响,利用真实水草(菹草)进行水槽试验,采用正交组合方案,拟定不同草高、丰度菹草和水位工况,测量断面流速分布,获得不同水位下不同丰度、高度沉水植物对水流的阻碍作用及对河道糙率的影响。结果表明,草高组多数测线流速分布均为"S"型分布;丰度组各测线流速关系均为中>左>右;菹草明显提高河底糙率,且菹草高度与水位的比值对槽底糙率的影响程度随断面平均流速增加而减弱,随菹草丰度的增加而减弱。

In open channels such as urban river channels,submerged plants play a role in the purification of water bodies,but if the abundance of submerged plants is too high,there will be some negative effects such as increasing the river bottom roughness.In order to study the impact of submerged plants with different density(abundance)and height on river bottom roughness,the real grass(Potamogeton crispus)was used to carried out flume test.Using orthogonal combinations,the flow velocity distribution of the cross section under different abundance aquatic plants and hydraulic conditions was simulate to obtain the impact of different abundance submerged plants on water flow obstruction and river roughness.The results show that most vertical velocity of profiles in different grass heights appeared S-shaped curve;All of the relationships across vertical velocity of profiles in different abundances is,medium>left>right;Potamogeton crispus significantly increased the river roughness,and the impact of grass height on the river roughness decreased with the increase of the average flow velocity of the section as well as the abundance of Potamogeton crispus.