滩地植被化复式河槽的水流阻力特性试验

Experiment of Flow Resistance in Compound Channel with Vegetated Floodplain

利用室内变坡水槽试验研究了复式河槽中滩地植被对水流阻力的影响,采用声学多普勒测速仪(ADV)观测了不同垂线、不同测点的垂线流速分布,分别讨论了水深、植被密度、淹没与非淹没植被对滩地阻力系数的影响。分析发现:滩地种有植被后,复式河槽的水流流速不再满足对数分布,在垂向可以认为是一个常数,且其值随植被密度的增加而减小;阻力系数在滩地无植被时受水深的影响很小,在有植被的工况中,阻力系数会随水深的增加而显著增大,其值与植被密度满足线性关系;滩地植被淹没后,虽然滩地阻力系数也随水深的增加而增大,但其增幅较非淹没植被工况中要小。

The influences of floodplain vegetation to the flow resistance are experimentally studied.The experimental data of local flow velocities at different vertical measurement lines are obtained by the Micro-ADV.The effects of flow height,vegetation density,submerged or emerged vegetation to the resistance coefficient are discussed.When the vegetation is planted on the floodplain,the vertical velocity is not following the logarithmic distribution and the value which is affected heavily by the vegetation density can be regarded as a constant in the vertical direction.The roughness coefficient changes slightly with the flow height in the case without vegetation while its value increases significantly with the increasing depth of water and vegetation density in the vegetated ones.Though the resistance coefficient rises with the climbing water level when the vegetation is submerged on floodplain,its value is relatively small,comparing with the emerged case.