Study Of Flow Structure And Mixing-transporting Characteristics Of Open Channel Flow Influenced By Rigid Vegetation

Aquatic vegetation is significant in river ecology.Vegetation in rivers provides important dissolved oxygen for containing the self-purification ability of the river.Meantime,it also provides essential habitats for different kinds of aquatic biology and also the places for fish spawning.However,the vegetation also causes extra resistance to the flow,which in some way decreases the bulk velocity and influences the discharge capacity of the channel.Thus,how to achieve a balance between preventing the flood and protecting the environment has interested a lot of scientists.Thus,this article will focus on the flow structure and mixing-transporting process in open channels influenced by the rigid vegetation(a common kind),which focuses on the bulk average velocity when the channel is fully covered by the submerged vegetation,the velocity distribution when channel is partly covered by the submerged vegetation,the longitudinal dispersion coefficient when the channel is partly covered by the emergent vegetation and the influence of the vegetation on the transverse mixing.In order to estimate the bulk average velocity when the channel is fully covered by the submerged vegetation,we start from the Kolmogórov turbulence theory to find the scale relationship between the dominant eddies to obtain a Darcy–Weisbach-like formula.After that,we use Genetic program to analyze the datasets and obtain a practical way to estimate the bulk average velocity.For the velocity distribution when the channel is partly covered by the submerged vegetation,we conduct a series of experiments to discover this kind of unique velocity profile,including the transverse distribution of the depth-averaged velocity and the detailed 2D distribution of the local velocity.When it comes to the longitudinal dispersion coefficient when the channel is partly covered by the emergent vegetation,we build a simplified model adapted from Chickwendu's N zone model for it.And regards to the influence of vegetation on the transverse mixing process,we start with the mixing processes without vegetation,and then compare it with the transverse turbulent diffusion influenced by vegetation discovered by previous research.