Research On 3D Flow Model Considering Vegetation Effects

River ecology has received more and more attention in recent years.The existence of vegetation is an important factor in river management,vegetation will affect the river's capacity of water flow and sand-carrying,so it has important research value in ecological bank revetment and dike revetment.Based on the existing water flow model COASTALTOOL,this paper summarized the research progress of vegetation effects on water flow so far,corresponding improvements were made to the model to enable it to calculate the role of vegetation,then conducted a preliminary study on the effect of vegetation and water flow through combination with physical experiments.Firstly,based on the existing research on Li Shaowu's self-developed and continuously developed quasi-three-dimensional tidal wave motion model,the role of vegetation was considered.Vegetation term was added to the governing equation of the model while the drag force coefficient was optimized reasonably.The drag force coefficient is improved by referring to the shielding effect of pile group around the current.At the same time,the concept of vegetation density proposed by predecessors was introduced,and its applicability under submerged and non-submerged conditions was different,so has to choose the certain value under different condition.The improved model is solved and then validated by the experimental data of predecessors.It has a good simulation effect on the water flow movement of vegetation submerged and asymmetrically distributed along the channel section,which can reflect the different flow velocity distribution rules in vegetated and non-vegetated areas in the vertical,and the kinetic energy of the turbulence is maximized at the top of the vegetation;In the horizontal direction,it can also simulate the uneven distribution of vegetation,and the results show that a redistribution process exists in the cross section under the influence of vegetation.A flume was used to study the effect of vegetation under complex flow conditions,and it was shown that the density of vegetation was the main factor affecting the resistance,while the arrangement of vegetation had little influence,and more abundant flow field data were obtained by using the model.