基于格子Boltzmann的植被对河道的流场和污染物输运的影响研究

Effects of Vegetation on the Flow Field and Pollutant Transport of River Channel Based on Lattice Boltzmann

为了研究植被分布对河道输水能力及对污染物输运能力的影响机制,基于格子Boltzmann数值模拟方法,将植被的阻碍作用概化为植被粗糙率,采用D2Q16多速度浅水模型模拟计算植被区间隔分布的河道中的流场,再将计算得到的流场信息与D2Q5对流扩散模型得到的污染物浓度场耦合,研究植被对流场以及污染物输运的影响。结果表明:河道纵断面植被区流速降幅、过渡区和中心区流速增幅均与植被密度呈线性正相关,横断面中心区流速远大于过渡区和植被区,植被区和中心区流速呈直线分布,且过渡区流速与植被密度呈二次幂相关,污染物浓度的衰减幅度与植被区间隔距离呈正相关性。植被能够改变污染物输运的轨迹,且能有效减少河道下游污染物的浓度。该研究可为城市人工生态景观建设中河道内人工布置植被的适宜密度和间隔提供参考。

Analyzing the impacts of vegetation distribution on the water transport capacity of rivers and the transport capacity of solutes such as pollutants is of great significance for reducing pollutants in downstream rivers and protecting the ecological environment of rivers.Based on the lattice Boltzmann numerical simulation method,the obstruction effect of vegetation is generalized as vegetation roughness,and the D2Q16 multi-velocity shallow water model is used to simulate and calculate the flow field in the river channel with spaced vegetation zones.The calculated flow field information is then combined with the D2Q5 convection-diffusion The pollutant concentration field obtained by the model is coupled to study the influence of vegetation on the flow field and pollutant transport.The results are as follows.The flow velocity decrease in the vegetation area of the river longitudinal section and the flow velocity increase in the transition area and central area are linearly positively correlated with the vegetation density.The flow velocity in the central area of the cross section is much greater than the transition area and vegetation area.The flow velocity in the vegetation area and the central area are linearly distributed.Moreover,the flow velocity in the transition zone has a quadratic power correlation with the vegetation density,and the attenuation amplitude of the pollutant concentration has a positive correlation with the distance between vegetation zones.Vegetation can change the trajectory of pollutant transport and can effectively reduce the concentration of pollutants downstream of the river.This study can provide a reference for the appropriate density and spacing of artificially arranged vegetation in river channels in the construction of urban artificial ecological landscapes.