不同角度丁坝对污染物迁移扩散的影响  

Impacts of spur dikes with different angles on the diffusion and migration of pollutants

作　　者：童艳[1] 陈丽萍[1] 

机构地区：[1]南京工业大学城市建设与安全工程学院,南京210009

出　　处：《安全与环境学报》2013年第6期274-278,共5页Journal of Safety and Environment

基　　金：国家自然科学基金项目(51109106);2011年度省属高校自然科学基金项目(11KJB570001)

摘　　要：流动的分离和不同尺寸涡的形成,使得丁坝周围的湍流非常复杂。为分析其流场对污染物迁移扩散过程的影响,建立了三维瞬态自由水面流动的VOF压缩性模型,在此基础上建立污染物水体迁移扩散方程。对置于试验水槽中的非淹没60°、90°和120°丁坝进行了试验和模拟。模拟中用二阶精度的Gamma格式离散对流项,结果与试验结果吻合得较好。结果表明,90°丁坝形成的涡最长而120°丁坝形成的涡最短。由于横断面收缩得最多,90°丁坝主流速度最大。当污染物在丁坝上游泄漏时,污染物质量浓度随时间而下降。主流区内质量浓度迅速达到峰值,迅速衰减;而回流区质量浓度缓慢达到峰值,缓慢衰减。丁坝岸边的污染物质量浓度完全由回流决定,质量浓度增加与下降的速度随回流速度增加而增加。靠近丁坝的横截面上,主流与回流之间点的质量浓度随丁坝角度增加而下降。质量浓度波动与丁坝角度有关。远离丁坝的横截面上,主流与回流之间点的最大质量浓度随丁坝角度增加而下降。The present paper aims to introduce our study on the im pacts of spur dikes in different angles on the diffusion and migration of the pollutants. As is known, turbulent flow around a spur dike is ex tremely complex by nature because its separation and vortices tend to result in different sizes. In order to analyze the impacts of the flow fields on the pollutant diffusion and migration, we have developed a transient 3D model based on a compressible VOF （volume of fluid） method in hoping to simulate the migration of dissolved pollutants in the dike. VOF is by nature a numerical means for acquiring and tracking the free surface of the water flow. It is on the basis of using the numerical simulations we have performed experiments on a non submerged spur dike in a laboratory flume with 60°, 90° and 120°an gle respectively. And, then, we have adopted a secondorderaccu rate Gamma differencing scheme to discrete the convection terms. The simulation results of ours proves to be in a perfect consistence with those of experiments. The vortex induced by the 90~ spur dike is the longest, whereas the vortex by the 120~ spur dike is the shortest. The velocity in the main flow of the 90~ spur dike is the highest due to its maximum crosssection reduction. When pollutants are released into the flow at the upstream, the concentration of the pollutants proves to decrease with time. On the other hand, the concentration in the main flow zone tends to reach its maximum then drops quickly, but it does slowly in the back flow zone. However, the concentration of pollu tants on the riverside of the spur dike can be controlled totally by the back flow. What is more, the increasing or decreasing speed of the concentration has been found increasing with the increase of the speed of the backflow. At the crosssection near the spur dike, the pollutant concentration at the points between the main flow and the backflow tends to decrease with the increase of the spur dike angle. Thus, it can be concluded that the variation of the concen

关 键 词：水力学及河流动力学 丁坝 污染 迁移扩散 模拟 试验 

分 类 号：X522[环境科学与工程—环境工程]