变扩散系数倾斜岸三维浓度分布及混合区计算  

Calculation methods for 3D concentration distribution and pollutant mixing zones using non-uniform diffusion coefficients

作　　者：武周虎[1] WU Wen 黄真理[3] 

机构地区：[1]青岛理工大学环境与市政工程学院,山东青岛266033 [2]Queen's University,Kingston [3]中国水利水电科学研究院水电可持续发展研究中心,北京100038

出　　处：《水力发电学报》2017年第4期38-47,共10页Journal of Hydroelectric Engineering

基　　金：国家自然科学基金(51379097;51379218)

摘　　要：在环境水力学迁移扩散方程的求解和环境水质模型中,通常将扩散系数按常数来处理。但研究发现在长江三峡建水库前黄沙溪市政排污口的污染混合区形状,并不符合常数扩散系数条件下的污染混合区外边界标准曲线(曲面)方程和几何特征参数关系。在倾斜岸河库的岸边等强度点源条件下,求解了变扩散系数简化三维移流扩散方程的浓度分布,进行了浓度分布的特性分析。在此基础上,推导出了污染混合区最大长度、最大宽度与最大深度和相应纵向坐标、水面面积及水下体积的理论公式,给出了污染混合区外边界标准曲线(曲面)方程,分析了扩散系数的变化对污染混合区形态的影响规律,提出了确定变扩散系数的双断面法和等浓度线法以及最大允许污染物负荷的计算方法,给出了按常数扩散系数处理的适用条件。实例分析表明,变扩散系数条件下的污染混合区外边界标准曲线方程和几何特征参数关系,能够较好地表征黄沙溪和涪陵磷肥厂排污口的污染混合区形状。Diffusion coefficients are usually taken as constants in solving the advection-diffusion equations and water quality models of environmental hydraulics. However, sometimes this is a poor simplification, such as in the case of pollutant mixing zones around the municipal sewer outfall in the city of Huangshaxi before the construction of the Three Gorges reservoir. We observed that the shapes of these mixing zones were much different from those that were predicted, under the assumption of constant diffusion coefficients, by using the standard curve equation （for the curved surface） of their outer boundaries or the relationship of their geometric characteristic parameters. In this study, focusing on the cases of point sources of equal intensity located at the sloped banks of rivers or reservoirs, we have solved a simplified three-dimensional advection-diffusion equation of pollutant concentration using non-uniform diffusion coefficients and analyzed the characteristics of concentration distribution. We also derived theoretical formulae of maximum length, maximum width, and maximum depth and their corresponding locations in the mixing zone as well as its surface area and underwater volume. In addition, this paper gives a standard curve equation for the outer boundaries of mixing zones and an analysis of the effects of spatial variation in diffusion coefficients on the shape of mixing zones, including the limitation of constant diffusion coefficient models, and develops a double cross-section method and isoeratic line method to determine non-uniform diffusion coefficients and a calculation method for the maximum allowablepollutant load. Applications show that the non-uniform diffusion coefficient model and its calculations can better characterize the pollutant mixing zones around the sewer outfalls in Huangshaxi and the Fuling phosphate fertilizer plant.

关 键 词：环境水力学 变扩散系数 三维浓度分布 污染混合区 几何特征参数 双断面法 等浓度线法 

分 类 号：X143[环境科学与工程—环境科学] X52