现代城区热环境与污染物扩散的大涡模拟研究  

Study on thermal environment and pollutant dispersion in real urban area by Large Eddy Simulation

作　　者：李海锋[1] 王博斌[1] 崔桂香[1] 张兆顺[1] 

机构地区：[1]清华大学航天航空学院,北京100084

出　　处：《中国科学：物理学、力学、天文学》2015年第10期61-77,共17页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(批准号:11132005;11490551)资助项目

摘　　要：本文以北京(CBD)中心商业区为例,模拟了典型夏季晴天CBD小区大气流动,考察了CBD小区风场、温度场和污染物扩散过程.数值求解过滤的不可压缩流体Navier-Stocks方程组,采用有限体积的离散方法,时间方向推进采用三阶Runge-Kutta法,按照SIMPLE算法求解不可压缩大涡模拟方程组.为适应城市小区内复杂的湍流流动,采用Lagrange动力模式封闭亚格子雷诺应力.通过表面能量平衡关系确定建筑表面的温度分布.结果表明壁面温度主要由太阳辐射决定,而空气温度主要由对流换热决定.通过研究风向和浮力对污染物浓度分布的影响,发现污染源近场的扩散过程受建筑分布、风向和局部流场的影响显著,冠层内羽流偏转明显;浮力促进垂向对流,扩大垂向羽流宽度,但对展向羽流宽度影响不大.Modern urban districts are mainly composed of buildings and roads. The buildings are usually tall and various in shapes and moisture flux on the surfaces is of low level. Atmospheric Environment in modern urban districts gets wide attention because of those landmark buildings and the large population in it. In this paper, the central business district（CBD） is set as an example to study thermal environment and pollutant dispersion in urban area. Atmospheric flows in typical summer sunny days are simulated by Large Eddy Simulation（LES） and wind field, temperature field and dispersion process of point pollutant are analysed. The momentum, mass and thermal transport equations are discretized by the finite volume method with non-staggered grids and a third-order Runge-Kutta intergration in time. The filtered Navier-Stocks equations are solved using SIMPLE algorithm. Lagrangiam dynamic model, which is suitable for complex turbulence in urban districts, is applied to close sub-grid stress. Temperature distribution is calculated according to surface energy balance relation. The results reveal that temperature on the wall surfaces is mainly determined by solar radiation while that in air is mainly determined by convection. Near field distribution of pollutant is considerably influenced by wind direction, building distribution and partial flow field. Meanwhile bouyancy enhances vertical convection and expands vertical plume width, while has no considerable influence on spanwise plume width.

关 键 词：现代城区 大涡模拟 点污染源 

分 类 号：X16[环境科学与工程—环境科学]