Parallel computation of atmospheric pollutant dispersion under unstably stratified atmosphere

Pollutant dispersion under unstably stratified atmosphere was investigated numerically using the finite element method. The effects of atmospheric stability on plume trajectory were studied using a three-dimensional second-order closure dispersion model. The numerical model was implemented using domain decomposition method and carried out using a parallel computer. The computation accelerates significantly and the size of computation can be largely increased as a result of the parallelism. A passive contaminant point source was placed at the middle of the convective boundary layer to simulate the atmospheric dispersion. The requirement of the input of dispersion coefficients in k-theory and Gaussian models was replaced with direct input of turbulence flow data. It was found that the present numerical model can predict several non-Gaussian plume behaviours and the computed results agreed well with findings from experimental observations. © 1998 John Wiley & Sons, Ltd.     

高速公路封道施工路段交通流特性及通行能力分析——以杭州湾大桥内侧两条车道封道情形为例

基于交通流实测数据,针对三车道高速公路杭州湾大桥路段内侧两条车道因施工而封闭时的情形,建立元胞自动机交通流模型.根据公路养护安全作业规程和车辆行驶特点,细致划分了施工路段各区域,采用不同的换道规则来模拟不同区域中车辆的换道行为,区分车型和司机性格差异,模拟结果与实测数据吻合良好,验证了模型的有效性.通过数值模拟,研究发现封道时流量和速度随着进车率增加均有不同程度的下降,并且流量还会因施工区域长度的增加而下降.此外,通过分析封道时的道路服务水平评价指标与交通流特征值之间的关系,得出在三级服务水平以上时,道路通行能力能得到基本的保证,以此推荐了极限流量值,可为高速公路封道时的交通管理提供理论依据.