大涡模拟建筑物对近源大气污染物扩散的影响

采用大涡模拟(LES)方法对一个由上风低源排放的烟流在孤立建筑物周围扩散的现象进行了数值模拟。模拟中,离散网格的尺度控制在100倍Kolmogorov湍流尺度的量级以内,亚格子应力由Smagorinsky模型加以模拟,并采用了随机数方法生成符合指定湍流特征的入流边界条件。数值模拟结果表明:建筑物尾流区平均浓度场的分布和大小不仅取决于局地流场的影响,在很大程度上也受到因建筑物阻挡出现的烟流抬升和马蹄涡对烟流的捕获的影响。通过对比风洞试验数据显示:大涡模拟方法能较好地再现气流绕建筑物的流动形态和建筑物周围的浓度分布,因而具有广泛的应用前景。

Effects of Buildings on Pollutant Dispersion From a Nearby Source by Means of Large-eddy Simulation

With the Smagorinsky subgrid model and the transport equation, a large-eddy simulation was carried out for the dispersion of a plume, which was emitted from an upwind low-level source, around an isolated building. In this simulation, mesh density was controlled within 100 times Kolmogorov microscale and the inflow condition with specified turbulent characteristics was generated by random number method. The simulation demonstrates that the distribution and magnitude of mean concentration in the wake region of the building was influenced not only by local flow patterns, but also by plume rise due to building blockage as well as by plume captured by horseshoe vortices. In comparison with results from wind-tunnel experiments, it shows that the LES can reproduce flow patterns and concentration distribution around the building well to reflect the effects of buildings on pollutant dispersion.