考虑浮升力影响的建筑群内线源污染扩散的大涡模拟

LARGE EDDY SIMULATION OF POLLUTANT DISPERSION WITH BUOYANCY INFLUENCE IN URBAN STREETS

针对浮升力存在的不稳定条件,在Kataoka方法基础上,通过调整阻尼函数来产生大涡模拟所需要的入流湍流条件。之后,应用标准Smagorinsky模型对处于不稳定边界层的建筑群内的线源污染扩散问题进行模拟。计算结果与风洞数据对比表明,在不稳定条件下,使用大涡模拟方法能够较为精准的预测流场变量的平均值及变量的脉动成分。最后,根据计算结果对街道峡谷内的空气流动和污染扩散进行了研究。结果显示:街道峡谷内的空气发生了循环流动,从而形成了一个大的涡系,对峡谷内的污染扩散产生了重要影响。

For unstable condition with the influence of buoyancy,the inflow turbulence was generated by adjusting the damping function based on Kataoka＇s method. Then large eddy simulation（ LES） of pollutant dispersion from a line source within urban streets was conducted by using standard Smagorinsky model. One objective of this study was to evaluate the accuracy of LES model for the simulation of thermal and pollutant dispersion phenomena. The calculated mean flow variables and their fluctuations showed favorable agreements with the wind tunnel experimental data under unstable condition. The air flow and pollutant dispersion behavior within street canyons were investigated according to the results of LES. The recirculating flow and a large vortex were formed in the street canyons,as a result the pollutant dispersion was much affected.