考虑羽流浮力影响的高层建筑周围污染物扩散数值模拟

Computational Fluid Dynamics Simulation of Pollutant Dispersion Around a High-Rise Building Considering Effect of Plume Buoyancy

摘要:

考虑了由环境空气和气体污染物之间的密度差异所产生的不同羽流浮力效应的影响，采用大涡模拟（LES）方法对一个高层建筑周围的污染物扩散问题进行了数值模拟研究。通过将模拟结果与风洞试验结果对比，验证了LES方法的准确性；同时，讨论了不同羽流浮力对平均浓度分布、浓度输运机制以及浓度脉动的影响。轻质气体所受的正浮力使建筑后方尾流区内竖向对流及湍流通量明显增大，从而增强了污染物的稀释作用；而重质气体在负浮力的影响下则产生相反的效果。除此之外，向上的羽流浮力使浓度脉动进一步增强，而向下的羽流浮力则对其有一定的抑制作用。

关键词:污染物扩散;羽流浮力;高层建筑;大涡模拟;浓度脉动

Abstract:

In this paper， large-eddy simulations （LES） were conducted to investigate the pollutant dispersion around a high-rise building， with different plume buoyancies produced by the density difference between ambient air and polluted gas being considered. The accuracy of the numerical method used in this paper was validated by comparing the simulated results with the wind tunnel experiment data. The effects of different plume buoyancies on the time-averaged concentration， concentration transportation， and concentration fluctuation were discussed. The positive buoyancy of the light gas significantly increases the vertical convection and turbulent flux in the wake region behind the building， enhancing the dilution of pollutant. In contrast， heavy gas has an opposite effect under the influence of negative buoyancy. In addition， the upward plume buoyancy further enhances the concentration fluctuation， while the downward plume buoyancy suppresses it to some degree.

Key words:pollutant dispersion;plume buoyancy;high-rise building;large-eddy simulation;concentration fluctuation