城市建筑群环境有毒有害气体扩散数值模拟

Numerical Simulation of Hazardous Gas Dispersion Around Buildings in Urban Environment

摘要:

应用计算流体力学(CFD)原理和方法建立街区尺度点源泄漏扩散的数值模型，并经风洞试验结果验证其正确性.对街区建筑物扰动和两种来流风速（1.5 m?s-1，3.0 m?s-1）下近地面气云扩散过程及特性进行模拟与分析.结果表明：给定合适的计算参数，基于RNG k—ε模型和SIMPLE算法能够有效模拟复杂障碍物条件下有毒有害气体的扩散过程；近地面气云扩散受道路、建筑物布局和来流风速的影响明显，建筑物周围测点浓度同该处源距、方位、高度以及风向偏离程度存在密切联系；较大的来流风速加快气云水平输送，同时有利于浓度的稀释；泄漏停止后建筑物密集区间浓度稀释相对滞缓，可能对人群健康构成威胁.

Abstract:

A street level computational fluid dynamics (CFD) model was established to simulate the movement characteristics of the released gas and the concentration distribution around the complex arrangement of buildings. A wind tunnel experiment about release and dispersion in building array was used to validate the model. Then numerical simulations were carried out with two different reference wind speeds, 1.5 m?s-1 and 3.0 m?s-1, in a genuine urban area. The results show that, given appropriate parameters, the RNG k—ε closure and SIMPLE algorithm can be employed to predict the dispersion process accurately in obstacle terrain. The time varying concentration distributions near the ground highlight the influences of wind speed, road and building arrangement, on the dispersion. The sampling concentration around buildings is strongly affected by the positions of sampling points relative to source, including height, distance from the source, angle from wind direction, and so on. The higher wind velocity speeds up plume propagation, as well as concentration dilution process. The results also confirm that, among dense buildings the hazardous gas may stay much longer, which constitutes a threat to public health and safety.