建筑热羽流影响下空气污染物跨楼层扩散特性

Diffusion characteristics of air pollutants across building floorsunder thermal plume effect

采用风洞实验和数值模拟,以单侧通风6层建筑为研究对象,考虑水平来流和太阳辐射引起的近壁面热羽流的耦合作用,探究了不同理查德森数Ri下建筑壁面热流运动、温度分布及污染物在竖直方向的跨楼层扩散传播特性。研究表明:当Ri≤5.64时,水平风力占主导,建筑2/3高度以下迎风面有明显的下行及向两侧的流动,1层释放的污染物对2层及以上楼层几乎没有影响,此时归一化净逃逸速度NEV~*基本保持不变;当Ri>5.64时,壁面热浮升力作用不能被忽略,随着Ri的增大,NEV~*明显增大,表明有更多污染物从1层室内扩散出来,沿迎风面向上运动的热流对高层室内产生影响,导致污染物跨楼层传播的风险增大。

Taking a 6-storey building with single-side ventilation as the research object,considering the coupling effect of horizontal flow and near-wall thermal plume caused by solar radiation,this study conducts the wind tunnel experiment and numerical simulation to investigate the heat flux movement on the building wall,the temperature distribution and the diffusion and transmission characteristics of pollutants across building floors in the vertical direction under different Ri.The results show that when Ri≤5.64,the horizontal wind is dominant,and there is obvious downwind and bilateral flow on the windward wall below 2/3 of the building height.The pollutants released from the first floor have almost no effect on the floors above the second floor,and the normalized net escape velocity NEV*remains basically unchanged.When Ri>5.64,the effect of wall thermal buoyancy cannot be ignored,and NEV*increases obviously with the increase of Ri,which indicates that more pollutants will diffuse from the first floor,and the heat flux moving upwind along the windward wall has an impact on the upper floors,resulting in increasing risk of pollutant cross-floor transmission.