建筑底层架空对行人高度处风环境及污染物扩散影响的数值模拟

Numerical simulation on the impact of ground floor overhead on wind environment and pollutants diffusion at pedestrian height

在规则建筑群内,考虑建筑底层的架空设计,利用realizable k-ε紊流模型数值模拟了6种工况下的风场和污染物浓度场,并采用时均风速比M_(VR)、风速面积占比A_(RSi)和无量纲浓度K等指标对行人高度处的风环境和污染物浓度进行了评价。建筑底层的架空设计能有效增加行人高度处的M_(VR),上游建筑的架空对M_(VR)的增加效果更显著。架空设计能减小低风速ARSi,增加中风速和中高风速A_(RSi),当建筑群中有2列及以上的建筑采用架空设计时,A_(RSi)的改善效果更好。当污染源位于建筑群上游地面时,架空设计对行人高度处的K分布影响不大,架空导致的回流使得污染物难以扩散至建筑群内,还会因其架空导致紧邻污染源的建筑迎风面行人高度处的K显著变小。

The wind field and pollutant concentration field in a regular building group incorporating the ground floor overhead were numerically simulated with realizable k-εturbulence model.The indicators including mean wind speed ratio M_(VR),wind speed area ratio A_(RSi)and dimentionless concentration K were adopted for evaluating the wind environment and pollutants concentration at pedestrian height in six cases.The design of ground floor overhead can effectively increase M_(VR).It is more remarkable in the upstream buildings.The overhead also can reduce A_(RSi)at low wind speed while increase ARSi at medium and high wind speed.When there are two or more columns of overheand in the building group,better improvement of A_(RSi)can be achieved.The overhead design has little impact on the K distribution at pedestrian height when the pollution source is on the upstream ground of building group.Due to the strong backflow by overhead,it is difficult for upstream ground pollutants to diffuse in the downstream building group.In the building nearby pollution source,there is a significant decrease of K by the design of overhead at pedestrian height on the windward side.