壁面绿化及热效应对浅型街谷内污染物扩散与转化的影响研究

Impacts of green walls and thermal effects on pollutant dispersion and conversion within shallow street canyons

采用经风洞实验验证的CFD数值模型,就壁面绿化和热效应对浅型街谷内污染物扩散和NO_(x)-O_(3)光化学转化的影响开展研究。考虑了4种壁面受热模式以及4种叶面积密度的壁面绿化模式,并采用臭氧消耗率衡量光化学反应的剧烈程度。结果表明,壁面受热会改变街道峡谷内的流动结构,背风面受热和地面受热能够增加峡谷内顺时针旋涡的尺度,迎风面受热会削弱该旋涡的尺度,全壁面受热则会破坏旋涡结构。壁面绿化的设置能够有效降低峡谷内平均温度,促进峡谷内旋涡结构的重构,并且不同程度降低平均臭氧消耗率。因此,壁面绿化对缓解城市热岛效应和光化学污染具有积极的意义。

The CFD model validated by wind tunnel experiments was used to study the impacts of green walls and thermal effects on diffusion of pollutants and the NO_(x)-O_(3) photochemistry within the shallow street canyons.Four wall heating scenarios and green walls with four leaf area densities were considered,and ozone depletion rate was used to measure the severity of NO-Ophotochemistry.Results show that wall heating can change the flow structure within the street canyon.Leeward wall heating and ground heating can increase the size of clockwise vortex within the canyon,the windward wall heating can weaken the vortex size,and whole wall heating can destroy the vortex structure.However,the setting of green walls can promote the vortex structure reconstruction,effectively reduce the average air temperature in the canyon,and reduce the average ozone depletion rate.Therefore,the green walls plays a positive role in alleviating urban heat island effect and photochemical pollution.