Impacts Of The High-rise Residential Building Concave-Convex Plane Form On Single-sided Ventilation And Pollutant Concentration

With the urbanization in China,the density and population of the cities are increasing,resulting in environmental problems,such as heat island effect,traffic pollution.Environmental problems in urban space have become an important factor that affecting people’s health.While people spend most of their time indoors,the indoor air quality has great impact on human health.In China,natural ventilation is considered as an effective strategy to improve indoor comfort and air quality of residential buildings.The indoor air environment of a natural ventilated room depends on the outdoor microclimate,especially the wind speed,temperature,pollutant concentration and so on.The outdoor wind and thermal environment and the pollutant concentration are closely related to the indoor environment.As a component connecting indoor and outdoor,building envelope has an influence on indoor and the surrounding outdoor environment due to its shape,material properties and other parameters.Therefore,the ideal model combining "street canyon"-"indoor" was used to study the correlation between outdoor wind and heat environment and traffic pollution sources on natural ventilation and pollutant concentration in indoor residential buildings.In this study,open-sourced numerical Simulation software EnergyPlus and OpenFOAM were used to build a one-way coupling Computational model between BES(Building Energy Simulation)and CFD(Computational Fluid Dynamics).It is found that the distribution of surface temperature in the street canyon is different at four typical time during the day.When the inlet wind speed exceeds 2m/s,the thermal buoyancy caused by the diurnal change of surface temperature has no significant effect on the air flow in the street canyon.However,when the inlet wind speed is 0.5m/s,the thermal buoyancy has a crucial influence on indoor natural ventilation and pollutant concentration.Based on the survey and statistics of residential buildings in major cities of the hot summer and cold winter districts in China,the residential buildings built in recent five years are mainly high-rise buildings.And the application of single-side ventilation in high-rise residential buildings is still common,accounting for 43%.Besides,the south facade of the high-rise residential often appears in concave-convex design.By CFD simulation calculation and analysis,it is found that the setting concave-convex design have little influence on the natural ventilation and pollutant concentration of the crossing ventilation room.But it indeed has significant influence on the single-sided ventilation room.Based on these results,the concept of building plane concave-convex features is proposed and quantified in view of regular notch design and concave-convex changes of residential buildings.According to the relationship with the long axis of the street canyon,the plane concave-convex characteristics are divided into Vertical Roughness parameter(Rv)and Horizontal Roughness parameter(Rh).In the wind-heat environment,the concave and convex features of residential buildings facing the street are deeply studied and analyzed.The results show that the two parameters of plane concave-convex features have different effects on the natural ventilation and pollutant concentration of different rooms under different wind direction conditions.In this study,the influence of plane concave-convex characteristics on indoor natural ventilation efficiency was evaluated by air exchange rate.For the room with relative convex position,Rh is the dominant influencing factor under vertical wind.In parallel wind,Rv is the dominant influencing factor.For the room at the notch,the dominant factors under both wind directions were just opposite to those in the room at the convex position.Therefore,the concave and convex features should be discussed in detail according to the prevailing wind conditions of the city location and the room position when the building plane design is aimed at improving the indoor natural ventilation.Besides,in the study on the influence of pollutant concentration,it is found that the room at the lower floors are most affected by traffic pollutants.Under the two wind direction conditions,Rh is the dominant factor of pollutant concentration in the room at convex location,while Rv is the dominant factor of the room at notch.And for residential buildings facing the street affected by traffic pollution,appropriately reducing Rh and increasing Rv can reduce the influence of traffic pollution on the indoor environment.