Thermal Plume Characteristics Of Building Facade And Its Influence On Local Thermal And Wind Environment

In recent years,in the context of global climate change,the rapid development of cities has also triggered a series of urban environmental problems.The dense distribution of tall buildings in modern cities has greatly reduced the city's ventilation capacity,resulting in frequent calm wind weather,the accumulation of heat and pollutants in urban areas is difficult to discharge,which in turn leads to increasing urban heat island effect and air pollution problems.At this time,the heat plume at the building scale is of great significance to urban ventilation,pollutant diffusion and the microclimate of the building complex.In this paper,a research method combining experimental testing and numerical simulation is used to study the thermal plume characteristics of the building facade.First,the scale ratio of the model was determined through similarity theory analysis,and the temperature and wind speed of the measuring point of the heating surface design of the model were tested under static wind conditions.The experimental results were processed and analyzed to determine the changes of wind speed and temperature in both horizontal and vertical directions under different experimental conditions.Then,comparative analysis of different types of turbulence equations,combined with the characteristics of the research object of this article,select the appropriate turbulence model.According to the building model used in the actual experiment,on the premise of ensuring the reliability and correctness of the calculation results,the geometric characteristics of the simulated objects are simplified and a reasonable calculation domain range is determined.Through grid independence verification,a reasonable number of grids is divided,and the correct boundary conditions are set in accordance with the experimental conditions,and the preparation of the simulation calculation is completed.Subsequently,Fluent software was used to simulate the thermal plume characteristics of the building facade under the same dimensions as the experimental model.Through the comparison of experimental data and simulation calculation results,the rationality of the established model and the correctness of the simulation results are successfully verified.On this basis,considering the static wind conditions,the actual building scale model was simulated and analyzed for the building thermal plume characteristics under three wall heat flux densities of 50 W / ?,100 W / ? and 200 W / ?.The results show that the effect of the heat flux density on the wall surface of the building on the heat plume is more pronounced in the areas closer to the surface and higher in the ground,but less affected in the areas farther from the surface and shorter in the ground.And,the influence range of building heat plume mainly depends on the building height,not the heat flux density of the wall.Finally,based on the simulation of the thermal plume characteristics of the building facade under static wind conditions,further study the influence of the thermal plume of the building facade on the local thermal environment and wind environment of the building under different wind directions and wind background wind conditions.The results show that: For the thermal environment,the wall temperature along the horizontal direction presents a sudden drop in the range of 1?2cm from the surface.Therefore,the scale of the thermal plume of the building on the local temperature field of the building is small,but for different wind speed and direction also have their own characteristics.For the wind environment,when the heating surface is the windward surface,when the wind speed reaches 2 m/s,the effect of the hot plume is not large;when the heating surface is the leeward surface,for the wind speed of 1.5m/s and 2 m/s,the height above the ground effect of the hot plume on the wind speed field at 10 m is negligible and can be ignored;when the wind direction is parallel to the heating surface,for the wind speed field at the top of the building,when the wind speed reaches 2 m/s,the influence of the hot plume can be ignored.The research results of this paper provide new ideas for the optimal design of urban ventilation,pollutant diffusion,and microclimate of buildings.