Study Of Building Facades Temperature-rise Effect On Near-wall Wind Field And Pollutant Dispersion

Wind environment includes two interrelated part,outdoor’s and indoor’s.With the growing number of high rise building and the increasing building density,the wind environments becomes an important factor in deciding the quality of life.On one hand,the quality of wind environment around buildings has significant effected on pedestrian comfort even safety.On the other hand,wind environment assessment has been a critical issue in the design and the research on it will contribute to the wind environment analysis systematization and theorization.The flow field around the actual building are very complex,with the variation of the upcoming wind conditions,the shape of building even the temperature rise may affect the flow structure.This article mainly focus on evaluating how the solar radiation effects the flow filed and the pollutant dispersion around the building.The building facades with different temperature rise in the neutral atmospheres has been simulated and the flow field around the building was analyzed.Firstly,3 RANS turbulence models are employed to simulate outdoor environment,by the comparison between the simulated results and the wind tunnel experimental provided by the Architectural Institute of Japan(AIJ),the optimal turbulence model for the numerical simulation of outdoor wind environment around a building is determined.The results show the Realizable model is the best due to its high accuracy of modeling air flow and the pollutant diffusion.Then,it has been applied to simulate the building with different temperature rises,the results show that the velocity and the concentration fields near to the building facades varied with different temperature rises.In addition,a series of simulations involved a single cubic obstacle normal to the mean wind direction and one upwind source of C2H4 are carried out.And the source located at different lateral positions with the building facades at different temperatures have been studied,the results show the combined effect of position and temperature is hard to discuss phenomenologically.And because of the complex of the effect,the change of the concentration shows disorder.However the results of the research contribute to guide window opening.Secondly,this paper also has studied the coupled outdoor and indoor air flow under the condition of windows opening.Accurate CFD simulation of coupled ventilation is essential for design and evaluation of natural cross-ventilation strategies for building.It widely recognized that CFD simulations can be very sensitive to the lager number ofcomputational parameters.This paper presents a series of coupled 3D steady RANS simulation for a generic isolated building.The CFD simulation are validated based on detail wind tunnel experiments with Particle Image Velocimetry by Blocken.The computational parameters including the size of the computational domain,the resolution of the computational grid,the inlet turbulent kinetic energy profile,the turbulence model is investigated.The accuracy and reliability parameters are determined.Then,building with different opening positions and temperature rise has been simulation,and the ventilation performance has been studied.It has a guiding role in the design of building ventilation strategy and building closed windows.