Simulation And Optimization Of Urban Mesoscale Regional Wind Environment Based On CFD

In recent years,with the rapid development of economy and the acceleration of urbanization,the city presents a development trend of high density,high height and high intensity,which significantly weakens the urban air flow,leads to the accumulation of heat and pollutants,and the urban environmental problems become increasingly serious.Therefore,it is particularly necessary to strengthen urban ventilation and enhance the wind comfort of urban environment.At present,the research on urban wind environment mainly focuses on the influence of factors such as the geometric form and architectural layout of single buildings and architectural groups on the wind environment at the micro scale.However,the true diversity of urban environment construction layout,architectural forms and the interaction of building wind environment is complex,and because of the lack of urban meso-scale regional complex building space form of pedestrian outdoor wind environment impact of related research,the research achievements of building wind environment in the urban construction in the actual application,it is difficult to guide the optimization of urban wind environment.To solve this problem,this paper selected Tsuen Wan,Hong Kong as a case study area,and carried out a real scale(1:1)simulation study of urban mesoscale regional wind environment using CFD method.On this basis,the influencing factors of urban pedestrian wind environment are analyzed,and the optimization strategy of wind environment is put forward,which can provide practical guidance for planning practice to enhance urban wind comfort.The details are as follows:First,the CFD numerical model of urban mesoscale region is established and verified.Based on building vector data,the grid model of urban building spatial form is established,and the parameters such as numerical simulation model,boundary condition,solution method and discrete scheme are determined based on the best practice guidelines(Best Practice Guidelines,BPGs)for wind engineering,.Compared with the wind tunnel test data,the reliability and validity of the CFD numerical model are verified.Secondly,the CFD numerical simulation of urban wind environment is carried out.Based on three prevailing winds(easterly,northerly and northeasterly)in the case area(Tsuen Wan,Hong Kong),this paper studies the whole wind environment and the pedestrian wind environment in the low-rise,high-rise and super-high-rise buildings,and obtains the complex wind field characteristics in Tsuen Wan,Hong Kong,as well as the detailed construction flow around the city.It is proved that the CFD numerical model established in this paper can describe the urban wind environment in the mesoscale area in detail.Thirdly,the influencing factors of urban pedestrian wind environment are analyzed.Through qualitative and quantitative analysis,it is found that there is a strong positive correlation between the average building height,scattered degree and the wind speed ratio at pedestrian height.There is a strong negative correlation between building density and wind speed ratio at pedestrian height.Finally,the wind environment optimization strategy is proposed and applied from two aspects of building group height and building density.According to the analysis of the influence factors of urban building space form on the wind environment,the wind environment optimization strategy of optimizing the building combination height and reducing the building density was adopted to significantly improve the pedestrian wind speed level and pedestrian wind comfort in the region.After optimization,the pedestrian comfort zone in the study area increased by 6.21%,and the comfort zone in the low-rise,high-rise and super-high-rise buildings increased by 18.42%,9.79% and 11.02%,respectively.