The Research Of Multi-scale Urban Ventilation Channel Construction Method And Planning Strategy

Urban climate is a major topic that affects urban sustainable development.With the urban built-up area is increasing,the urban problem,such as urban air pollution and urban heat island effect,has become increasingly prominent.Urban managers and planners put forward urban ventilations channel,to improving the problem of ventilation.The practice shows that reason-able the planning and construction of urban ventilations channel helps to promote the urban and the suburban area of air circulation,thereby reducing the urban heat island effect,and improving air quality.At present,the domestic research and application of urban ventilations channel started relatively late,there are still many problems to be solved and improved.The purpose of this paper is improves the urban wind and thermal environment and dis-cusses urban ventilations channel construction method and planning strategy.First,combing the urban ventilations channel related basic theory.Secondly,research on the spatial pattern of Xi’an wind and thermal environment,and the potential of ventilation in urban areas,with the comprehensive utilization of related theory which urban planning,meteorology,geographic in-formation science and computational simulation technology.Finally,constructing three differ-ent scales urban ventilations channel that are city territory scale,urban area scale and neighbor-hood scale,and proposing the planning guidance of urban ventilations channel under different scales by applying urban design method.(1)For a long time,the sprawling urban development mode causes the nature of urban underlying surface to change continuously,and seriously affects the urban ventilation effect.The construction of urban ventilations channel is conducive to enhancing the urban ventilation efficiency,and improving the urban wind and thermal environment.(2)Through the research on urban background wind-thermal environment and the urban ventilation potential in Xi’an city,it shows that:①From 1951 to 2016,the average annual tem?perature of Xi’an city range from 12.6℃ to 15.9℃ but the overall characteristics of tempera-ture change in turn showed slowly decrease,overall smooth,significantly increased.②The spatial distribution of surface temperature in Xi’an is different in summer,and concentrated high temperature zones are located on Lianhu district,Beilin district,Xincheng district,Changan district.The spatial range of heat island effect in the northern region of main urban zone is larger and more concentrated,relative to the southern region.③Taking the bell tower as the center,east-west and north-south direction of the heat island intensity decrease in turn from the industrial area,commercial area,centralized villages and general residential area.④Urban construction density is relatively large.Construction area and no construction area were 255.7km2 and 480.9km2 in development boundary,of which high density building area ac-counted for 36.1%.⑤Urban roads and prevailing wind direction showed moderate consistency,and they are conducive to urban ventilation on the whole.⑥Urban ventilation potential is high.Open space in 3rd Ring Rd,such as Bahe,Darning palace ruins and Han Changan ruins,have become potential wind compensation district,and open space out of 3rd Ring Rd is a potential source to urban well ventilation.(3)The research methods of urban ventilations channel planning under different scales are quite different.In the paper:①The spatial pattern of Xi’an wind field is simulated,based on WRF/UCM model,to construct the two stage ventilations channel under the regional scale:4 city territory scale primary ventilations channel and 6 city territory scale secondary ventilations channel.②Construction of two stage urban area scale ventilations channel which are 4 urban area scale primary ventilations channel and 4 urban area scale secondary ventilations channel,by applying Minimal Cost Path(MCP)method that based on urban ventilation potential model.③The wind field spatial pattern at different heights in the study area is simulated,by applying Computation Fluid Dynamics(CFD),and the two scale neighborhood scale ventilations channel that are 3 neighborhood scale primary ventilations channel and 4 neighborhood scale secondary ventilations channel,are extracted on the basis of 5m height wind speed nephogram.