The Microclimate Research Of Low-rise And High-density Settlements In Small Towns

With the development of urbanization of small towns,there are many big blocks,wide roads,and large and tall buildings in the planning.The construction mode of small towns is influenced by big cities,and the original lowrise and high-density traditional town texture is destroyed,causing the living environment is low in comfort and vitality.In order to change this situation,this thesis takes the relationship between Zhoutie Town’s urban morphology and its microclimate as the research object,and explores the urban morphology suitable for the construction of small towns in the future.Firstly,outdoor microclimate,outdoor thermal comfort and its relationship with urban morphology,low-rise and high-density settlements,and other related studies are reviewed,found that the existing research lacks effective evaluation of outdoor thermal comfort reflecting the comprehensive performance of urban design.Therefore,an index that can dynamically describe the comfort of the overall space throughout the day is proposed—CZR(Comfort Zone Ratio)and the sOTCA(Spacial Outdoor Thermal Comfort Autonomy)proposed by Nazarian,for outdoor microclimate evaluation.Secondly,through literature review,urban morphology mapping and microclimate monitoring,the microclimate of low-rise high-density and other urban morphologies were simulated and studied,There are five forms of the Zhoutie historical settlements,high-rise settlements,multi-story settlements,and ideal high-rise and low-rise high-density morphologies were extracted.Use ENVI-met for numerical simulation,and use sOTCA and CZR to compare and analyze each urabn form.It is found that Zhoutie historical settlements perform well in both winter and summer: the comfortable areas in winter are mainly distributed in courtyards with an aspect ratio of less than 0.3,which can block the wind and obtain sufficient sunshine;the comfortable areas in summer are mainly distributed in the north-south street,the street walls on both sides can achieve a good shading effect,and at the same time,it is parallel to the dominant wind direction in summer to achieve a good ventilation and cooling effect.However,the ideal high-rise settlements morphology performs poorly in both winter and summer.Then,starting from the existing low-rise and high-density urban morphology,the ideal form of the low-rise and high-density townhouse is extracted.In two combination methods of A and B,four aspect ratios of H/W=9:6,H/W=9:9,H/W=9:12,H/W=9:15,two orientations of N-S and NE-SW,A total of 32 working conditions were simulated in winter and summer both.The results show that the combination method,aspect ratio and orientation all have an impact on the comfort of the microclimate in winter and summer: in order to achieve ideal comfort conditions,the form of increasing sunshine and blocking wind can be adopted in winter,shading and enhanced ventilation should be adopted in summer.However,Zhoutie Town is located in an area with hot summer and cold winter.Therefore,the urban morhpology of winter and summer under ideal and comfortable conditions is inconsistent or even contradictory.To solve these problems,improvement measures at the two levels of the single courtyard and the the texture of the settlements were proposed: at the single courtyard level,by reducing the height of the building cornice on the south side of the courtyard to increase winter sunshine,and adjusting the direction of overhead corridors to improve summer Ventilation;in terms of the texture of the settlements,the enclosed courtyard can significantly improve the thermal comfort in winter.The vertical courtyard can get almost the same level of sunshine as the horizontal courtyard in winter,and can have better shading effect in summer.The above research results provide theoretical and data support for the study of microclimate in small towns residential settlements,and provide reference for the construction of small towns residental settlemets in the future.