基于绿地微气候的长沙太平街历史文化街区热环境数值模拟

Numerical Simulation of Thermal Environment in the Historical and Cultural District of Taiping Street Based on Greenbelt Microclimate

以长沙太平街历史文化街区为研究对象,首先对街道空间的现状微气候环境做分析,然后基于ENVImet软件进行数值模拟,并将研究区3种典型的街道空间的绿化优化方案的微气候数值模拟结果与基准方案的差值进行比较,进而阐释绿化优化方案的热环境调控程度。结果表明:1)随着太阳辐射逐时的变化,研究区域的热环境状况发生较大变化,在水平空间分布上呈“高温低湿”“低温高湿”特征。2)热环境质量与下垫面状况、风环境和建筑布局等因素的有关。3) 3种街道空间提高街区绿地面积均可大幅降低街区平均辐射温度,乔灌+立体(水体)复合型绿地类型的热环境优化调控作用在白天均要优于乔灌、乔草方案。在绿地率一定的情况下,商业空间绿地布局中由于绿化均匀分散布局产生的树荫面积覆盖街道空间的范围最大,热环境优化调控程度的排序为分散>平行>集中,而居住空间和广场空间受建筑布局影响,绿地布局在降温增湿同时应兼具良好通风效应,因此热环境优化调控程度最大为集中布局。

This study used the historical and cultural block of Taiping Street in Changsha as the research object.First the current microclimate environment of the street space was analyzed, then numerical simulations based on ENVI-met software were performed, which compared the microclimate numerical simulation results of three typical greening optimization schemes of the street space in the study area and the benchmark scheme, as well as explained the degree of thermal environment control of the greening optimization scheme. This study is expected to provide a reference for the reconstruction of urban historical blocks as well as optimization and control of the thermal environment. The results showed that: 1) With an hourly change in solar radiation, the thermal environment changed considerably, and the horizontal spatial distribution was characterized by "high temperature and low humidity" and "low temperature and high humidity." Thermal comfort is related to the underlying surface conditions, wind environment, building layout, and other factors. The low temperature and high humidity of the area with relatively concentrated green space along street spaces had a slow-release effect on the thermal environment. The ventilation effect of the area with the dense building layout was poor, and the thermal radiation of the underlying surface was high, affecting the heat dissipation and humidification in the research area. 2) The enclosed space layout of buildings in the study area caused building shadows and poor ventilation to affect the green space, which was not conducive for cooling and humidification. 3) Three types of greening transformation schemes were proposed for the street spaces of three different architectural layouts in the historical block of Taiping Street. The three kinds of street space green space optimization and benchmark schemes(the current street space situation) were simulated using ENVI-met microclimate simulation software. Optimization results showed that the same greening optimization scheme had different regulatory effects on the thermal environment in different building layouts. The three kinds of street spaces significantly reduced the average radiation temperature of the block by increasing the greening area of the block. The optimal regulatory effect of the thermal environment of the tree-shrub+three-dimensional(water) compound green space type was better than that of the tree-shrub and tree-grass scheme in the daytime. Under a certain green space ratio, the area of shade generated by the uniform and decentralized layout of green space in a commercial space covered the largest range of street space. The order of the degree of thermal environment optimization and control was decentralized>parallel>centralized. The residential and square spaces were affected by the architectural layout, and the green space layout should have good ventilation, cooling, and humidification effects;therefore, the maximum degree of thermal environment optimization and control is the centralized layout.