Study On "Cold Island Effect" Of Lakes In Suburbs And Its Scenario Simulation

The pace of urbanization is accelerating,and the development of urban suburbs has become an important strategic goal of urban development.Urban heat islands are gradually spreading from the center to the suburbs.The urban lake water body is a composite of the city's natural underlying surface and artificial underlying surface.It has an obvious "cold island effect",which to a certain extent is of great significance to alleviating the local heat island and improving the outdoor comfort of residents around the lake area.As an important development core of the Yangtze River Economic Belt,Changsha City has developed rapidly in recent years.The intensity of the urban heat island has been increasing year by year,and the scope of influence has gradually radiated to the suburbs of the city.This study focuses on the lakes in the suburbs of the city and the surrounding built-up areas,taking Tongsheng Lake in Changsha City as the research object,using parallel fixed-point measurement combined with CFD(Computer Fluid Dynamics)scenario simulation to explore the suburban lakes in summer The temporal and spatial variation of the "cold island effect" and its influencing factors,by controlling the changes of single factors,simulating the degree of influence of different factors on the "cold island effect" of lakes,and proposing optimization suggestions and measures to enhance the "cold island effect" of lakes in the suburbs of cities.The research results are helpful to improve the quantitative understanding of the "cold island effect" of lakes in suburban cities from the perspective of environmental physics,such as landscape architecture,urban planning and other professionals,and propose scientific and reasonable improvement measures.The main research contents and conclusions are as follows:(1)Overview and research on the "cold island effect" of urban water bodies.By summarizing the causes and related content of urban thermal environment,urban green space cold island effect,and urban water body "cold island effect",research ideas and technical routes are proposed.(2)Study on the changing law and scope of influence of the "cold island effect" of lakes in the suburbs of cities.In summer(June,July,and August),lakes in the suburbs of cities have a "cold island effect" on the surrounding environment,and the average daily temperature drop of the lake's water body is 0.55 ?.The cooling effect of the lake water body is most obvious at 0m from the lake shore,and the cooling range can reach 1.11?.The cooling effect on the downwind area is higher than that on the upwind direction and the vertical direction.(3)Research on the influencing factors of the "cold island effect" of lakes in the suburbs of cities.The distance to the lake,relative humidity and air temperature have a strong correlation,and they have a strong ability to explain the changes in the lake's"cold island effect".There is a correlation between the average building height,the percentage of impervious surface area,the percentage of green coverage,the percentage of trees,shrubs,grass,wind speed and air temperature,indicating that the temperature change at the measuring point is affected by the lake water body and the surrounding environment.(4)Scenario simulation study of "cold island effect" in lakes in the suburbs of cities.The CFD scenario simulation has a high degree of agreement with the measured data,and the correlation coefficient R2=0.8621,which is scientific and reasonable.The simulation study of the actual case study found that the "cold island effect" of lake water bodies is most obvious in the downwind area,and the vegetation area can block the airflow and have a cooling effect on the surrounding local environment.Through the simulation analysis of changing the single influencing factor,it can be seen that to a certain extent,the lake area is the main factor that affects the "cold island effect" of the lake.The water body has an accelerating effect on the airflow,reducing the lake water body area,and the cooling intensity of the lake water body on the surrounding environment is weakened.The scope of influence is reduced;increasing the height of the building affects the transmission and distribution of airflow,the wind speed in the flow area and the angular flow area increases,the wind environment quality in the leeward area of the building deteriorates,the air temperature around the building rises,and the diffusion range of water vapor Reduce;increasing the building retreat distance can optimize the wind environment of the lakeshore space,and improve the thermal comfort around the lake water body and the downwind area;increasing the building spacing has a significant effect on the change of the internal wind field in the densely built area,effectively improving the internal wind of the building Environment,hot and humid environment;the change of wind direction has obvious influence on the distribution of the "cold island effect" of the studied lakes.(5)Suggestions for optimization of urban lake district planning.Based on the relevant conclusions and research results of actual measurement and numerical simulation,an optimization strategy to enhance the "cold island effect" of lakes in the suburbs of cities is proposed.In the future,the planning and construction of lake areas in suburban cities should strengthen the protection of the existing lake shoreline,keep the natural form of the lake unchanged,and reserve a buffer zone at the edge of the lake.The landscape configuration around the lake area can appropriately increase the small water landscape and vegetation landscape,forming a "cold spot" and enhancing the microclimate effect of a local area.Reasonably regulate the development and construction of lake water bodies,comprehensively consider factors such as building height,building receding lake shore distance,building density,vegetation types,topographic height difference,etc.,and set up ventilation corridors around the lake area based on actual conditions to give full play to the "cold island effect" of the lake water body.