The Research On The Change Of Temperature Effect Of Urban Lake Based On CFD Model

In recent years,the speed of urban development has made the property of urban underlying surface change obviously,and the problem of urban thermal environment is increasingly serious.The urban lake has a significant effect on improving the urban thermal environment due to the basic characteristics of its water body.Based on the 400m site of the lake surrounding the Hunan Martyrs Park,this paper investigates the mechanism and the change rule of the temperature effect of the city lake by using the method of fixed-point measurement and CFD numerical simulation,and finds the leading factors affecting the temperature effect.The main research contents are as follows:(1)The concepts of the lake temperature effect,the present research situation and the theoretical basis are summarized and analyzed,and the basic characteristics of the water body and the mechanism of regulating the temperature in the city lake are discussed.(2)The diurnal variation law,seasonal difference law,influence range and dominant factor of lake temperature effect are studied by parallel fixed-point measurement.The results showed that the lake had a cooling effect in spring(April and May),Summer and autumn,and the summer cooling effect was the strongest,the average cooling rate was 1.75?,the autumn cooling effect was slightly weak,the average cooling rate was 0.99?,the Spring(April and May)was the weakest,and the average cooling The lake in spring(March)and winter to the surrounding temperature effect,January,the strongest warming effect,the average temperature of 1.26 ?,Spring March,the average temperature of 1.09 ?,the winter February temperature effect is the weakest,average temperature 0.58 ?;The type and effect of the lake temperature effect are obviously correlated with the daytime temperature,which is not related to the variation amplitude of daytime temperature.During the spring,summer and autumn season the highest daytime temperature(13:00-15:00),the most effective cooling effect,in the lowest temperature period(8:00-9:00 or 17:00-18:00)cooling effect is the weakest.In spring March and winter,the maximum temperature in the time period is the weakest,and the warming effect is strongest at 8:00.The effective range of lake temperature effect on surrounding environment is not invariable,and different distribution laws are presented in different seasons and months.(3)The influence of the dominant factors on the temperature effect of Summer lake was studied by CFD numerical simulation analysis and single factor change respectively.The results show that the size of lake area is proportional to the effect intensity and influence range of lake temperature effect at certain scale.When the lake area is zero,the study area wind speed increases the 0.15-0.3m/s,the study area overall temperature rise amplitude is 0.6-4?,in which the lake periphery and the lower wind direction area warming 2.4-4 ?,explained the summer lake daytime to the lower wind direction area cooling effect is most obvious.When the lake area is reduced to half,the wind speed in the study area is not obvious and the wind speed distribution is almost unchanged.In the study area,the temperature is rising 0.8-2.4?,the temperature distribution is almost consistent with the actual model,the lake has a cooling effect on the surrounding area,but due to the decrease of the lake area,the cooling effect and the influence range are weakened,among which the temperature of the water and surrounding area is the most obvious,and the Next is the lower wind direction area,the temperature 0.9-1.2?,the influence to the upper wind direction area is smallest,the warming 0.5-0.9?.The influence of the temperature effect on the vertical direction of the lake also decreases.The range of temperature effect above the lake is reduced from 80m to 60m,and the effect of Summer lake temperature is less than that of changing the back distance of the building and removing the buildings or buildings near the lake shore without changing the building density and building layout.The influence range and the intensity of the summer lake cooling effect are obviously related to the height of the surrounding buildings.The higher the surrounding buildings,the weaker the cooling effect of the lake on the periphery,and the lower the range of the vertical and horizontal direction.Without reducing the number of buildings in the surrounding area of the lake and not controlling the height of the building,A single increase in the space between the buildings in the buildings will increase the range of radiation impact on the surrounding area,making local heating,and the improvement of the temperature effect of the lake is not strong.The aim of this paper is to study the change rule and mechanism of the temperature effect of the lake,which can better exert the effect of the temperature regulation of the city lake on the surrounding environment,and bring some enlightenment to the planning method and construction idea of the surrounding area of the city Lake,and provide some reference value.At the same time,we hope to make more use of CFD simulation software in the future urban development and planning,and simulate the thermal environment and wind environment in the construction area,and try to avoid the bad influence of the unfavorable factors in the development on the thermal environment,and contribute to the improvement of the bad thermal environment of the city.