Study On The Influence Of Green Vegetation On The Surrounding Environment

With the increasing proportion of the urban population in the total population,urbanization has brought about many impacts on the natural environment of human life.Green vegetation have the functions of windbreak,sand fixation,air purification,cooling and humidification.Greening can improve the microenvironment and alleviate urban heat island effect.Scholars at home and abroad have done a lot of research on the resistance characteristics of tree crown and the effect of greening on alleviating the heat island effect.However,there are few experimental studies on the relationship between the morphological structure parameters of the canopy such as leaf area index,solid volume fraction and optical porosity and the influence of the morphological structure parameters of the canopy on flow resistance of the canopy.Most of the studies on the effect of cooling and humidification of trees are mainly measured in field.Few people have analyzed the relationship between cooling capacity and humidification by wind tunnel experiments,and there are few studies on the spacing of trees and the surrounding environment of green layout.Based on this,we have studied the following aspects:(1)Three common evergreen plants including osmanthus trees,camellia trees and coral trees,were used as experimental samples,the leaf area index,solid volume fraction and optical porosity were used to analyze the complicated morphology of vegetation canopy.Relationship between the morphological structure parameters of the canopy and the influences of the leaf area index,solid volume fraction and optical porosity on flow resistance of the canopy were studied by experimental data.The results show that leaf area index approximately has linear relationship with solid volume fraction,and leaf area index and solid volume fraction of canopy has power exponent relationship with optical porosity,respectively.A model expression between parameters of canopy morphological structure,the drag coefficient of the canopy and leaf area index was presented by regression analysis of experimental results,the prediction result obtained by this correlation expression has little deviation from the test data.(2)Three common evergreen plants including osmanthus trees,camellia trees and coral trees,were used as experimental samples,the effects of different wind speed and parameters of canopy morphological structure on the cooling and humidifying effect of canopy were studied through wind tunnel experiments.The definition of temperature reduction coefficient and humidity increasing coefficient was given.The correlation expressions between 3 kinds of canopy cooling capacity,humidification,temperature reduction coefficient and humidity increasing coefficient were obtained by fitting and regression of experimental data.The results showed that the effect of cooling and humidification in the wind tunnel was significant.The temperature difference between the 3 tree species was between 0~3? and the humidity increased between 0~2.2%.The correlation expression between the cooling capacity,humidification and wind speed and leaf area index is fitted well with the experimental data.(3)Using the macro method,the plant is regarded as a porous medium,and the source term is added to the plant by UDF.The flow field around the canopy is simulated,and VC6.0(Microsoft Visual C + + 6.0)is compiled to realize the coupling solution of the surface temperature of plant leaves,and the temperature field around the crown is simulated.The influence of tree planting spacing and greening layout on the surrounding environment was explored.The results show that the recommended planting spacing of trees is 8m~10m;Under the same greening rate and green rate,the layout of the side greening layout should be planted in front of the building and on both sides,that is,the layout three.