Simulation Model And Analysis Of Influence Of Water Body On Thermal-humid Climate In The Surrounding Area Of Xi'an Urban Area

In recent years,China's urbanization speed,urban population continues to grow,construction land expands unceasingly,and different from the rural land cover materials,energy consumption,emissions and other reasons,formed the city and the suburbs of the temperature difference,namely the "urban heat island".Urban heat island effect is a great harm,the most intuitive is the impact of urban high temperature on human comfort,but also exacerbate air pollution,resulting in abnormal weather and natural disasters.As one of the underlying surfaces of urban,water can improve the environment and regulate the climate.The existing research on water and urban hot climate is basically independent of each other,or a small range of research on the impact of water on the thermal environment,can not reflect the city's overall hot and humid environment,the establishment of urban scale water and atmospheric heat and moisture exchange model is imperative.In this paper,the author analyzes the natural conditions and the development situation of Xi'an,using electronic maps and other Internet tools,as little as possible in the case of resources,the geometric model of the study area(ie,Xi'an city within the high speed)about urban construction,water bodies and road is established in the true scale size.On the other hand,the principles and formulas of water and heat exchange in the atmosphere are summarized,and the model of heat and moisture exchange suitable for this topic is extracted.The program is introduced into Fluent by UDF function and verified.Coupled the Xi'an city model with the above water and atmosphere heat and moisture exchange model,and the numerical simulation model of urban scale is established.The three cases were numerically calculated,and the calculation results are analyzed from three aspects: wind speed,temperature and relative humidity.The conclusions are as follows: in the wind aspect,the wind speed of the urban suburbs(such as the Hancheng and Qujiang ruins and other)is significantly greater than that of the old city within the city walls in the northeast wind(EN),and the wind speed in downwind area is higher than that in upwind area.The wind speed above the water body is obviously larger than that of the non-water body,but the water body has little effect on the wind field above the city 'soverall height of 15 m.Increasing the wind speed can increase the speed of the whole wind field accordingly.In the temperature aspect,the existence of the water body has a cooling effect on the air above it,and plays a role in improving environment temperature of downwind area.The temperature influence of the vertical direction of the water body is related to its area and the height of the building distribution.Increasing the wind speed can Improve the influence of the water body on the downwind direction,and the cooling range increases.In the relative humidity aspect,the existence of water is a significant role in the humidification above it,and will increase the relative humidity in downwind area.In the vertical direction,the humidification of the water body decreases with height.However,the water vapor gets more uniform diffusion with the decrease of the density of the building community,and the wind speed spreads faster.Due to the large density of the main urban area in Xi'an,coupled with the dominant wind direction for the northeast wind,the most harmful to the southwest region of the city,resulting in a small wind speed,high temperature,and low relative humidity in this area.Finally,based on the analysis of the results of this study,some suggestions are made to improve the urban hot and humid climate: to avoid the high height of the building at the crossroads so as to reduce the resistance of the airflow to the vertical direction and improve the ventilation at the same time can make the city heat spread better;along the main wind direction of Xi'an to build artificial lake or repair existing water,so that the role of the cold source of water to get better play;In the planning of the area,the design of the building and the water should be combined with the main wind direction to establish the ventilation corridor,control the ventilation corridor on both sides of the building density and height,so that the urban suburbs of wind energy flows through the water,the low temperature and humidity To the city center and the main wind direction of the downstream area;urban residential area of the staff,the heat generated,so in the district planning stage,you can reasonably arrange a number of artificial water body to improve the thermal environment of the district,while avoiding the formation of negative pressure zone,resulting in decreased air quality.