Simulation Model And Analysis Of The Ventilation Environment In Urban Of Xi’an

In recent years, as a high speed of urbanization in our country and sustainable growth of urban population, urban construction land expands constantly and the problem of urban land resources shortage is more prominent. Now there are two features of the new building in urban. One is the high of the building is much higher than existed before, the other is the density of building is much greater. The wind Environment of urban faces a great challenge because of a lot of tall buildings and a cluster of buildings. To a great extent, Urban wind environment affects the city residents’ quality of life, since drafting efficiency directly affects the renewal speed of the air in cities and the speed of pollutants discharge. Besides, it can relieve urban heat island. So existing single building and small scale numerical model already can’t reflect the overall urban complex ventilation environment, city scale model is imperative.This article firstly expounds and analyses urban ventilation status of Xi’an from the geographical environment, natural climate, building distribution and road network structure of Xi’an. In a deeper step, establishing an urban scale geometric model of buildings and roads in urban inside the freeway of Xi’an with real size and the simulation model of urban ventilation based on Google maps and street view maps,in the case of taking up less resources. Simulating the urban ventilation environment of Xi’an from three conditions, such as the dominant wind direction EN of summer and the dominant wind direction ENE of winter. And analyzing the result of simulation from four aspects as wind velocity, pressure, temperature and ventilation rate.At last, some proposal are discussed related to improving urban ventilation based on the result in this paper. The height of buildings at the crossroads should be limited and the layout of the buildings are set as “chamfering shape” if it is possible, such as the layout of Zhonglou Restaurant, Kaiyuan Shopping Mall and Zhonglou Post at the crossroads around the bends of Zhonglou in Xi’an, which can reduce air flow resistance in vertical direction. When planning of the region, the ventilation corridor is built consideration of the dominant wind direction to control the density and height of the building on both sides of the ventilated corridor, leading the wind to better flow to urban center and the downstream of the dominant wind direction. The personnel density is often relatively larger in urban residential area, so the high-rise residential buildings should be layout properly to optimize the wind environment and avoid forming negative pressure inside the residential area, which can lead the air quality worse.