| With the development of economy and society,improvement of people’s living standards, ambient air quality problems has become increasingly concerned by people. Since the end of last century, China’s major cities have been in a rapid increase in vehicle population, thus leading to a shift in the Urban Air Pollution from coal-burned pollution in the past to the soot, complex motor vehicle exhaust pollution. Vehicle exhaust has become a major factor affecting the quality of urban atmospheric environment. In recent years, many scholars have conducted a lot of researches on the harm and diffusion regulations of cities’vehicle exhaust. However, plateaus city motor vehicle lanes flow field and wind tunnel researches are infrequent, which is caused by its high altitude, low air pressure, a relatively large surface roughness of the terrain and other special weather conditions, making the vehicle exhaust has its own unique diffusion law. Therefore, research on plateau mountainous city flow field law is necessary.Flow field calibration was carried out in environmental wind tunnel of Kunming University of Science and Technology in this study, including measurements of wind speed range, dynamic pressure stability, uniformity of airflow, airflow angle and turbulence. The results are shown that the maximum wind speed of the wind tunnel is 30.7m/s, higher than the designed wind speed 30m/s; due to the environmental impact, dynamic pressure stability index of breeze’s speed is poor. At the speed of 17m/s, the dynamic pressure stable coefficient is 0.76%; turbulence in each measuring wind speed is less than 0.5%; in the middle wind speed range, each measuring point airflow angle is between-0.5°～0.5°; at each wind speed of 0.2-5m/s,84% of all measuring airflow angle points are between-0.5°～0.5°; In the airflow uniformity measurement, middle wind speed in each measuring wind speed is less than 0.5%, meeting the requirements of the technical requirements; as influenced by the environment, part of the measuring point failed to meet the technical requirements.This article is intended for high altitude mountainous city (regarding Kunming, Yunnan Province as the research object), including models make for Kunming city with the scale of 1:3000. The wind tunnel flow field was adjusted according to the results of Wujiaba wind profile, so as to simulate the local flow field characteristics under neutral conditions in the wind tunnel model by arranging roughness elements segment, adjusting air bar and wind speed, achieving the on-site wind profile exponent similar to the wind tunnel simulation and simulating the road-wind angle of 0°,45° and 90°, corresponding to different height wind flow field at different distances in different situations, which obtained different points experiments wind profile exponent was in the scope of 0.28-0.39. Experiments measuring points are arranged at different intervals of the effects of different terrain conditions to wind speed, the results are shown that different building conditions and the height-width ratio make different points of wind speed and wind profile exponent different.FLUENT was employed to analyze the wind flow field characteristics under Road-wind angle of 45°, and the three-dimension model is set up for it by the CATIA 3D modeling software, meshing with ICEM analog area and selecting neutral stability conditions as boundary conditions, using SIMPLEC algorithm equations discretized and solved. The results show that the building windward wind speed and pressure is greater than the downstream flow field and the wind speed at rough ground is smaller. FLUENT simulation results with the regional flow field simulation of wind tunnel testing law has a relatively better consistency. Simulation results shown that relative error of wind profile exponent in each measuring points in between-2.93% and 5.17%, which in good agreement to the wind tunnel experimental results. |
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