Wind Tunnel Experiment Of Air Pollutant In Yuxi Central Urban Area

With the development of economy and society, urban functional area and industrial structure are all changing greatly, and air pollution gains complexity. The enacted new air quality standard shows our country and social public having paid more and more attention on ambient air quality problems. Yuxi central urban area lies on the southwest plateau area of China. The behavior of dispersion is unique because of the complex terrain, the big surface roughness, and low air pressure in plateau mountainous city. The air quality of this region has been always good. The research of atmospheric pollution is still at a relatively weak position, and the research of ground-level flow field observation and wind tunnel experiment in this area has not been carried out. Therefore, conducting research in this aspect is necessary.This article is intended for high altitude mountainous city (regarding Yuxi central urban area, Yunnan Province as the research object). The pilot balloon observation system with dual theodolite was used to investigate the effect of ground-level flow field characteristics, including atmospheric stability, wind-elevation relationship and wind profile exponent. The experimental results showed that the frequency of very unstable, unstable, weakly unstable, neutral and stable atmosphere was 1.52%,31.82%,25.76%,36.36%,4.54% respectively. The wind changed quickly. Wind speed-elevation relationships were observed as irregular type, normal type, extreme value type, reverse type and invariable type, and the frequencies were 45.45%、30.91%、 16.36%、5.45%、1.82% respectively. The wind profile exponent of this area is high. It is 0.608, 0.527 respectively at the neutral, unstable condition.The primary means of study on air pollutant diffusion regularity in Yuxi central urban area was wind tunnel experiment. A model of this region with a proportion of 1:3000 was made by wood, foam and plastic floss. It was placed in test section of wind tunnel. Onsite data of wind profile was used to regulate the wind profile of wind tunnel by regulating wind tunnel velocity, arranging rough-baffles and situating wind poles. It is found that the wind profile can be increased rapidly by adjusting the height and horizontal spacing of rough-baffles.C2H4 was used as tracer in wind tunnel tracing experiment, and fan-station was used to sample different points in the downwind area. The spatial and ground concentration of checkpoints was worked out by dilution ratio. The tracing experiment result showed that the variation of concentration with the transverse and vertical distance is normal distribution. But the transverse distance at 500m was skew distribution because of the high terrain of the east. The horizontal and vertical diffusion equation worked out on the basis of ground and spatial concentration. As the big surface roughness and high wind profile exponent, coefficient and index of horizontal diffusion equation were a little bigger than P-G’s.