Wind Tunnel Experimental Study on Air Pollutant Transportation and Dispersion for Hilly Terrain
|Keywords||hilly terrain air pollution transportation and dispersion wind tunnel experiment|
In this paper, experimental studies in wind tunnel were carried out on rules of airpollutant transportation and dispersion for hilly terrain. with three oncoming flowvelocity 1 m/s, 2.3 m/s and 3.6 m/s, the simulation tests of single hill and lengthwaysdual hills were carried out in a low-speed blow down wind tunnel, in whichsmoke-seeding flow visualization and PIV technology have been used.It is found that,(1) the transportation and dispersion rules of air pollution havedifferent state as the free oncoming flow velocity changes. The dispersion range ofsmoke is more wider in the normal(vertical)direction with low free oncoming flowvelocity, while the range is more smaller when the velocity is higher; the free streamvelocity affects the air pollution’s normal dispersion height, but have no affection forthe spanwise dispersion range; The position of air pollution concentration’s maximalvalue moves downstream when the free oncoming flow velocity becomes higher.(2)There is two separated vortex movement on the windward side and leeward side ofhilly, which make the effect of transportation and dispersion more stronger,theconsistence becomes lower, especially at the windward side of hilly peak.(3)At thehalf of hilly, the concentration changes more clearly as the velocity changes, when thevelocity is 1.0 m/s, the windward concentration is higher than leeward concentration;when the velocity is 2.3 m/s, the windward concentration is similar with leewardconcentration; when the velocity is 3.6 m/s, the windward consistence is lower thanleeward. The windward concentration is higher at the velocity 1.0 m/s than that at thevelocity 2.3 m/s, the leeward concentration is lower at the velocity 1.0 m/s than that atthe velocity 2.3 m/s. (4) Because of the effect of hill’s block to airflow, a periodicantisymmetric Karman vortex appears, which makes the concentration’s change has abig scale fluctuation with the period of 0.4s.