Effect of Incoming Turbulent Structure on Pollutant Removal from Two-Dimensional Street Canyon |
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| Authors: | Takenobu Michioka Ayumu Sato |
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| Institution: | 1. Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646 Abiko, Abiko-shi, Chiba-ken, 270-1194, Japan
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| Abstract: | Large-eddy simulations are conducted to investigate the effects of the incoming turbulent structure of the flow on pollutant removal from an ideal canyon. The target canyon is a two-dimensional street canyon with an aspect ratio of 1.0 (building height to street width). Three turbulent flows upwind of the street canyon are generated by using different block configurations, and a tracer gas is released as a ground-level line source at the centre of the canyon floor. Mean velocity profiles for the three flows are similar, except near the roof. However, the root-mean-square values of the velocity fluctuations and the Reynolds shear stress increase with the friction velocity of the incoming turbulent flow. The spatially-averaged concentration within the canyon decreases with increasing friction velocity. Coherent structures of low-momentum fluid, generated above the upwind block configurations, contribute to pollutant removal, and the amount of pollutant removal is directly related to the size of the coherent structure. |
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