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环境科学学报 2012
The influence of the ground heating on the diffusion capability in street canyon under different air temperature stratification conditions
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Abstract:
Based on the computational fluid dynamics (CFD) method, the influences of air temperature stratification and ground heating on the flow field and the diffusion process in street canyon are studied. Aiming at two kinds of street canyons with depth-width ratios of 0.5 and 1.0, respectively, 18 numerical sensitivity tests are performed. The results of the numerical tests show that the ground heating plays a more important role than the air temperature stratification in the pollutant diffusion process in street canyon. The analysis shows that ground heating is able to remarkably promote the diffusion capability in the street canyon. When ground heating exists, the variations of the flow structure, the air exchange rate and the turbulence intensity generally tend to be favorable in removing the pollutant in the street canyon. Even under the condition of stable stratification, thermal circulation induced by ground heating is also able to transport and disperse the pollutant out of the street canyon, and consequently leads to the dropping of the pollutant concentration near ground.