Spatiotemporal distribution of traffic emission based on wind tunnel experiment and computational fluid dynamics (CFD) simulation

Abstract

With the increasing urbanization and motorization, transportation has become one of the primary sources of carbon emission and air pollution, causing serious diseases to city residents. This study focuses on assessing pollutant dispersion patterns under multi-scenario situations and verifying the effectiveness of computational fluid dynamics (CFD) numerical simulation model using wind tunnel experiments and field measurements. A single-vehicle model was built to obtain the spatiotemporal distribution of Carbon Monoxide (CO) concentrations around the vehicle. Pressure coefficients of monitoring points were measured to compare with the values from the wind tunnel test. Then, numerical simulations were extended to car-following platoon and empirical street canyon scenarios. On-site measurements were carried out to ensure that the CFD model reflects the actual flow field around a vehicle in a certain precision range for given experimental design. The results indicated that the traffic-related pollutants were concentrated in the semicircle with the exhaust pipe as the center, with a radius of 1.5 m behind the vehicle. The podium building structure in the street perpendicular to the prevailing wind direction tends to induce the deposition of pollutants at the corner and bottom of the podium. Exhaust concentration at the right-angle area of a podium building on the leeward side of the wind direction is 221.1% higher than that in the windward side. Findings of this study may shed light on the street architecture design and the future applications of CFD model to estimate pollutant concentration along urban street canyons, thus to eventually improve urban environmental sustainability.