Modeling and analysis of highway emission dispersion due to noise barrier and automobile wake effects

Abstract

Highway automobile emissions is an important environmental issue and can be complex due to the influences of multiple factors such as noise barrier configurations, vehicle induced wake flows, and traffic flow conditions. To better understand this phenomenon, a three-dimensional computational fluid dynamics (CFD) model has been developed and implemented to simulate the automobile emissions dispersion under various conditions. The model was first validated by comparing simulation results of velocity and emission concentration with data from a wind tunnel experiment in the literature. Furthermore, simulation and analysis revealed that with the existence of noise barriers, the automobile wake region was enlarged, the flow recirculation zone was enhanced, and the emission concentration level was increased. In addition, vehicle body geometry effects were simulated and analyzed. Results showed that the maximum turbulent kinetic energy can be observed on the upper and lower surfaces of a vehicle due to the shear layer and flow separation. For different vehicle body geometry with slant angle effects, turbulent kinetic energy and the concentration of emission around the vehicles were reduced. Traffic speed, another major factor in highway automobile emissions in general, resulted in more emissions remaining on the highway in congestion cases. Simulation results from this research will help to find possible solutions to solve this environmental issue by obtaining a better understanding of highway automobile emissions through the analyzation of the effects of noise barrier configurations, vehicle induced wake flows, and traffic flow conditions.