Large Eddy Simulation of Vehicle Induced Turbulence in an Urban Street Canyon with a New Dynamically Vehicle-Tracking Scheme

ABSTRACT

Moving vehicles could have a considerable influence on air flow and turbulence within urban street canyons, especially the vehicle induced turbulence (VIT), which is an important consideration for pollutants’ dispersion and local air quality management. To simulate air flow in urban street canyons with moving vehicles, an Euler-Lagrangian method was further developed by this study. The method involved dynamically tracking each moving vehicle and determining the vehicle induced drag force on surrounding air. Simulations under different background wind velocities and vehicle speeds show that, moving vehicles could pose a strong effect on wind turbulence, but have a lesser effect on average wind field within a street canyon. The presence of VIT was mainly in the lower areas of a street canyon. The average standard deviation of velocity (σ_w0) in the lower areas is about 0.5 m s^–1. In comparison with theoretical and experimental VIT models, VIT values produced by our simulations were higher than those obtained by experimental model, and were slightly lower than those produced by theoretical model. Instantaneous air flow fields within a street canyon were also investigated. Our results have indicated that the existence of local eddies could be a contribution factor to VIT.