Numerical simulation of dispersion in an urban street canyon: Comparison between steady and fluctuating boundary conditions

Over the years, the reliance on CFD to investigate air flow and pollutant dispersion has increased significantly and the majority of these studies have employed Steady Wind Boundary Conditions (SWBC) at the inlet of the computational domain. In reality, wind fluctuates both spatially and temporally and the numerical simulations do not accurately represent field or experimental measurements when the inlet condition is assumed to be constant. Therefore, the aim of the current research is to address the limitations of these existing studies, by developing Fluctuating Wind Boundary Conditions (FWBC). The FWBC are then compared to SWBC in order to determine their suitability in the investigation of air flow and pollutant dispersion in urban street canyons. Three-dimensional (3D) numerical simulations are performed using Large Eddy Simulation (LES). The FWBC produces more realistic results when compared to the frequently employed SWBC.