Evaluation of turbulent length scale within urban canopy layer based on LES data

In this study, a new evaluation method was developed for the turbulent length scale using large-eddy simulation (LES) data. An LES was performed on the wind flow over urban-like roughness elements with periodic boundary conditions to investigate the influence of urban configurations on turbulent characteristics within the urban canopy layer. Spatial distributions of the grid scale turbulent kinetic energy (kGS) and mean strain rate (Sij) were obtained from the LES results, and the value of the turbulent length scale was estimated from the kGS and Sij values. A modeling approach previously proposed by the authors to reproduce the influence of urban configurations on the turbulent flow field within the canopy layer in a Reynolds-averaged Navier-Stokes simulation was examined by using the spatial distribution of the turbulent length scale provided by the LES data.