Large-eddy simulation of turbulent flow and structures within and above an idealized building array

Abstract

In this research, wall-modeled LES has been performed to investigate turbulent flow in an idealized urban environment comprised of an array of rectangular buildings (MUST array). An inflow condition based on generation of grid turbulence is utilized to mimic the turbulent approaching boundary layer at the inlet of the computational domain. The numerical approach has been validated by comparing the first- and second-order statistical moments of the turbulent flow field against the available water-channel measurement data. Turbulent coherent flow structures, energy spectra, and budget balance of the resolved kinetic energy are investigated. With the aid of the dynamic nonlinear subgrid-scale (SGS) stress model, the backscatter of the kinetic energy from small to large scales of flow motions is also studied. It is found that the scatter of kinetic energy is sensitive to the presence of the building obstacles. As the elevation increases, the ratio of the SGS dissipation rate to the viscous dissipation rate remains stable under the backward scatter condition but varies significantly under the forward scatter condition.