A novel canopy drag coefficient model for analyzing urban wind environments based on the large eddy simulation

Abstract

It is very challenging to capture the drag effects for the computational fluid dynamics numerical simulations of the urban canopy wind environment. This study proposed a novel canopy drag coefficient model for accurate analysis of the urban wind environment based on a large eddy simulation, where the drag coefficients varied with quantitatively identified canopy parameters along with the height. Four computational parameters, namely the average kinetic energy, turbulent kinetic energy, sub-grid scale turbulent kinetic energy, and sub-grid scale dissipation, were incorporated into the conventional drag coefficient. The Meixi Lake International Community in Changsha, China, was considered as a case study. The inlet boundary conditions were provided by the Weather Research and Forecasting model, and the proposed drag coefficient model was utilized to simulate the wind field characteristics. The results showed that the drag coefficient was relatively large near the ground, and it decreased with the increase of height overall. The decay rate of the drag coefficient below 0.4 times the building was significantly higher than the other areas. Finally, compared with the field measurement data, the proposed model had good accuracy of the simulated wind field compared to previous approaches, thus offering a reliable model for analyzing the urban wind environment.