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.
Highlights
A growing trend of urbanization and land surface modification is occurring because over half of the world’s population lives in urban areas, and this is projected to increase by two-thirds by 2050 [1]
The detailed velocity profile graph is shown in Appendix A
Drag coefficient models that do not consider the turbulence component cannot be adapted for simulating the wind field features near the Previous studies about the drag coefficient on the fluid in urban canopy usually consider the mean wind
Summary
A growing trend of urbanization and land surface modification is occurring because over half of the world’s population lives in urban areas, and this is projected to increase by two-thirds by 2050 [1]. Lien and Yee [25] considered the turbulent kinetic energy (TKE) and average kinetic energy (AKE) to obtain the drag coefficient distribution at different heights; the drag coefficient distribution near the ground was not reported. Drag coefficient models that do not consider the turbulence characteristics cannot be adapted for simulating the wind field characteristics of a ground surface with complex geometry. It is clear that studying the drag coefficient near the ground by considering the turbulence characteristics has theoretical and practical significance To address this issue, a novel urban drag coefficient model that incorporates several key parameters, i.e., the AKE, TKE, sub-grid scale (SGS) TKE, and dissipation, was proposed based on the large eddy simulation (LES) approach in this study. Obtaining the drag coefficient cd is challenging, and a detailed analysis of the drag coefficient for an urban canopy is discussed below
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