Large-scale coherent structure and canopy-level turbulence in the convective boundary layer over urban areas

Zhou，Kangcheng1,2; Liu，Chun Ho2; Wan，Minping1

2023-10-01

10.1016/j.buildenv.2023.110733

Building and Environment   影响因子和分区

0360-1323

1873-684X

Thermally unstable stratification alters the winds over urban areas and excites organized, large-scale motions (LSMs) in the atmospheric boundary layer (ABL). The current understanding of the interaction between urban turbulence and buoyancy-induced coherent structures is rather limited due to their multiscale, multiphysics nature. Nine sets of large-eddy simulation (LES) are performed to critically examine the influence of atmospheric instability on turbulent boundary layers (TBLs) interacting with idealized urban roughness elements. Varying the stratification from neutral to almost free convective conditions enables the coherent structures to transit from horizontal rolls to open cellular patterns. The aerodynamic roughness parameters tend to decrease in more unstable stratification, potentially a result of buoyancy effects that might enhance organized ejections and suppress energetic sweeps within the roughness sublayers (RSLs). Unexpectedly, roughness-induced sweeps dominate the vertical momentum fluxes within urban canopies even under the most convective condition. However, decoupling the momentum and heat transports in highly convective states results in a subtle influence of urban roughness on the vertical heat fluxes therein. The spatial distribution of canopy-level turbulent momentum fluxes is found to be strongly modulated by the overlying large-scale coherent structures. The modulation is enhanced with increasing instability. In addition, urban-like surfaces elevate the large-scale rolls and assist them in forming under a weaker stratification than in canonical settings.

Coherent structures Roughness sublayer (RSL) Shear-buoyancy interaction Surface fluxes Urban turbulence

SCI ; EI

英语

第一 ; 通讯

National Natural Science Foundation of China[12225204];Guangdong Science and Technology Department[2019B21203001];Guangdong Science and Technology Department[2020B1212030001];

Construction & Building Technology ; Engineering

Construction & Building Technology ; Engineering, Environmental ; Engineering, Civil

WOS:001076996500001

PERGAMON-ELSEVIER SCIENCE LTD

20233714701635

Atmospheric boundary layer ; Atmospheric thermodynamics ; Atmospheric turbulence ; Boundary layer flow ; Large eddy simulation ; Momentum ; Multiphysics ; Surface roughness ; Turbulent flow ; Urban transportation

Highway Transportation:432 ; Railroad Transportation:433 ; Atmospheric Properties:443.1 ; Fluid Flow:631 ; Fluid Flow, General:631.1 ; Thermodynamics:641.1 ; Mathematics:921 ; Mechanics:931.1 ; Physical Properties of Gases, Liquids and Solids:931.2

ENGINEERING

2-s2.0-85170066774

Scopus

1.Department of Mechanics and Aerospace Engineering,Southern University of Science and Technology,Shenzhen,Guangdong,China
2.Department of Mechanical Engineering,The University of Hong Kong,7/F, Haking Wong Building, Pokfulam Road,Hong Kong

Zhou，Kangcheng,Liu，Chun Ho,Wan，Minping. Large-scale coherent structure and canopy-level turbulence in the convective boundary layer over urban areas[J]. Building and Environment,2023,244.

Zhou，Kangcheng,Liu，Chun Ho,&Wan，Minping.(2023).Large-scale coherent structure and canopy-level turbulence in the convective boundary layer over urban areas.Building and Environment,244.

Zhou，Kangcheng,et al."Large-scale coherent structure and canopy-level turbulence in the convective boundary layer over urban areas".Building and Environment 244(2023).