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Wind and Structures
  Volume 30, Number 6, June 2020 , pages 597-616

Large eddy simulation of blockage effects in the assessment of wind effects on tall buildings
Yang Gao, Ming Gu, Yong Quan and Chengdong Feng

    The blockage effect on the aerodynamic characteristics of tall buildings is a fundamental issue in wind tunnel test but has rarely been addressed. To evaluate the blockage effects on the aerodynamic forces on a square tall building and flow field peripherally, large eddy simulations (LES) were performed on a 3D square cylinder with an aspect ratio of 6:1 under the uniform smooth inflow and turbulent atmospheric boundary layer (ABL) inflow generated by the narrowband synthesis random flow generator (NSRFG). First, a basic case at a blockage ratio (BR) of 0.8% was conducted to validate the adopted numerical methodology. Subsequently, simulations were systematically performed at 6 different BRs. The simulation results were compared in detail to illustrate the differences induced by the blockage, and the mechanism of the blockage effects under turbulent inflow was emphatically analysed. The results reveal that the pressure coefficients, the aerodynamic forces, and the Strouhal number increase monotonically with BRs. Additionally, the increase of BR leads to more coherence of the turbulent structures and the higher intensity of the vortices in the vicinity of the building. Moreover, the blockage effects on the aerodynamic forces and flow field are more significant under smooth inflow than those under turbulent inflow.
Key Words
    blockage effect; large eddy simulation; tall building; aerodynamic forces; flow field
Yang Gao, Ming Gu, Yong Quan and Chengdong Feng: State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, P.O. Box 200092, Shanghai, PR China

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