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A Practical Computational Fluid Dynamics Approach for Structural Engineering: Simulation of Approach Flow with Reduced Blockage Ratios



Yunjae Hwang, DongHun Yeo


Computational fluid dynamics (CFD) simulations for structural wind engineering applications require a fully developed boundary layer approach flow with horizontal homogeneity and zero pressure gradient for accurate characterization of wind loading on a structure. Previous studies have focused on achievement of such requirements primarily in computational domains whose heights are equal to or less than the atmospheric boundary layer (ABL) height, despite the need of a computational domain taller than the ABL height for certain applications such as buildings in an urban environment/or topographic surroundings to ensure an acceptably low blockage ratio. Thus, the current study proposes a novel procedure for the generation of the fully developed, horizontally homogeneous and zero pressure gradient flow in a vertically extended computational domain above the ABL height with using Reynolds-Averaged Navier-Stoke (RANS) simulations. The proposed procedure is applied to simulations with an isolated building and topographic models, respectively, to investigate the blockage effects on the flow field in the vicinity of the models and associated wind loading on their surfaces. The results demonstrate successful creation of the approach flow that satisfies those three requirements for CFD simulations in structural wind engineering and applicability to scale-resolving CFD simulations including large-eddy simulations (LES).
Technical Note (NIST TN) - 2275
Report Number


Approach flow simulation, atmospheric boundary layer (ABL), blockage ratio, computational fluid dynamics (CFD), horizontal homogeneity, horizontal pressure gradient, Reynolds-averaged Navier-Stokes (RANS), structural engineering, wind engineering.


Hwang, Y. and Yeo, D. (2023), A Practical Computational Fluid Dynamics Approach for Structural Engineering: Simulation of Approach Flow with Reduced Blockage Ratios, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed May 21, 2024)


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Created November 2, 2023