Wind tunnel simulation of wind loading on low-rise structures: a review

Abstract

A review of existing and new considerations for the assessment of wind loads on low-rise structures from wind tunnel simulation experiments is presented. Attention is given to the aerodynamics of surface-mounted prisms, followed by a discussion of the atmospheric flow characteristics near the surface under a variety of atmospheric and upwind terrain conditions. In the final section, detailed recommendations and requirements are presented for the appropriate conduct of these experiments. The content of this article provides detailed justification for wind tunnel simulations based primarily on the duplication of the turbulence intensities and small-scale turbulence of the incident flow. In order to satisfy the latter requirement, it is recommended to utilize models of low-rise buildings that have a scale not smaller than 1:50. Less emphasis should be placed on duplication of the integral scale of the turbulence, as duplication of both scales requires equality of the Reynolds number that cannot be achieved in wind tunnels. Duplication of either the Jensen number ( H/ z o) or the power-law exponent of the mean velocity profile is insufficient to guarantee the proper duplication of the necessary turbulence parameters. For homogeneous upwind terrain and near-neutral stability, the pertinent turbulence parameters can be obtained from basic principles without the use of empiricism. For terrain with scattered upwind obstacles (Δ x>15), the turbulence parameters can be obtained above the blending height with the use of the “regional” roughness length. For a closer spacing of the roughness obstacles (Δ x<15), the displacement height should be included in the analysis to obtain values of the turbulence parameters. For all situations, the simulation of the turbulence in the atmospheric surface layer should be based on duplication of the pertinent flow parameters above the blending height. Comparison of either flow or pressure measurements requires that both the sampling rate and record length be properly matched in model and full scale. Comparison of peak pressure coefficients is only meaningful if they have the same level of probability.