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Wind and Structures   Volume 22, Number 4, April 2016, pages 455-476
Wind direction field under the influence of topography, part I: A descriptive model
A.U. Weerasuriya, Z.Z. Hu, S.W. Li and K.T. Tse

Abstract     [Buy Article]
    In both structural and environmental wind engineering, the vertical variation of wind direction is important as it impacts both the torsional response of the high-rise building and the pedestrian level wind environment. In order to systematically investigate the vertical variation of wind directions (i.e., the so-called \'twist effect\') induced by hills with idealized geometries, a series of wind-tunnel tests was conducted. The length-to-width aspect ratios of the hill models were 1⁄3, 1/2, 1, 2 and 3, and the measurements of both wind speeds and directions were taken on a three-dimensional grid system. From the wind-tunnel tests, it has been found that the direction changes and most prominent at the half height of the hill. On the other hand, the characteristic length of the direction change, has been found to increase when moving from the windward zone into the wake. Based on the wind-tunnel measurements, a descriptive model is proposed to calculate both the horizontal and vertical variations of wind directions. Preliminarily validated against the wind-tunnel measurements, the proposed model has been found to be acceptable to describe the direction changes induced by an idealized hill with an aspect ratio close to 1. For the hills with aspect ratios less than 1, while the description of the vertical variation is still valid, the horizontal description proposed by the model has been found unfit.
Key Words
    descriptive model; hill terrain; wind characteristics; wind-tunnel test
A.U. Weerasuriya and K.T. Tse: Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
Z.Z. Hu: Department of Civil Engineering, Tsinghua University and Graduate School at Shenzhen, Tsinghua University, P.R. China
S.W. Li: Division of Ocean Science and Technology, Graduate School at Shenzhen, Tsinghua University, Shenzhen, P.R. China


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