Wind tunnel tests have been conducted on a 1:75 scale model of a Sitka spruce forest in a correctly scaled turbulent boundary-layer flow. 12000 tree models were manufactured with mass, flexibility and aerodynamic drag characteristics chosen to give dynamical similarity with typical 15 m trees in a 30ms−1 gale. To measure the dynamic response of a sample tree, set within this model forest, a miniature, fast response strain-gauge balance was designed and built. Linked to a computer for on-line data sampling, this balance provided measurements of the fluctuating along-wind and acrosswind components of the overturning moment at ground level, leading to values of mean and extreme moments and the frequency spectrum of the sway motion. Associated measurements of local wind flow characteristics were made with hot-wire anemometers and a laser anemometer. The response of the tree has the characteristics of classical lightly damped vibration and there is evidence that resonant sway motion increases the extreme overturning moments significantly above the values produced by wind gust forces alone.
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Department of Engineering Science, Oxford University, UK
G. R. Stacey, R. E. Belcher & C. J. Wood
Northern Research Station, Forestry Commission, Roslin, Midlothian, UK
B. A. Gardiner
Stacey, G.R., Belcher, R.E., Wood, C.J. et al. Wind flows and forces in a model spruce forest. Boundary-Layer Meteorol 69, 311–334 (1994). https://doi.org/10.1007/BF00708860
Revised: 04 November 1993
Issue Date: May 1994
DOI: https://doi.org/10.1007/BF00708860
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