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In situ drag coefficient measurements for rooftop trees

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Title: In situ drag coefficient measurements for rooftop trees
Authors: Koizumi, Akio Browse this author →KAKEN DB
Shimizu, Misato Browse this author
Sasaki, Yoshihisa Browse this author
Hirai, Takuro Browse this author
Keywords: Drag coefficient
Windthrow resistance
On-site measurement
Picea abies
var. japonica
Issue Date: Aug-2016
Journal Title: Journal of Wood Science
Volume: 62
Issue: 4
Start Page: 363
End Page: 369
Publisher DOI: 10.1007/s10086-016-1556-5
Abstract: To evaluate the drag coefficients for roof-top tree crowns, previously-developed field test methods for monitoring wind speed, wind direction, and stem deflection were improved using solar cells as a source of power. A field test was conducted for a Norway spruce and a shirakanba located on a rooftop. The drag coefficients showed large variations during low wind speeds, which were caused by the flexural vibration of the tree trunk due to the fluctuating wind speed. To compensate for this effect, the upper percentage of drag coefficients obtained for the 0.5 m/s wind speed classes were used for the exponential regression for drag coefficient as a function of wind speed. As a result, a conservative evaluation of drag coefficients for a greater range of wind speeds could be established instead of using all data. The drag coefficients at 30 m/s wind speed were estimated to be 0.594 for the Norway spruce, and 0.154 for the shirakanba using the upper 50% of the data. The exponential function convergence was more gradual for the spruce than for the shirakanba, which may be affected by a difference in the streamlining behavior.
Rights: The final publication is available at
Type: article (author version)
Appears in Collections:農学院・農学研究院 (Graduate School of Agriculture / Faculty of Agriculture) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 小泉 章夫

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