Three-dimensional measurements of tree crown movement using an infrared time-of-flight camera
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RESEARCH ARTICLE
Three‑dimensional measurements of tree crown movement using an infrared time‑of‑flight camera Marilena Enuş1 · Ebba Dellwik2 · Jakob Mann2 · Horia Hangan1 · Adrian Costache1 Received: 13 April 2020 / Revised: 14 August 2020 / Accepted: 12 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The study of wind–tree interaction represents a challenge in fluid dynamics partly because the three-dimensional tree crown and its branch structure are dynamically adapting to the mean and turbulent wind components. With the advent of infrared technologies these complex, three-dimensional, real time interactions between wind and the response of a tree can be assessed. The present work makes use of a Microsoft Kinect V2, which incorporates an infrared time-of-flight camera, to capture images containing point cloud data of a single garden tree in turbulent winds. The raw output from the sensor is used to translate three-dimensional information into mean crown positions and projected frontal canopy areas. This novel infrared time-of-flight sensor technique facilitates a better understanding of the behaviour of the tree crown against wind speed. Overall, less movement and larger crown areas are observed at lower wind speeds. As the wind speed increases, a general shrinkage in area, more swaying and a smoothing of the crown edges are noted. Correlations between the observed wind force exerted on the tree and the displacement of the crown centre as well as between the wind force and the projected frontal canopy area are determined. The displacement and the drag force are positively correlated for all wind speeds. The drag force and frontal canopy area are positively correlated at low wind speeds and negatively correlated at higher wind speeds with a bi-stable phase between. The infrared time-of-flight sensor has demonstrated its capacity to provide real-time three-dimensional scanning of trees in a wind testing facility providing new insights into the complex wind–tree interaction problem.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00348-020-03053-y) contains supplementary material, which is available to authorized users. * Marilena Enuş [email protected] 1
Western University, London, Canada
Department of Wind Energy, Technical University of Denmark, Roskilde, Denmark
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Experiments in Fluids
(2020) 61:234
Graphic abstract
1 Introduction The response of a tree to wind is highly complex and thus challenging to describe and quantify. The wind-induced adjustments in the branches, foliage, and stem represent fundamental aspects of trees and is of importance for understanding their structural stability. This study outlines the changes in the crown structure in response to turbulent wind fields, using a technique which has not previously been used for this purpose. The characterization of wind-induced tree motion is of interest for many research fields such as biology, agronomy
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