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.

中文翻译：

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使用红外飞行时间相机对树冠运动进行三维测量

风-树相互作用的研究代表了流体动力学中的一个挑战，部分原因是三维树冠及其分支结构动态适应平均和湍流风分量。随着红外技术的出现，可以评估风和树木响应之间这些复杂的、三维的、实时的相互作用。目前的工作利用 Microsoft Kinect V2，它结合了一个红外飞行时间相机，在湍流风中捕获包含单个花园树点云数据的图像。传感器的原始输出用于将三维信息转换为平均树冠位置和投影的正面冠层区域。这种新颖的红外飞行时间传感器技术有助于更好地了解树冠对抗风速的行为。总体而言，在较低风速下观察到较少的运动和较大的树冠区域。随着风速的增加，注意到面积普遍收缩，更多的摇摆和冠部边缘变得平滑。确定了观察到的施加在树木上的风力与树冠中心位移之间以及风力与投影的正面冠层面积之间的相关性。对于所有风速，位移和阻力都呈正相关。阻力和正面冠层面积在低风速下呈正相关，在较高风速下呈负相关，两者之间存在双稳态。红外飞行时间传感器已证明其能够在风力测试设施中对树木进行实时三维扫描，从而为复杂的风-树相互作用问题提供新的见解。