Finite element analysis of trees in the wind based on terrestrial laser scanning data
Finite element analysis of trees in the wind based on terrestrial laser scanning data
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DOI：
10.1016/j.agrformet.2018.11.014
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发表时间：
2019-02-15
影响因子：
6.2
通讯作者：
Malhi, Y.
中科院分区：
文献类型：
--
作者：
Jackson, T.;Shenkin, A.;Malhi, Y.
风害是森林结构和动态的重要驱动力，但对天然阔叶林的了解甚少。本文提出了一种新的研究风害的方法：地面激光扫描（TLS）数据和有限元分析相结合。根据TLS数据重建树木的最新进展使我们能够在机械模拟中准确地表示树木的3D几何形状，而无需费力的手动映射或简化对树木形状的假设。利用该模型预测了英国Wytham Woods的21棵树的树干上产生的机械应变，并使用这些树木上测量的应变数据进行了验证。对于风速计附近的5棵树的子集，该模型预测了5分钟的应变时间序列，其平均互相关系数为0.71，受当地测量的风速数据的影响。此外，该模型很好地预测了与5 ms（-1）或15 ms（-1）风速相关的最大应变（分别为N = 17，R-2 = 0.81和R-2 = 0.79）。我们还预测了临界风速时，树木将打破从现场数据和模型，并找到一个很好的整体协议（N = 17，R-2 = 0.40）。最后，该模型预测正确的趋势，在基本频率的树木（N = 20，R-2 = 0.38），虽然有一个系统的预测不足，可能是由于简化处理的材料性能的模型。目前的方法依赖于当地的风数据，因此必须与风流动模型相结合，才能适用于大尺度或复杂地形。这种方法适用于地块水平，也可以应用于开放式生长的树木，如城市或公园。
Wind damage is an important driver of forest structure and dynamics, but it is poorly understood in natural broadleaf forests. This paper presents a new approach in the study of wind damage: combining terrestrial laser scanning (TLS) data and finite element analysis. Recent advances in tree reconstruction from TLS data allowed us to accurately represent the 3D geometry of a tree in a mechanical simulation, without the need for arduous manual mapping or simplifying assumptions about tree shape. We used this simulation to predict the mechanical strains produced on the trunks of 21 trees in Wytham Woods, UK, and validated it using strain data measured on these same trees.For a subset of five trees near the anemometer, the model predicted a five-minute time-series of strain with a mean cross-correlation coefficient of 0.71, when forced by the locally measured wind speed data. Additionally, the maximum strain associated with a 5 ms(-1) or 15 ms(-1) wind speed was well predicted by the model (N = 17, R-2 = 0.81 and R-2 = 0.79, respectively). We also predicted the critical wind speed at which the trees will break from both the field data and models and find a good overall agreement (N = 17, R-2 = 0.40). Finally, the model predicted the correct trend in the fundamental frequencies of the trees (N = 20, R-2 = 0.38) although there was a systematic underprediction, possibly due to the simplified treatment of material properties in the model. The current approach relies on local wind data, so must be combined with wind flow modelling to be applicable at the landscape-scale or over complex terrain. This approach is applicable at the plot level and could also be applied to open-grown trees, such as in cities or parks.