Sellier Damien, Fourcaud Thierry, Lac Patrick
UMR LRBB, Domaine de l'Hermitage, 69 route d'Arcachon, F-33612 Cestas Cedex, France.
Tree Physiol. 2006 Jun;26(6):799-806. doi: 10.1093/treephys/26.6.799.
A finite element model was developed to study the influence of aerial architecture on the structural dynamics of trees. The model combines a complete description of the axes of the aerial architecture of the plant with numerical techniques suitable for dynamic nonlinear analyses. Trees were modeled on the basis of morphological measurements that were previously made on three 4-year-old Pinus pinaster Ait. saplings originating from even-aged stands. Calculated and measured oscillations were compared to evaluate model behavior. The computations allowed the characteristics of the fundamental mode of vibration to be estimated with satisfactory accuracy. Inclusion of a topological description of the aerial system in a mechanical model provided insight into the effect of tree architecture on tree dynamic behavior. Simplifications of the branching pattern in the model led to overestimations of the natural swaying frequency of saplings by 10 to 20%. Inadequate values of stem and root anchorage stiffness resulted in errors of 10 to 20%. Modeling results indicated that aerodynamic drag of needles is responsible for 80% of the damping in the studied trees. Additionally, damping of stem movement is reduced by one half when branch oscillations are not considered. It appears that the efficiency of the dissipative mechanisms depends directly on crown topology.
开发了一个有限元模型来研究树冠结构对树木结构动力学的影响。该模型将对植物树冠结构轴的完整描述与适用于动态非线性分析的数值技术相结合。基于之前对三株4年生海岸松幼树进行的形态测量对树木进行建模，这些幼树来自同龄林分。比较计算和测量的振荡以评估模型行为。计算结果能够以令人满意的精度估计基本振动模式的特征。在力学模型中纳入树冠系统的拓扑描述，有助于深入了解树木结构对树木动态行为的影响。模型中分支模式的简化导致幼树自然摆动频率高估了10%至20%。树干和根部锚固刚度值不足导致误差为10%至20%。建模结果表明，针叶的气动阻力占所研究树木阻尼的80%。此外，不考虑树枝振荡时，树干运动的阻尼会减少一半。看来耗散机制的效率直接取决于树冠拓扑结构。
