鹅掌楸树叶在风中的变形与振动

发布时间：2018-05-18 09:17

本文选题：树叶 + 形状重构　；参考：《力学学报》2017年02期

【摘要】：树叶的空气动力与流固耦合特性研究在树木保护、新发电技术开发、太阳能帆板设计等方面具有重要意义.Vogel首次发现树叶在较高风速下具有形状重构以避免受损害的能力.Vogel实验时叶柄端部是简支的,与叶柄与树枝的自然连接方式不同.在本文的研究中,叶柄端部是固支的,叶片垂直悬挂,正面或反面迎风.在风速0～27 m/s范围内,存在两种叶片静止状态,即飞翼形稳定和锥形稳定;还有3种叶片振动状态,即低频摆动、第1和第2高频振动.这5种状态由5个临界风速决定.通过70余片树叶测试结果的统计,得到了树叶每个状态存在的概率,及每个临界风速的期望值.流动显示发现树叶变形后其尾流中存在旋涡脱落现象.天平测量发现叶片阻力系数随叶片雷诺数的增大而减小并逐渐接近于0.1.引入悬臂梁模型,采用测量的叶片气动力,对叶柄静态弯曲形状进行计算,结果表明当风速由0逐渐增至5 m/s时,叶柄向下游弯曲迅速;但风速由5 m/s进一步增大时,向下游的弯曲则变慢.
[Abstract]:Study on aerodynamic and fluid-solid coupling characteristics of leaves in tree protection, new power generation technology development, Vogel found for the first time that leaves have the ability of shape reconstruction to avoid damage under higher wind speed. In Vogel's experiment, the tip of the petiole is simply supported, which is different from the natural connection between the petiole and the branch. In the present study, the tip of the petiole is fixed, the blade is suspended vertically and the front or opposite is upwind. In the range of 0 ~ 27 m / s of wind speed, there are two kinds of blade static states, namely, flying airfoil stability and conical stability, and three kinds of blade vibration states, I. e., low-frequency swing, the first and the second high frequency vibration. These five states are determined by five critical wind speeds. Through the statistics of more than 70 leaf test results, the probability of each state of leaf and the expected value of each critical wind speed are obtained. The flow showed that vortex shedding occurred in the wake of leaves after they were deformed. The balance measurement shows that the blade resistance coefficient decreases with the increase of Reynolds number and approaches to 0.1. The cantilever beam model was introduced and the blade aerodynamic force was used to calculate the static bending shape of the petiole. The results show that when the wind speed increases gradually from 0 to 5 m / s, the stem bends rapidly downstream, but when the wind speed increases from 5 m / s to 5 m / s, the blade shank bends rapidly when the wind speed increases from 5 m / s to 5 m / s. The bend downstream is slower.
【作者单位】：中国计量大学流体检测与仿真研究所;
【基金】：国家自然科学基金资助项目(11172286)
【分类号】：O355

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