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Studies on the mechanism of 'honami' (plant waving) generation and the exchange processes of matter and energy caused by it, considering a large deflection of plant stalk.

研究“honami”（植物波动）产生机制及其引起的物质和能量交换过程，考虑植物茎的大偏转。

基本信息

批准号：
10650513
负责人：
HINO Mikio
金额：
$ 2.24万
依托单位：
Chuo University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Aims: 'Honami' (plant waving) is a well-known phenomenon observed in paddy and wheat fields, The phenomenon is interesting not only from the view point of fluid mechanics but also from a practical view of environment and food production, since the plant waving may contribute considerably to accelerate the exchange of matter (COィイD22ィエD2 and OィイD22ィエD2), heat and energy. In order to shed a light on the phenomenon of 'honami', a three dimensional numerical simulation considering large deflection of plant stalk has been performed.Means: Three-Dimensional turbulent flow above and within a canopy layer has been computed numerically applying LES turbulence model of Kanda and Hino (1994). The waving oscillation of plant stalk has been simulated by rows of elastic cylinders.Results: At the initial stage of turbulent canopy flow development, a street of periodic longitudinal vortices has been generated caused by the inflectional point flow instability mechanism. At the initial stage, the correlation between the periodicity of vortex and the frequency of plant oscillation is low. As time steps go on, the periodicity of longitudinal vortices gradually changes and becomes a little irregular, and the periodicity approaches to the natural frequency of plant stalk oscillation.Within a limited range of this simulation, the results seem to support the gust-attack and/or resonance theory of 'honami' generation, although the conclusion does not exclude the possibility of other mechanisms.

目的：‘Honami’(植物挥动)是在稻田和小麦田里观察到的一种众所周知的现象，这种现象不仅从流体力学的角度来看很有趣，而且从环境和食物生产的实际角度来看也很有趣，因为植物挥舞可能会大大加速物质(COィイD22ィエD2和OィイD22ィエD2)、热量和能量的交换。为了揭示“Honami”现象，考虑植物茎的大挠度，进行了三维数值模拟。同时：采用Kanda和Hino(1994)的LES湍流模型对冠层上方和内部的三维湍流流动进行了数值模拟。结果：在冠层湍流发展的初始阶段，由于拐点流不稳定性机制，产生了一条周期性的纵向涡街。在初始阶段，涡旋周期与植物振荡频率的相关性较低。随着时间的推移，纵向涡旋的周期性逐渐变化并变得有点不规则，并且周期性接近植物茎振荡的固有频率。在有限的模拟范围内，结果似乎支持阵风攻击和/或共振产生的理论，尽管结论不排除其他机制的可能性。