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.

点击翻译按钮获取中文摘要

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.