著者
林 陽生
出版者
日本農業気象学会
雑誌
農業気象 (ISSN:00218588)
巻号頁・発行日
vol.48, no.1, pp.57-64, 1992-06-10 (Released:2010-02-25)
参考文献数
15

To investigate dependencies in the magnitudes of a waving ear on mean wind speed, field observations were carried out over a barley filed in the ripe stage. Fluctuating displacements derived from HONAMI were measured using a newly designed 2-dimension strain sensor. The velocity fields were measured by a sonic anemometer-thermometer.A coherently waving phenomena of HONAMI appeared and was evaluated by the fluctuating displacements of a single ear of the stand. Dividing a time series of the fluctuating displacement into five typical bands of frequency by use of an analog filter, it was shown that there are two dominants of 0.5-Hz and below 0.1-Hz in the original. The bands were from a natural frequency and a gustness of wind respectively. Comparing the amplitudes, the natural frequency contributed remakably to the original fluctuation of HONAMI.Magnitudes of an instantaneous ear-displacement, which represents 0.5-0.6-Hz of frequency, varied with increments of the mean wind speed within a range of 2.6-4.4-m/s. Except for this range, the dependency between the amplitude and the wind speed was not clear.Instantaneous changes in lateral displacements and velocity fluctuations were quite similar except for the component of higher frequencies. Under such circumstances, an ear-displacement will appear to infulence strongly the aero-dynamical properties of the canopy boundary layer.The force per unit length acts on a waving ear generates by a relative velocity of u-dx/dt. Here, u is the mean wind speed, and dx is the displacement of an ear from its mean position during dt. Using this concept, drug force was evaluated under two criteria for leeward ear-moving and ear-standing. Under the windy conditions, the force loaded on an waving ear reduced by 10% against the standing criterion with dx=0. On the other hand, the reduction rate became small down to 4% of the standing criterion under the condition of weak wind.
著者
三村 信男 江守 正多 安原 一哉 小峯 秀雄 横木 裕宗 桑原 祐史 林 陽生 中川 光弘 太田 寛行 ANCHA Srinivasan 原沢 英夫 高橋 高橋 大野 栄治 伊藤 哲司 信岡 尚道 村上 哲
出版者
茨城大学
雑誌
基盤研究(A)
巻号頁・発行日
2005

気候変動への影響が大きいアジア・太平洋の途上国における適応力の形成について多面的に研究した.ベトナム、タイ、南太平洋の島嶼国では海岸侵食が共通の問題であり、その対策には土地利用対策と合わせた技術的対策が必要である.また、インドネシア、中国(内蒙古、雲南省など)の食料生産では、地域固有の自然資源を生かした持続可能な農業経営・農村改革が必要である.また、本研究を通して各国の研究者との国際的ネットワークが形成されたのも成果である.