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題 名 | Micrometeorological Layer/Surface Distribution of Airborne Particles over a Crop Field=作物農地微氣象層氣懸顆粒分佈 |
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作 者 | 廖中明; | 書刊名 | 農業工程學報 |
卷 期 | 39:2 1993.06[民82.06] |
頁 次 | 頁29-43 |
分類號 | 430.1637 |
關鍵詞 | 分佈; 作物; 氣懸顆粒; 微氣象層; 農地; 傳輸與沈澱模式; 隨機步行模式; 紊流; 植物葉覆; Airborne particle; Transport and deposition; Random walk model; Turbulence; Plant Canopy; |
語 文 | 英文(English) |
中文摘要 | 本文目的為描述作物農地紊流結構及以馬可夫鏈為主之新隨機步行模式以提供一傳輸入模式預測農地微氣象層氣懸顆粒分佈。新隨機步行模式考慮對非均質紊流,非零梯度垂直速度之標準偏差,及垂直方向紊流速度之動差偏態作用。文中並討論該模式與其他隨機步行模式比較情形。模式模擬結果顯示紊流速度之動差偏態不僅彌補由非均質垂直速度標準偏差造成之漂移速度具彌補程度大而使得作物葉覆區內顆粒沈澱過程顯著。經由質量守恆測試之模式鑑定顯示第一階馬可夫鏈加水平及垂直方向紊流速度之相關性之隨機步行模式為最佳。最後便利用第一階馬可夫鏈加紊流速度相關性為主之隨機步行模式描述一考慮大氣穩定狀況及紊流之傳輸與沈澱模式。選擇一相關大豆田中噴灑水滴顆粒傳輸之文獻實例以驗證本傳輸與沈澱模式。由研究文獻所得之量測資料與模式預測之顆粒濃度分佈比較結果顯示本模式可合理地預測植物葉覆上及內層之顆粒分佈。 |
英文摘要 | In order to describe a transport model to predict micrometeorological layer/surface airborne particle distributions over agricultural fields, the turbulent structure in a crop field was modeled and a new Random Walk models in terms of a Markov chain concept was presented. A new Random Walk model considers inhomogeneous turbulent flow with non-zero gradient of standard deviation of vertical velocity and skewness of turbulent velocity in the vertical direction was developed and compared to other Random Walk models. Simulation results show skewness of turbulent velocity not only compensates for the drift velocity caused by inhomogeneous of standard deviation of vertical velocity, but the magnitude of compensation is so large that it results in the significance of particle deposition process in the canopy region. Model verification via a mass conservation test shows the first-order Markow chain with turbulent velocity correlation between horizontal and vertical directions works best. A transport and deposition model which considers atmospheric stability conditions and turbulence of airflow was presented using the first-order Markov chain with turbulent velocity correlation. A model case obtained from research literature regarding to the spray droplet transport in a soybean field was chosen to verify the transport and deposition model. Comparison between measured data from research literature and predicted concentration distributions from model show reasonable prediction of particle distributions above and within a plant canopy. |
本系統中英文摘要資訊取自各篇刊載內容。