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題名 | Simulation of Moisture Movement with Infiltration Boundary Condition=入滲邊界之土壤水分移動模擬 |
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作者 | 葉一隆; 陳庭堅; 王裕民; Yeh, Yi-lung; Chen, Ting-chien; Wang, Yu-ming; |
期刊 | 國立屏東科技大學學報 |
出版日期 | 20010300 |
卷期 | 10:1 2001.03[民90.03] |
頁次 | 頁35-47 |
分類號 | 434.222 |
語文 | eng |
關鍵詞 | 入滲模式; 二步驟隱式有限插分法; Richards方程式; Infiltration model; Two-step implicit finite difference method; Richards equation; |
中文摘要 | 入滲為五份自地表進入土壤的一種行為,也是描述土壤水份移動的邊界條件,因此,土壤水份入滲模式之正確選用將影響土壤水份傳輸之正確模擬。本文自水田取得土壤後,利用直徑19cm,高120cm之壓克力管進行一維入滲實驗,並探討連續蓄水對入深度之影響,並以Kostiabov,修正Kostiakov,Philip,及修正Philip入滲模式來建立模式,以作為水份於非飽首土壤移動之邊界條件,並利用二步驟隱式有限插分法建立數值模式,來模擬不同入滲模式之邊界條件對連續蓄水之水份移動差異,並模擬分段蓄水之土柱水份變化。 由實驗結果得知,在連續蓄水時,因土壤漸漸飽和,使得同一時間之第二階段累積入滲深度較第一階段為小。而四種套配模式所得結果以Philip入滲模式之誤差值最小,以修正Philip入滲模式之誤差值為最大。由數值模樣當果得知以四種套配模式為邊界條件所得之壓力水頭與以觀測之入滲率為邊界條件所得之壓力水差比以修正Philip入滲模式之誤差值最小,而其他三種入滲模式之誤差值為較大,而且結果亦接近。在分段蓄水程,當地表無蓄水時,因蒸發作用而使地表附近之土壤水皆向上移動,但濕潤鋒仍向下移動,水份向上或向下移動之分界點依蒸發量大小而定,當蒸發量大特,則此分異點將向下移。 |
英文摘要 | Infiltration is the process that percolates water through soil medium. The process also describes the boundary conditions under which moisture moves in the soil medium. Therefore, a precis water infiltration model must be selected to predict the accurate movement of moisture soil. The infiltration rate influences the period and the volume of irrigation; therefore, and accurate infiltration model is a proper tool for agricultural water management . This study analyzed soil samples from a paddy field. One-dimensional infiltration experiments were run with an acrylic pipe 19-cm in ID and 120 cm in length. We investigated the effect of infiltration depth with continuous water ponding on the column surface. The infiltration models that explain the boundary condition of water movement in unsaturated soil medium were established with the experimental results and four infiltration: Kostiakov, modified Kostiakov, Philip, and modified Philip. The numerical model was programmed by a two-step implicit finite difference method. These infiltration models were used as upper boundaries to investigate the difference in moisture movement with continuous ponding. In addition, the change in m moisture inside the soil column was simulated with intermittent ponding. For continuous ponding, the experimental results showed that the accumulated depth in second stage was less than the first stage because the soil was gradually saturated. When comparing experimental results, the smallest infiltration depth difference was shown with the Philip infiltration model and the largest difference was shown with the modified Philip model. When we compared the pressure head differences, both with the boundary condition of the observed infiltration rate and the boundary conditions with the four infiltration models, the modified Philip model showed the smallest error. The other three models showed greater errors and their results were almost identical. During the process of intermittent water ponding, the moisture around the soil surface moved up due to evaporation at the ponding. However, the wetting front inside the soil column still moved downward. The direction was depended on the rate of evaporation. With a higher evaporation rate, the wetting front was deeper than with less evaporation. |
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