https://scholars.lib.ntu.edu.tw/handle/123456789/169140
標題: | 反演孔頸網絡模型參數、建構導水曲線與發展動態二相流傳輸之研究(2/2) A Study on Parameter Identification of Pore-Throat Network Model, Derivation of Conductivity Curve and on the Two-Phase Flow within the Dynamic Regime |
作者: | 李天浩 | 關鍵字: | 孔隙介質;非水相性液體;二相流;特徵曲線;磁滯現象;非濕潤相殘餘量;單元孔頸系集模型;置換機制;逆向問題;Porous medium;non-aqueous phase liquid (NAPL);two phase flow;characteristic curves;hysteresis;non-wetting phase residuals;Unit-pore-throat Ensemble Model;displacement mechanism;inverse problem | 公開日期: | 2004 | 出版社: | 臺北市:國立臺灣大學土木工程學系暨研究所 | 摘要: | 本研究原先的構想是引入「孔頸網絡 模型」(pore-throat network model)的觀念, 完成發展孔頸網絡模型之非實驗性建構技 術以及建制一套較完整的動態傳輸模擬程 序的工作。唯本研究在深入探討「孔頸網 絡模型」現有應用理論的完整性後,發現 因為「孔頸網絡模型」有尺度效應的問題, 無法完成解決逆向問題的研究目標,因此 乃變更第二年的研究目標,改為發展一全 新的孔隙尺度微模型,稱之為「單元孔頸 系集模型」(Unit-pore-throat Ensemble Model)。 1 「單元孔頸系集模型」在幾何型態 上,具有與孔頸網絡模型類似的擴張與收 縮的「孔─頸」結構;三角形頸管與正立 方體頂角銜接的簡單幾何形狀,使得角隅 濕潤相能夠相互連結,有利於未來計算單 元孔頸傳導度。在力學機制上,「單元孔 頸系集模型」是完全由微觀流體界面力學 平衡原理,計算在某特定毛細壓力下,二 流體相界面的形狀、位置、飽和度,以及 流體界面幾何形狀與飽和度達到臨界狀 態,發生置換的門檻毛細壓力條件。在正 向分析上,「單元孔頸系集模型」可以模 擬微觀墨水瓶效應與汲取過程中非濕潤相 的入陷,實現巨觀上的磁滯現象,同時可 以表現不同接觸角對於毛細壓力─飽和度 曲線的影響。在逆向演算時,「單元」和 「系集」的設計,避免網絡模型的尺寸效 應和聯合機率密度問題,孔頸大小分布參 數和退水、進水毛細壓力─飽和度曲線的 連結關係較為直接。 利用退水和進水曲線的試驗資料,嘗 試不同的「頸管管徑」-「孔徑徑比值」 兩變數的聯合機率密度函數,歸納得兩變 數為一對一對應分布即可得到良好的擬合 結果的結論。正向演算證實本微模型基於 幾何模型和物理原理,確實具有實現巨觀 上磁滯現象以及表現不同接觸角對於毛細 壓力─飽和度影響的能力。唯本模型無論 在正向或逆向演算上均非常繁複,並且目 前反演模型參數的理論仍是基於過度簡化 的假設上,雖然可以得到容易解析的好 處,但是也限制模式的表現和解釋能力, 還待未來研究逐步改進。 This study establishes a Unit-Pore- Throat Ensemble Model (UPTEM). It mimics the soil pore structure by many pore-throat units of different sizes which are not connecting to one another. Methodologies are developed to estimate the parameters of size distributions of pores and throats. They utilize the water-air soil experiment data of capillary pressure (Pc) and saturation (s) during primary drainage, primary imbibition and secondary drainage processes. The objective is to make the UPTEM hydraulically equivalent to the actual water-air-soil system. Provided with the UPTEM parameters, the Pc-s scanning loops of water-NAPL two-phase fluids within the same soil can be inferred without doing the characteristic-curve experiments. The equilateral triangle throats and cubic pore morphology of pore-throat units enable the UPTEM to simulate the ink-bottle effect. The simple geometry and interconnected pore-throat edges make easy the positioning of fluid-interface balanced with the capillary pressure using Laplace Equation, as well as calculating the critical position and capillary pressure for interface displacement. Knowing the interface position, conductivity in addition to wetting- and non-wetting- phase saturations can be computed. In direct problems, UPTEM can reproduce the hysteresis effect and quantify the trapping ratio on macro-scale. For the displacement criteria are derived from fluid mechanic principles and morphology of pore-throat units, UPTEM can demonstrate the effect of contact angle on characteristic curves explicitly. The ensemble design of pore-throat units avoids the difficulties caused by size effect and the need to estimate joint distribution of network pore-throats in inverse problems. For the same reason, the size distribution parameters are more directly linked to the Pc-s curves. Fitting the drainage and imbibition Pc-s curves with UPTEM was tried with application of different ‘throat’ and ‘aspect ratio’ distribution types. It is shown that using a simple one-to-one relationship between the two variables, the model can match the data reasonably well. The drawbacks of the UPTEM model are tedious calculation and over-simplified parameter estimation methodologies. Future research is needed for further improvement. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/2857 | 其他識別: | 922211E002083 | Rights: | 國立臺灣大學土木工程學系暨研究所 |
顯示於: | 土木工程學系 |
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