利用孔頸系集模型推估濕潤相流體特徵曲線掃瞄迴圈之研究

Deriving Wetting Phase Fluid Hydraulic Conductivity Scanning Loops Using Unit-Pore-Throat Ensemble Model Framework

蘇威名(Wei-Ming Su)

指導教授 ： 李天浩

國立臺灣大學/工學院/土木工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.02536

摘要

繼鄭安孺(2004)、馮智勇(2006)等由土壤水－空氣毛細壓力與飽合度關係掃描曲線，透過孔頸單元系集模型，推估水與微溶性非水相液體（Non-Aqueous Phase Liquid, NAPL）在相同土壤中的毛細壓力與飽合度關係掃描曲線，以及毛細壓力與水的傳導係數關係曲線之研究方向。本研究的目標，除了增加孔頸單元組數，以達到「系集」目標外，另外，從模擬案例中找尋孔頸單元毛細壓力和水力傳導係數的簡化規則，以期能更有效率的達到推估目標。

研究方法是以鄭安孺(2004)利用實驗真實土壤保水曲線，反演導出水力等價的孔頸單元系集模型，使用Surface Evolver軟體在不同毛細壓力下，導出在每個孔頸單元中水－NAPL的界面位置和兩液相飽和度；再以計算流體動力學軟體CFDRC計算孔頸單元的相對傳導度；最後，統計整合所有孔頸單元的模擬結果，估計該土壤的水－NAPL特徵曲線( Curve)。

除了以上主要目標外，本研究在模擬流程中解決以下三項問題：
1. 為了節省計算資源、保留孔單元計算結果，未來針對不同的土壤可以結合不同的管長因子，透過測試決定孔單元合適的基本管長，並且證實基本管長孔單元和管單元水力傳導數的組合，和完整管長孔單元計算結果一致。
2. 透過比較不同孔頸單元相對水力傳導係數的模擬結果，找出能簡化代表各孔頸單元在臨界毛細壓力時，相對水力傳導係數和管徑尺寸關係的規則。並利用此規則內插推估其他尺寸，未實際計算的孔頸單元相對水力傳導係數。
3. 利用上項規則，可以減少計算需求，以較有效率的方式，增加孔頸單元分佈樣本，改善系集模型因為有限孔頸單元，造成 關係曲線在某些地方曲折較大問題，得到較細緻化的曲線。

關鍵字

特徵曲線 ； 孔頸單元 ； 掃瞄迴圈 ； 孔頸系集模型

並列摘要

Abstract

Following the research of Jheng(2004)and Fong(2006), based on Unit-Pore-Throat Ensemble Model (UPTEM), using the water-air soil retention curve( Curve), to estimate the relationship of “capillary pressure-saturation”( ) and “capillary pressure-permeability”( ) caused by water and Non-Aqueous Phase Liquid(NAPL) in the same soil. One objective of this research is reaching whole ensemble curve by increasing the number of UPT. The other objective is estimating curve more efficiently by finding a simple rule to get the relationship of capillary pressure and hydraulic conductivity.

Main method is like Jheng(2004) establishing a hydraulic equivalent unit-pore-throat ensemble model by using experimental retention curve. Using the software － Surface Evolver to find water-NAPL interface and saturation of all pore-throat units in different capillary pressure. And then calculate the hydraulic conductance of pore-throat unit by hydraulic kinetics calculating software － CFDRC. At last, integrate the simulating results of all pore-throat units by statistics and estimate water－NAPL Curve of the soil sample.

There are three problems solved in this research with the above-mentioned procedure：
1. In order to save time, keep the calculating results and combine different length factor in different soil samples, decide the unit length factor by testing. The effect of hydraulic conductance when length factor changes is provided that the result and relative conductance value calculated from original pore-throat unit are the same.
2. A simple rule to get the relationship between hydraulic conductance and throat size in different critical capillary pressure is found out by comparing the simulation results of different pore-throat units. So the hydraulic conductance of new inserted pore-throat units can be calculated by using the rule.
3. By using the simple rule, more hydraulic conductance can be calculated more easily and more efficiently. So the curve can be refined by inserting more pore-throat units.

並列關鍵字

scanning loop ； pore-throat unit ； unit-pore-throat emsemble model

參考文獻

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