A Study of Soil Moisture Hysteresis Effect in Unsaturated Soil
Date Issued
2004
Date
2004
Author(s)
Huang, Han-Chen
DOI
zh-TW
Abstract
研究依據van Genuchten（1980）之土壤保水曲線關係式發展一可適用於遲滯現象之土壤水分遲滯模式，在已知土壤主要乾燥曲線及主要濕潤曲線之參數下，推衍出任一乾燥或濕潤狀態之土壤水分遲滯曲線；模式係以前人研究之實驗數據及本研究進行之實驗數據進行準確性分析，並與Scott model及KP model進行比較，結果顯示本研究所發展之土壤水分遲滯模式具備簡易、準確及方便等優點，並且能避免相關模式未能處理之汲取效應（Pumping effect）。
研究並將所發展之土壤水分遲滯模式納入土壤水分滲流數值模式中，進行土壤水分與張力混合型控制方程式、張力型控制方程式之數值解析質量平衡分析，結果顯示土壤水分與張力混合型控制方程式之數值模式具備較佳之質量平衡；另數值模式與Gillham（1979）之實驗結果進行比較，結果顯示數值模擬結果與實驗結果相近，代表遲滯效應是土壤水分滲流研究中應予考量之重要因子；最後研究並進行三種不同土壤之水分滲流模擬以進一步探討遲滯現象之特性。
This study present a novel hysteresis model based on van Genuchten’s soil-moisture relationships. The proposed model yields series closed form relationships in which two shape factors and are determined from the main drying and wetting curves. Experiments and literature-cited data were used to assess model accuracy. The proposed model was also compared with the Scott and KP models. Analytical results indicate that the present model is simple, accurate and effective in constructing the series wetting and drying scanning curves. Notably, the proposed model outperforms the Scott and KP models in terms of model accuracy. Moreover, the novel model eliminates the pumping effect and has perfect closure at scanning curve reversal points.
There are two numerical schemes adopted to this research: finite difference method and finite element method. These models combined present hysteresis model to estimate scanning curves. In the research, there are two different forms of Richards equation: h-based and mix form. The results showed that the mix-form of Richards equation has had better mass balance; therefore, the simulation is based on the mix-form of Richards equation. Importance of hysteresis is based on that the numerical scheme is verified by the Gillham’s (1979) experimental data. Finally, three numerical schemes are adopted to three case studies to analyze hysteretic phenomena. The results of numerical analysis are helpful to understand the insight physical behavior of hysteresis.
Subjects
汲取效應
遲滯效應
數值模式
Pumping effect
Hysteresis effect
Numerical schemes
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-93-D88622005-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):b54f9a8700fb181f63176ae99eb70aea