Numerical Methods in Soil Hydrology: TDR Waveform Analysis and Water Vapor Diode Simulation Zhuangji Wang Iowa State University
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Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2017 Numerical methods in soil hydrology: TDR waveform analysis and water vapor diode simulation Zhuangji Wang Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Soil Science Commons Recommended Citation Wang, Zhuangji, "Numerical methods in soil hydrology: TDR waveform analysis and water vapor diode simulation" (2017). Graduate Theses and Dissertations. 15636. https://lib.dr.iastate.edu/etd/15636 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Numerical methods in soil hydrology: TDR waveform analysis and water vapor diode simulation by Zhuangji Wang A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Soil Science (Soil Physics) Program of Study Committee: Robert Horton, Major Professor Daniel Attinger Dan B. Jaynes James Rossmanith Tom Sauer Iowa State University Ames, Iowa 2017 Copyright © Zhuangji Wang, 2017. All rights reserved. ii DEDICATION For My parents, Zhaokuan Wang and Yuye Hu iii TABLE OF CONTENTS DEDICATION .......................................................................................................................... ii ABSTRACT .............................................................................................................................. v CHAPTER 1. GENERAL INTRODUCTION ......................................................................... 1 Soil Water Content and Time Domain Reflectometry .............................................................. 1 Soil Heat and Water Movement and Water Vapor Diode ........................................................ 6 Objectives ................................................................................................................................. 7 Organization of the Thesis ........................................................................................................ 8 References ................................................................................................................................. 8 CHAPTER 2. TANGENT LINE / SECOND ORDER BOUNDED MEAN OSCILLATION WAVEFORM ANALYSIS FOR SHORT TDR PROBE ..................... 11 Abstract ................................................................................................................................... 11 Abbreviation ........................................................................................................................... 12 Introduction ............................................................................................................................. 12 Algorithms .............................................................................................................................. 14 Materials and Methods ............................................................................................................ 17 Results and Discussion ........................................................................................................... 18 Summary ................................................................................................................................. 23 Acknowledgements ................................................................................................................. 24 References ............................................................................................................................... 24 Appendix ................................................................................................................................. 25 CHAPTER 3. A COMPARISON OF SECOND ORDER DERIVATIVE BASED MODELS FOR TIME DOMAIN REFLECTOMETRY WAVEFORM ANALYSIS ..... 27 Abstract ................................................................................................................................... 27 Abbreviation ........................................................................................................................... 28 Introduction ............................................................................................................................. 28 Theory ..................................................................................................................................... 31 Materials and Methods ............................................................................................................ 35 Results and Discussion ........................................................................................................... 37 Conclusions ............................................................................................................................. 45 Acknowledgements ................................................................................................................. 45 References ............................................................................................................................... 45 CHAPTER 4. THE IMPACT OF WATER VAPOR DIODES ON SOIL WATER REDISTRIBUTION ......................................................................................................... 48 Abstract ................................................................................................................................... 48 Abbreviation ........................................................................................................................... 49 Introduction ............................................................................................................................. 49 Theory ..................................................................................................................................... 50 Materials and Methods ............................................................................................................ 54 Results and Discussion ........................................................................................................... 58 Summary ................................................................................................................................. 63 Acknowledgements ................................................................................................................. 64 iv References ............................................................................................................................... 64 Appendix A ............................................................................................................................. 66 Appendix B ............................................................................................................................. 69 CHAPTER 5. A TWO-DIMENSIONAL SIMULATION OF WATER VAPOR DIODES .. 71 Abstract ................................................................................................................................... 71 Abbreviation ........................................................................................................................... 72 Introduction ............................................................................................................................. 72 Materials and Methods ............................................................................................................ 73 Results and Discussion ........................................................................................................... 80 Summary ................................................................................................................................. 83 Acknowledgements ................................................................................................................. 84 References ............................................................................................................................... 84 CHAPTER 6. GENERAL CONCLUSIONS .......................................................................... 87 APPENDIX: NUMERICAL SCHEMES FOR CHAPTER 4 AND CHAPTER 5................. 88 Numerical Scheme for Chapter 4 ............................................................................................ 88 Numerical Scheme for Chapter 5 ............................................................................................ 89 ACKNOWLEGEMENTS ....................................................................................................... 91 v ABSTRACT Soil water content impacts all soil physical, chemical and biological properties. Soil water movement in shallow soil layers has critical importance for plant water use, foundation stability, energy transfer and chemical diffusion. Numerical analysis is one way to study soil water. New numerical methods are presented in this thesis to determine soil water content from time domain reflectometry (TDR) measurements and simulate soil water accumulation in selected soil layers. TDR enables nondestructive and continuous soil water content measurements. Traditional TDR waveguides have relatively long probes (>150 mm), but new TDR waveguides tend to use short probes (<40 mm) to enable the measurements of water content near