Korean Journal of Soil Science and Fertilizer (한국토양비료학회지)

Korean Society of Soil Science and Fertilizer (한국토양비료학회)
권호 표지

Finite Difference Model of Unsaturated Soil Water Flow Using Chebyshev Polynomials of Soil Hydraulic Functions and Chromatographic Displacement of Rainfall

Chebyshev 다항식에 의한 토양수분특성 및 불포화 수리전도도 추정과 부분 치환 원리에 의한 강우 분포를 이용한 토양수분 불포화 이동 유한차분 수리모형

  • Ro, Hee-Myong (School of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University) ;
  • Yoo, Sun-Ho (School of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University) ;
  • Han, Kyung-Hwa (School of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University) ;
  • Lee, Seung-Heon (Rural Research Institute, Korea Agricultural and Rural Infrastructure Corporation) ;
  • Lee, Goon-Taek (National Instrumentation Center for Environmental Management, Seoul National University) ;
  • Yun, Seok-In (School of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University) ;
  • Noh, Young-Dong (School of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University)
  • 노희명 (서울대학교 농생명공학부) ;
  • 유순호 (서울대학교 농생명공학부) ;
  • 한경화 (서울대학교 농생명공학부) ;
  • 이승헌 (농업기반공사 농어촌연구원) ;
  • 이군택 (서울대학교 농업과학공동기기센터) ;
  • 윤석인 (서울대학교 농생명공학부) ;
  • 노영동 (서울대학교 농생명공학부)
  • Received : 2003.07.08
  • Accepted : 2003.07.25
  • Published : 2003.08.30
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Abstract

We developed a mathematical simulation model to portray the vertical distribution of soil water from the measured weather data and the known soil hydraulic properties, and then compared simulation results with the periodically measured soil water profiles obtained on Jungdong sandy loam to verify the model, In this model, we solved potential-based Richards' equation by the implicit finite difference method superimposed on the predictor-corrector scheme. We presumed that: soil hydraulic properties are homogeneous; soil water flows isothermally; hysteresis is not considered; no vapor flows; no heat transfers into the soil profiles; and water added to soil surface is distributed along the soil profile following partial displacement principle. The input data were broadly classified into two groups: (1) daily weather data such as rainfall, maximum and minimum air temperatures, relative humidity and solar radiation and (2) soil hydraulic data to approximate unsaturated hydraulic conductivity and water retention. Each hydraulic polynomial function approximated using the Chebyshev polynomial and least square difference technique in tandem showed a fairly good fit of the given set of data. Vertical distribution of soil water as approximations to the Richards' equation subject to changing surface and phreatic boundaries was solved numerically during 53 days with a comparatively large time increment, and this pattern agreed well with field neutron scattering data, except for the surface 0.1 m slab.

기상 자료와 토양 수리 특성을 입력하여 토양수분의 수직 이동 및 분포를 예측할 수 있는 수치모형을 개발하고, 이 모형을 검정하기 위해 중동사양토를 대상으로 추정한 결과와 중성자 산란법에 의해 측정한 수분단면을 비교하였다. 이 모형에서 토양수분 포텐셜을 기준으로 한 Richards 방정식의 해를 predictor-corrector 격자에 투영한 음함수 유한차분법에 의해 구하였다. 이 모형에서는 토양단면의 수리특성은 균질하고, 토양수분은 등온적으로 흐르고, 수분이력현상은 고려하지 않고, 수증기 및 열 이동은 일어나지 않고, 빗물은 토양 단면에 부분 치환원리에 의해 분배된다고 가정하였다. 이 모형의 입력 자료는 크게 강우량, 최고 및 최저 기온, 상대습도 및 일사량의 일일 기상자료와 불포화 수리전도도 및 수분보유 특성 함수를 추정하기 위한 토양 수리 자료로 구분하였다. Chebyshev 다항식과 최소 자승차를 이용하여 추정한 토양 수리 다항식은 입력 자료와 매우 잘 일치하였다. 다양한 지표 및 하부 경계조건에서 53일 동안 상대적으로 시간증가분을 크게 하여 추정한 Richards 방정식의 해인 토양수분 수직 단면은 지표 10 cm를 제외하고는 중성자 산란법에 의해 측정한 결과와 잘 일치하였다.

Keywords

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