Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Numerical Study of Thermo-hydraulic Boundary Condition for Surface Energy Balance

지표면 열평형의 열-수리적 경계조건에 대한 수치해석

  • Shin, Hosung (Dept. of Civil & Environmental Engrg., Univ. of Ulsan) ;
  • Jeoung, Jae-Hyeung (Dept. of Geotechnical Engrg. Research, Korea Institute of Civil Engrg. and Building Technology)
  • 신호성 (울산대학교 건설환경공학부) ;
  • 정재형 (한국건설기술연구원 지반연구본부)
  • Received : 2021.11.05
  • Accepted : 2021.11.24
  • Published : 2021.12.31
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Abstract

Boundary conditions for thermal-hydraulic problems of soils play an essential role in the numerical accuracy. This study presents a boundary condition considering the thermo-hydraulic interaction between the ground and the atmosphere. Ground surface energy balance consists of solar radiation, ground radiation, wind convection, latent heat from water evaporation, and heat conduction to the ground. Equations for each heat flux are presented, and numerical analyses are performed in conjunction with the FEM program for the thermal-hydraulic phenomenon of unsaturated soils. Numerical results using the weather data at the Ulsan Meteorological Observatory are similar to the measured surface temperature. Latent heat caused by water evaporation during the daytime lowers the surface temperature of the bare soil, and a thermal equilibrium is reached at nighttime when the effect of the ground condition is significantly reduced. The temperature change of the surface ground is diminished at the deeper ground due to its thermal diffusion. Numerical analysis where the surface ground temperature is the primary concern requires considering the thermo-hydraulic interaction between the ground and the atmosphere.

지반의 열-수리 현상에 대한 수치해석에서 경계조건은 해석결과의 정확도에 중요한 역할을 한다. 본 연구에서는 지반과 대기의 상호작용을 고려한 열-수리 경계조건을 제시하였다. 지면의 에너지 평형은 태양복사, 지구복사, 바람에 의한 대류, 수분 증발에 대한 잠열 그리고 지중으로의 열전도로 구성된다. 각각의 열흐름에 대한 방정식을 제시하고, 불포화 지반의 열-수리 현상에 대한 해석프로그램과 연계하여 수치해석을 수행하였다. 울산기상대에서 관측된 기상데이터를 이용한 수리-열적 해석에서 실측된 지표면 온도와 수치해석 결과가 매우 유사하였다. 낮시간의 수분 증발에 의한 잠재열은 비포장 지면의 온도를 낮추며, 야간시간에는 지면조건의 영향이 감소한 열적평형 상태에 도달하였다. 지면의 온도변화는 지중으로 깊어질수록 열확산으로 감소하였다. 지표면의 온도가 주요 관심사인 수치해석에서는 지반과 대기의 열-수리적 상호작용을 고려한 수치해석을 수행해야 한다.

Keywords

Acknowledgement

본 연구는 한국연구재단 개인연구지원사업(NRF-2019R1A2C200441913)과 한국건설기술연구원의 "지하매설 압력관의 실시간 건전성 진단 및 관리 기술 개발" 연구의 지원으로 수행되었으며, 이에 깊은 감사를 드립니다.

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