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Thermo-Hydro-Mechanical Modeling of Fractured Porous Media with phase Change

Amini, Danial | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52827 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khoei, Amir Reza
  7. Abstract:
  8. The main goal of the research is to formulate and implement the governing equations of Thermo-Hydro-Mechanical (THM) phenomena in fractured/fracturing unsaturated porous media with two-phase fluid flow using the Extended Finite Element Method (XFEM)with phase change consideration(evaporation/condensation). The medium is assumed to be isotropic, and the fluid phases are liquid water, vapor and dry air. The four governing equations are linear momentum equilibrium of the media, continuity equation of water (liquid water and vapor), continuity equation of dry air, and the thermal equilibrium of the medium which are considered to be fully coupled. The fracture is modeled in mode I with exploiting a softening cohesive crack model. In order to consider discontinuities, XFEM is implemented which allows for consideration of the fracture path independent of the mesh. The main task is to extend the previous THM equations by considering the effect of phase change under temperature gradient which causes many additional terms in all of the equations, especially thermal equilibrium equation, to consider evaporation and condensation of water/vapor and the flux of vapor that can go through the surrounding porous media when the fluid in the fracture is heated. In addition, in order to take dry air and vapor as miscible fluids, ideal gas law implemented. In thermal equation, heat transfer through conduction, convection and latent heat is taken into account. Nuclear waste disposal, high-performance concrete subjected to fire, drying procedure of concrete and energy extraction from enhanced geothermal reservoir are the main applications of the proposed numerical model. The results reveal the effect of crack in heat transferring by conduction and convection and importance of crack position in unsaturated media with the flow of vapor. Furthermore, the effect of phase change during drying concrete and subgrade analysis without fracture demonstrate the robustness of the proposed model
  9. Keywords:
  10. Unsaturated Porous Media ; Fracture ; Extended Finite Element Method ; Crack ; Thermo Hydromechanical Analysis ; Phase Changing Methods

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