A novel DEM-based pore-scale thermal-hydro-mechanical model for fractured non-saturated porous materials

Abstract

For fracture propagation, a novel DEM-based pore-scale thermal-hydro-mechanical model of two-phase fluid flow with heat transfer in non-saturated porous materials with low porosity was developed. Numerical computations were performed for bonded granular specimens, using a DEM fully coupled with CFD (based on a fluid flow network) and heat transfer, which integrated discrete mechanics with fluid mechanics and heat transfer at the meso-scale. Both the fluid (diffusion and advection) and bonded particles (conduction) were involved in heat transfer. The numerical findings of the coupled thermal-hydraulic-mechanical (THM) model were first compared to the analytical solution of the classic 1D heat transport problem. The numerical and analytical outcomes were in perfect agreement. Advection's impacts on the cooling of a bonded particle assembly were next numerically demonstrated for low and high Peclet numbers. Finally, the THM model's utility was proved in a thermal contraction test employing a bonded particle assembly during cooling, which resulted in the creation of a macro-crack. The effects of a macro-crack on the distribution of fluid pressure, density, velocity, and temperature were studied.