A novel DEM-based coupled 3D thermo-hydro-mechanical mesoscopic model for cracked porous materials

Most of the physical phenomena in engineering problems occur under non-isothermal conditions.The occurrence of some physical phenomena or chemical reactions can lead to local temperature changes and, consequently, to heat transfer and even local phase changes in the fluid.The need to consider the effect of heat transfer and phase changes in the fluid becomes critical in analyses of many multi-field problems in porous and fractured materials.A novel DEM-based porescale 3D thermo-hydro-mechanical (THM) model of two-phase fluid flow and heat transfer in fluid and solids is based on a direct numerical simulation approach.The model's original concept is based on the notion that in a physical system, two domains coexist: the 3D discrete (solid) domain and the 3D continuous (fluid) domain.Both domains are discretized into a coarse mesh of tetrahedra.The THM model was validated by comparing the numerical results with the analytical solution of the classic 1D heat transfer problem.Numerical calculations were carried out for bonded granular specimens imitating concrete with a 3D DEM fully coupled with 3D CFD (based on a fluid flow network) and 3D heat transfer that linked discrete mechanics with fluid mechanics and heat transfer at the meso-scale.The heat transfer was related to the fluid (diffusion and advection) and bonded particles (conduction).Bonded particle assemblies with random grain distribution were considered.Perfect accordance was obtained between numerical and analytical outcomes.In addition, the effects of a macro-crack in the specimen on the distribution of fluid pressure, density, velocity, and temperature were studied.