Haines jumps and meniscus reconfiguration are commonly observed in immiscible two-phase flows through porous media. The experiment found that the fluid-fluid interface moves rapidly during these two phenomena. This leads to hydraulic change and entropy production events, which have important implications for relative permeability of two-phase flow in porous media. However, owing to the energy-transfer process remains to be elucidated, their impact on transport of heat and mass in porous media has not yet been well predicted. By analyzing the exchange process between surface energy, kinetic energy, and viscous dissipation, this study provides a better understanding of meniscus dynamics and whether these effects are significant on a larger scale. In this study, Direct Numerical Simulation (DNS) combined with level-set method was used to simulate the process of Haines jumps and meniscus reconfiguration. A governing equation combined with density-scale continuum surface force (CSF) model was derived for energy conservation, and simulations were performed considering high-density and high-viscosity ratios. The rate of surface-energy change was evaluated using CSF model. A capillary tube was designed to verify the rate of surface-energy change in simulation. Comparison of simulation and theoretical data indicates that the density-scale CSF model can satisfactorily evaluate the rate of change in surface energy. Besides, to compare energy transfer process in Haines jumps and meniscus reconfiguration, two simulation cases were designed: (I) Haines jump and meniscus reconfiguration occur individually, and (II) Haines jump and meniscus reconfiguration occur simultaneously. We investigated the energy exchange process and compared the effects of the inertial force and viscous dissipation between cases I and II. Based on the simulation results, the interface releases surface free energy to the system during the Haines jumps and meniscus reconfiguration. In the case of only Haines jumps, a portion of the released surface energy is absorbed by another fluid-fluid interface, thus reducing the surface-energy release rate in the system. This energy can be dissipated promptly, resulting in a rapid viscous-dissipation growth; but the kinetic-energy change is negligible. However, when meniscus reconfiguration occurs, released surface energy is difficult to reabsorb and cannot dissipate quickly. Thus, a significant amount of released energy is converted into kinetic energy, which is subsequently damped by the fluid. This significant kinetic-energy oscillation generates a large inertial force and spreads over a wider sphere of influence in the porous media. Energy transfer process shows a more detailed fundamental understanding of mass transfer in porous media, such as flow perturbations, entropy production and permeability in porous media, and it helps a rigorous process for upscaling models used for thermodynamic, heat and mass transfer in porous media.
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