Dissipative Particle Dynamics (DPD) and the Volume of Fluid (VOF) Simulations of Pore-Scale Multiphase Flow

The application of dissipative particle dynamics (DPD), a relatively new mesoscale method for simulating multiphase flow problems within variably saturated pore spaces is presented here. The complex geometry of porous media consisting of different void and solid obstacle shapes can be conveniently handled by DPD. The conventional DPD method that employs purely repulsive conservative (non-dissipative) particle-particle interactions to simulate the behavior of gases is capable of simulating the saturated flow fields. However, in order to simulate unsaturated multiphase flow through porous media, a conservative particle-particle interaction model that combines both short-range repulsive and long-range attractive interactions was developed to simulate multiphase flow in variably saturated pore spaces. This form of conservative particle-particle interactions allows the behavior of multiphase systems consisting of gases, liquids and solids to be modeled. An alternative grid-based method, the volume of fluid (VOF) method, is also applied to the same problems and compared with the DPD simulation results. Both methods appear to be able to handle complex pore geometries, fluid/fluid/solid contact line dynamics and fluid/fluid interface dynamics such as fragmentation and coalescence. The numerical results clearly demonstrate the potential values of both DPD and VOF methods for simulating complex multiphase flow dynamics in variably saturated pore spaces.