Dissipative particle dynamics with attractive and repulsive particle-particle interactions

In molecular dynamics simulations, a combination of short-range repulsive and long-range attractive interactions allows the behavior of gases, liquids, solids, and multiphase systems to be simulated. We demonstrate that dissipative particle dynamics (DPD) simulations with similar pairwise particle-particle interactions can also be used to simulate the dynamics of multiphase fluids. In these simulations, the positive, short-range, repulsive part of the interaction potentials were represented by polynomial spline functions such as those used as smoothing functions in smoothed particle hydrodynamics, and the negative long-range part of the interaction has the same form but a different range and amplitude. If a single spline function corresponding to a purely repulsive interaction is used, the DPD fluid is a gas, and we show that the Poiseuille flow of this gas can be described accurately by the Navier-Stokes equation at low Reynolds numbers. In a two-component system in which the purely repulsive interactions between different components are substantially larger than the purely repulsive intracomponent interactions, separation into two gas phases occurs, in agreement with results obtained using DPD simulations with standard repulsive particle-particle interactions. Finally, we show that a combination of short-range repulsive interactions and long-range attractive interactions can be used to simulate the behavior of liquid drops surrounded by a gas. Similar models can be used to simulate a wide range of processes such as multiphase fluid flow through fractures and porous media with complex geometries and wetting behaviors.