| Dissipative Particle Dynamics (DPD) is a recently developed method for simulating complex fluid flows and other colloidal phenomena. It is a mesoscopic method, in that it does not rely on a continuum-level description of matter, but nor does it completely capture molecular-level detail. In DPD a particle is a fluid packet that consists of a group of molecules, and each particle interacts with the other particles in ways that conserve both mass and momentum. In order to explore its potential as a method for studying suspensions and emulsions, we have used a novel implementation of DPD to calculate a variety of transport properties pertaining to two-phase systems. Fast DPD algorithm is devised to reduce the computational time to O(N) from conventional O( N2). For solid-liquid systems, these properties include the hydraulic permeability of fibrous porous media, and the drag on a sphere at low and moderate Reynolds numbers. Trajectories of a falling cylinder in a two-dimensional channel are calculated in an intermediate inertia regime as well as the rotational speed of circular and elliptical cylinders. We have also shown that, by including two populations of particles in the simulations, and having different levels of soft, repulsive interactions between them, two-phase liquid-liquid systems can be modeled. In particular, calculations of the surface tension and deformation of two- and three-dimensional liquid drops in shear flows show the expected behavior. The behavior of deformation parameter and oscillation in the aspect ratio of DPD drops also yields the correct behavior. Finally, in our liquid-liquid simulations we have constructed model surfactants comprised of two particles, one from each population. These amphiphilic particles reduce the surface tension at liquid-liquid interfaces, providing a basis for mesoscopic simulations of colloidal systems such as solutions of micelles and microemulsions. |
