The non-Newtonian behavior of a monodisperse concentrated dispersion ofspherical particles was investigated using a direct numerical simulationmethod, that takes into account hydrodynamic interactions and thermalfluctuations accurately. Simulations were performed under steady shear flowwith periodic boundary conditions in the three directions. The apparent shearviscosity of the dispersions was calculated at volume fractions ranging from0.31 to 0.56. Shear-thinning behavior was clearly observed at high volumefractions. The low- and high-limiting viscosities were then estimated from theapparent viscosity by fitting these data into a semi-empirical formula.Furthermore, the short-time motions were examined for Brownian particlesfluctuating in concentrated dispersions, for which the fluid inertia plays animportant role. The mean square displacement was monitored in the vorticitydirection at several different Peclet numbers and volume fractions so that theparticle diffusion coefficient is determined from the long-time behavior of themean square displacement. Finally, the relationship between the non-Newtonianviscosity of the dispersions and the structural relaxation of the dispersedBrownian particles is examined.
展开▼
