A Fundamental Study of Dispersed Multiphase Flows at Small Scales

Acrivos, Andreas ; Khusid, Boris ; Koplik, Joel

City College of CUNY, New York, NY

关键词: Multiphase Flow;    Nanochannel;    Free Energy;    36 Materials Science;    Velocity Particle Transport;   

DOI  :  10.2172/839346
RP-ID  :  DOE/ER/46068
RP-ID  :  FG02-03ER46068
RP-ID  :  839346

美国|英语

来源: UNT Digital Library

【 摘 要 】

The purpose of the research supported by this grant was two-fold: I, to continue our earlier studies on the rheology of suspensions of non-colloidal particles; and, II, to study the transport of a nano-sized particle through a fluid-filled nano-channel using molecular dynamics simulations. In I, we investigated, by means of Stokesian Dynamics simulations, the dynamics of concentrated suspensions and discovered that their statistical properties could be described, even for particle concentrations up to 20%, by means of an analytical theory of pair-particle interactions, provided that pair-doublets are assumed to be totally absent. We also provided a quantitative explanation of the fascinating banding phenomenon of particle axial segregation which was observed when a suspension of neutrally buoyant particles was sheared in a partially filled horizontal Couette device or in a rotating horizontal cylinder. In II, independently of the shape and the relative size of the particle, we find two distinct regimes as a function of the degree of wetting, with a sharp transition between them. Specifically, in a highly wetting suspending fluid, the particle moves through the cylinder with an average axial velocity in agreement with that obtained from the solution of the continuum Stokes equations. In contrast, in the case of less-wetting fluids, only the early time motion of the particle is consistent with continuum dynamics. At later times, the particle is eventually adsorbed onto the wall and subsequently executes an intermittent stick-slip motion. Also, the force on the particle and the system's Helmholtz free energy are found to depend on the particle's history as well as on its radial position and the wetting properties of the fluid.