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Fluid Dynamics
Colloquium
Monday, Oct 10th, 2005,
4:00 pm
Cullimore Lecture Hall, Room 611
New Jersey Institute of
Technology
Many-particle hydrodynamic interactions in
slit pores and thin liquid films
Jerzy Blawzdziewicz
Assistant Professor
Department of Mechanical Engineering, Yale University
Abstract
We will discuss the effects of confinement on equilibrium and non-equilibrium behavior of colloidal suspensions bounded by two planar walls or fluid interfaces. The first part of the presentation we will be focused on particle-stabilized thin liquid films. Owing to the presence of oscillatory structural forces produced by the particles, properties of such films are quite different than the properties of particle-free films. For example, particle stabilized films often form a stepwise structure with coexisting regions (phases) of uniform but different thickness. We describe equilibria between film phases using a quasi-two dimensional thermodynamic formalism in which the key quantity is the film tension. We show that the particle contribution to film tension results from the non-isotropy of the osmotic-pressure tensor in the film. The quasi 2d description is also generalized to non-equilibrium situations. We show that the motion of particle-stabilized films is analogous to the dynamics of a two-dimensional compressible fluid - the film thickness plays the role of mass density per unit area and film tension the role of pressure. In the linear-response regime, the film dynamics is characterized by the shear and extension viscosity coefficients as well as the lateral particle mobility coefficient. For a film stabilized by a suspension of hard spheres we have calculated these coefficients using a multipolar-expansion methods combined with a flow reflection technique. In the second part of the talk we will review our novel Cartesian-representation algorithm for evaluating hydrodynamic interactions in suspensions confined between two solid walls. Phenomena such as a large transverse friction coefficient of long chains of spheres and enhanced relative particle diffusion will be discussed.