Rheology of Colloidal Particles in a Confined Channel under Shear Flow by Brownian Dynamic Simulations
✍ Scribed by Miguel Angel Valdez; Octavio Manero
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 260 KB
- Volume
- 190
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
liquids (2) and specifically by the Derjaguin-Landau-Ver-A colloidal system of strongly charged particles, confined bewey-Oberbeek (DLVO) model to account for the interactween two charged walls, is studied under static conditions and tions between colloidal particles in the bulk (3). However, in the presence of shear flows. Brownian Dynamics simulations the interaction forces between colloidal particles and charged (BD) are used to determine the concentration profiles for several walls have not been considered to the same extent. Experiseparations of charged walls. Results show good agreement with ments have shown several interesting features of the induced those obtained under static conditions using the Hypernetted structure near the charged walls due to these forces (4).
Chain Approximation (HNC) and Monte Carlo simulations. Re-
Dilute colloidal suspensions of strongly charged particles
sults obtained with BD and HNC for neutral walls show more in equilibrium, placed between charged walls, have been similarities than those between BD and Monte Carlo simulations depending on the initial state of the colloidal particles. The pres-recently studied (5), using models and theoretical approxience of a shear flow field perturbs the equilibrium concentration mations contained in the equilibrium theory of inhomogenprofiles and the distribution function in the flow direction, generateus fluids (e.g., hypernetted chain approximation (HNC), ing a structureless system, as confirmed by the absence of peaks Rogers-Young (RY)) and also using computational simulain the radial distribution function. The mobility of the particles in tions (e.g., Monte Carlo). Results show that highly repulsive the transversal direction decreases rapidly and becomes practically charged walls expel the particles from an adjacent layer of frozen. The flow exhibits a non-Newtonian behavior with shearthickness d, whose magnitude depends on the strength of thinning viscosity. Due to the interparticle interactions and partithe wall-particle repulsion, and moreover, the structure becle-wall interactions, the viscosity is lower as the wall separation yond this distance depends only on the bulk properties of decreases, giving rise to an apparent slip in the colloidal suspenthe suspension. In addition, the presence of monolayers of sion. The slip velocity for repulsive walls is higher than that obcolloidal particles adjacent to the walls was found to depend tained with neutral walls and increases with the shear stress according to a power law, as observed in polymer solutions. The on whether the strength of the wall-particles repulsion is shear viscosity and the normal stress differences depend strongly weak, neutral, or attractive (6).
on the combined effect of confinement, concentration of particles, In flowing colloidal suspensions, Brownian Dynamic magnitudes of inter-particle interactions and wall-particle repul-(BD) simulations have provided a very useful tool to undersion.