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Polish Academy of Sciences

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G. Naegele



Recent publications
1.  Abade G.C., Cichocki B., Ekiel-Jeżewska M.L., Naegele G., Wajnryb E., Diffusion, sedimentation, and rheology of concentrated suspensions of core-shell particles, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3689322, Vol.136, pp.104902-1-16, 2012

Abstract:
Short-time dynamic properties of concentrated suspensions of colloidal core-shell particles are studied using a precise force multipole method which accounts for many-particle hydrodynamic interactions. A core-shell particle is composed of a rigid, spherical dry core of radius a surrounded by a uniformly permeable shell of outer radius b and hydrodynamic penetration depth κ−1. The solvent flow inside the permeable shell is described by the Brinkman-Debye-Bueche equation, and outside the particles by the Stokes equation. The particles are assumed to interact non-hydrodynamically by a hard-sphere no-overlap potential of radius b. Numerical results are presented for the high-frequency shear viscosity, η∞, sedimentation coefficient, K, and the short-time translational and rotational self-diffusion coefficients, D t and D r. The simulation results cover the full three-parametric fluid-phase space of the composite particle model, with the volume fraction extending up to 0.45, and the whole range of values for κb, and a/b. Many-particle hydrodynamic interaction effects on the transport properties are explored, and the hydrodynamic influence of the core in concentrated systems is discussed. Our simulation results show that for thin or hardly permeable shells, the core-shell systems can be approximated neither by no-shell nor by no-core models. However, one of our findings is that for κ(b − a) ≳ 5, the core is practically not sensed any more by the weakly penetrating fluid. This result is explained using an asymptotic analysis of the scattering coefficients entering into the multipole method of solving the Stokes equations. We show that in most cases, the influence of the core grows only weakly with increasing concentration.

Keywords:
core-shell particles, suspension, diffusion, sedimentation, effective viscosity

Affiliations:
Abade G.C. - Universidade de Brasilia (BR)
Cichocki B. - University of Warsaw (PL)
Ekiel-Jeżewska M.L. - IPPT PAN
Naegele G. - other affiliation
Wajnryb E. - IPPT PAN

List of chapters in recent monographs
1. 
Cichocki B., Ekiel-Jeżewska M.L., Naegele G., Wajnryb E., Drops and Bubbles in Contact with Solid Surface, rozdział: Hydrodynamic Interactions Between Solid Particles at a Fluid-Gas Interface, Ferrari M., Liggieri L., Miller R., CRC Press, Leiden, pp.93-104, 2012

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