Lattice-Boltzmann simulation of the sedimentation of charged disks

Abstract

We report a series of lattice-Boltzmann simulations of the sedimentation velocity of charged disks. In these simulations, we explicitly account for the hydrodynamic and electrostatic forces on disks and on their electrical double layer. By comparing our results with those for spheres with equal surface and charge, we can clarify the effect of the particle shape on the sedimentation process. We find that disks and spheres exhibit a different dependence of the sedimentation velocity on the Debye screening length. An analysis of the behavior of highly charged disks ͑beyond the scope of the linearized Poisson-Boltzmann equation͒ shows that, in that regime, the charge dependence of the sedimentation velocity of disks and spheres is similar. This suggests that, at high charge, the effective hydrodynamic shape of the disks becomes more spherical.

Translational and rotational dynamics of colloidal rods by direct visualization with confocal microscopy

“…Deviations due to charge are difficult to quantitatively estimate for non-spherical particles. As a point of reference, a recent study for charged disks of aspect ratio 5-10 suggests no effect of charge for Debye layers that are asymptotically thick or thin relative to the largest dimension of the particle [32]. However, deviations in the dilute friction coefficient that depend on aspect ratio and degree of charge are found for Debye layers of intermediate thickness due to the interplay between hydrodynamic dissipation and electrolyte diffusion.…”

Simulating (electro)hydrodynamic effects in colloidal dispersions: Smoothed profile method

“…Further application of the SP method to electrophoresis of concentrated suspensions is reported elsewhere [36]. of macromolecules of other shapes, such as disks [19], rods, and others, and other constitutive models for solvents is straightforward.…”

“…Hydrodynamic simulations of ions and/or charged colloids have been proposed by making use of some of the above schemes [14,15,16,17,18,19]. Nonetheless, the tractability and/or physical validity of their modeling remain controversial.…”

“…In Refs. [16,17,18,19], they adopted the lattice Boltzmann (LB) method for explicitly solving the solvent hydrodynamics. Although the LB method has many advantages for solving large systems, compared to the standard discretization schemes, the applicability to various constitutive equations for the complex fluids other from the Newtonian fluids is unveiled.…”

Determination of the zeta potential for highly charged colloidal suspensions

“…The electrostatic potential is computed using a successive over-relaxation (SOR) scheme [16]. This method has been successfully applied to analyse different dynamical processes involving suspensions of charged objects [17][18][19][20].…”