Transport properties of monodisperse and bidisperse hard-sphere colloidal suspensions from multiparticle collision dynamics simulations

Abstract

The shear viscosities, long-time self-diffusion coefficients, and sedimentation velocities in monodisperse and bidisperse hard-sphere colloidal suspensions are simulated for volume fractions up to 0.40 using multiparticle collision dynamics with a discrete particle model. The bidisperse suspensions have diameter ratios of 2 and 4 and equal amounts of each particle by volume. All measured properties for monodisperse suspensions are found to be in good agreement with prior literature; however, they highlight the sensitivity of the simulation method to discretization effects. The sedimentation velocities for the bidisperse suspensions are also in reasonable agreement with prior literature, including direction reversal for the smaller particles when the diameter ratio is 4. This work provides reference data for transport properties of colloidal suspensions and establishes the suitability of multiparticle collision dynamics for modeling suspensions of particles with different sizes.

Figures (8)

• Figure 1: Particles with diameter $3\,\ell$, $6\,\ell$, and $12\,\ell$ along with their discretized surfaces. The number of surface particles for each was 42, 162, and 642, corresponding to surface densities of $1.49\,\ell^{-2}$, $1.43\,\ell^{-2}$, and $1.42\,\ell^{-2}$, respectively. The images were rendered using VMD 1.9.3 humphrey:jmg:1996.
• Figure 2: Simulated shear viscosity $\eta$ as a function of volume fraction $\phi$ for monodisperse suspensions of particles with diameter $d_1$. The dashed line is Eq. \ref{['eq:viscosity-mono']}.
• Figure 3: (a) Simulated long-time self-diffusion coefficient $D_1$ as a function of volume fraction $\phi$ for monodisperse suspensions of particles with diameter $d_1$. The dashed line is Eq. \ref{['eq:diffusion-mono']} with $D_{0,1}$ set to its theoretically expected value. (b) The same as (a) but the simulated $D_1$ is normalized by the simulated single-particle self-diffusion coefficient $D_{0,1}$. The open symbols are the Stokesian dynamics results of Ref. foss:jfm:1999.
• Figure 4: Test of the generalized Stokes--Einstein relationship between the simulated shear viscosity $\eta$ and long-time self-diffusion coefficient $D_1$ for monodisperse suspensions of particles with diameter $d_1$ using the data from Figs. \ref{['fig:viscosity-mono']} and \ref{['fig:diffusion-mono']}. The dashed line, $D_{0,1}/D_1 = \eta/\eta_0$, is the theoretical expectation.
• Figure 5: (a) Simulated sedimentation velocity $U_1$ as a function of volume fraction $\phi$ for monodisperse suspensions of particles with diameter $d_1$. The dashed line is Eq. \ref{['eq:sediment-mono']} with $U_{0,1}$ set to its theoretically expected value. The applied force $f_1$ was proportional to the particle volume with $f_1 = 0.5\,\varepsilon/\ell$ for $d_1 = 6\,\ell$. (b) The same as (a) but the simulated $U_1$ is normalized by the simulated single-particle sedimentation velocity $U_{0,1}$. The open symbols are the Stokesian dynamics results of Ref. wang:jcp:2015.