Simulating the rheology of dense colloidal suspensions using dissipative particle dynamics

Abstract

The rheological properties of colloidal suspensions of spheres, rods, and disks have been studied using a mesoscopic simulation technique, known as dissipative particle dynamics ͑DPD͒. In DPD, a suspension is modeled as a system of large colloidal particles in a liquid of interacting point particles. For the calculation of hydrodynamic interactions, this method is computationally more efficient than conventional techniques using a continuum model for the solvent. Applying a steady-shear rate to the particulate suspensions, we have measured the viscosity as a function of shear rate and volume fraction of the suspended particles. The viscosity of a 30 vol % suspension of spheres displays characteristic shear-thinning behavior as a function of increasing shear rate. The values for the high-and low-shear viscosity are in good agreement with experimental data. For higher particulate densities good results are obtained for the high-shear viscosity, although the viscosity at low-shear rates shows a dependence on the size of the suspended spheres that we attribute to finite size effects. Dilute suspensions of rods and disks show intrinsic viscosities which are in excellent agreement with theoretical predictions. For concentrated suspensions of both rods and disks, the viscosity increases with the third power of the volume fraction. We find the same scaling behavior as predicted by Doi and Edwards ͓M. Doi and S. F. Edwards, The Theory of Polymer Dynamics ͑Oxford University Press, New York, 1986͔͒ for rod suspensions in the semidilute regime. The DPD simulation technique emerges as a useful tool for studying the rheology of particulate suspensions. ͓S1063-651X͑97͒08203-2͔

Modelling percolation in fibre and sphere mixtures: Routes to more efficient network formation

“…In this work, they showed that the temperature of the system was directly related to the amplitude of the noise by means of a fluctuation dissipation theorem. Since then, DPD has been used to model wide variety of problems including, for example, shear thinning behaviour of polymer solutions [37], prediction of phase separation [38], and the suspension phenomenology of particles with different shapes [39][40][41].…”

Strongly overdamped Dissipative Particle Dynamics for fluid-solid systems

“…A suspended particle of spherical/circular shape can be modelled using a single DPD particle [15][16][17][18][19]8] or a set of frozen DPD particles [20][21][22][23]. The single particle model involves three groups of DPD parameters: the first group associated with the interactions between solventsolvent particles, the second with solvent-colloidal particles and the third with colloidalcolloidal particles.…”

From Molecular Dynamics to Dissipative Particle Dynamics

“…Applications of the technique include colloidal suspensions [4], polymer solutions [5] and binary immiscible fluids [6]. For specific applications where comparison is possible, this model is orders of magnitude faster than MD [7].…”

“…Here the computational effort is adapted to meet the local need for detail of description: it is larger in narrow regions between the particles than in the bulk. Previous DPD simulations have had difficulty with dense colloidal suspensions precisely because the technique is unable to handle multiple lengthscale phenomena [4]. Other complex systems where modeling and simulation frequently involve several simultaneous length scales include polymeric and amphiphilic fluids, particularly in porous media and restricted geometries [11].…”

“…[8,12,16] the magnitudes ofF kl andq kl are obtained on the basis of the Fokker-Planck equation which derives from equations like Eqs. (4). The isothermal results, adapted to the present case, are the fluctuation dissipation relations ω 2 kl = 2ω 2 kl⊥ = 4ηk B T (l kl /r kl ) for the forceF kl and for the heat fluctuations Λ 2 kl = 2k B T λ(l kl /r kl ) [16].…”