Mesoscale hydrodynamic modeling of a colloid in shear-thinning viscoelastic fluids under shear flow

In order to study the dynamics of colloidal suspensions with viscoelastic solvents, a simple mesoscopic model of the solvent is required. We propose to extend the multiparticle collision dynamics (MPC) technique-a particle-based simulation method, which has been successfully applied to study the hydrodynamic behavior of many complex fluids with Newtonian solvent-to shear-thinning viscoelastic solvents. Here, the normal MPC particles are replaced by dumbbells with finite-extensible nonlinear elastic (FENE) springs. We have studied the properties of FENE-dumbbell fluids under simple shear flow with shear rate (gamma)over dot. The stress tensor is calculated, and the viscosity eta and the first normal-stress coefficient psi(1) are obtained. Shear-thinning behavior is found for reduced shear rates Gamma = (gamma)over dot tau > 1, where tau is a characteristic dumbbell relaxation time. Here, both eta and psi(1) display power-law behavior in the shear-thinning regime. Thus, the FENE-dumbbell fluid with MPC collisions provides a good description of viscoelastic fluids. As a first application, we study the flow behavior of a colloid in a shear-thinning viscoelastic fluid in two dimensions. A slowing down of the colloid rotation in a viscoelastic fluid compared to a Newtonian fluid is obtained, in agreement with recent numerical calculations and experimental results. (C) 2011 American Institute of Physics. [doi:10.1063/1.3646307]