283059 Pair-Particle Dynamics in Sheared Colloidal Suspensions: Simulation and Theory

Monday, October 29, 2012
Hall B (Convention Center )
Ehssan Nazockdast, Chemical Engineering, Levich Institute, CCNY, New York, NY and Jeffrey F Morris, Levich Institute and Chemical Engineering, Levich Institute, City College of New York, New York, NY

We study the dynamics and microstructure of Brownian suspensions averaged to pair-particle level as a function of pair separation vector r.  This is carried out by sampling of configurations obtained from Accelerate Stokesian Dynamics simulation. The particles interact only through Brownian forces and hydrodynamic interactions with the Newtonian fluid. The dimensionless parameters defining the structure are the volume fraction, Φ, and Pectlet number, Pe, which is the ratio of hydrodynamic to Brownian forces. We report the average pair velocity and pair trajectory as well as fluctuating velocity field and dispersions around the average pair trajectory for a range of Pe and Φ. This work is motivated by the theory we have developed for prediction of microstructure of colloidal suspensions in simple-shear flow. The method determines the steady pair distribution function g(r) from a solution of the Smoluchowski equation reduced to pair level. The theory is based on number of assumption allowing for formulation of the pair relative convective and diffusive flux associated with hydrodynamic interactions of “bath” particles with the pair. The sampling results are compared against the predicted values for further insight and examination of the validity of the involved approximations. Finally the time-dependent microstructure and  rheology of colloidal suspensions is studied using the developed theory in flow conditions such as startup and oscillatory shear flows. 

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