Abbas, Micheline and Climent, Eric and Simonin, Olivier Fully coupled simulations of noncolloidal monodisperse sheared suspensions. (2007) Chemical Engineering Research and Design, vol. 8 (n° 6). pp. 778791. ISSN 02638762

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Official URL: http://dx.doi.org/10.1205/cherd06114
Abstract
In this work we investigate numerically the dynamics of sheared suspensions in the limit of vanishingly small fluid and particle inertia. The numerical model we used is able to handle the multibody hydrodynamic interactions between thousands of particles embedded in a linear shear flow. The presence of the particles is modeled by momentum source terms spread out on a spherical envelop forcing the Stokes equations of the creeping flow. Therefore all the velocity perturbations induced by the moving particles are simultaneously accounted for. The statistical properties of the sheared suspensions are related to the velocity fluctuation of the particles. We formed averages for the resulting velocity fluctuation and rotation rate tensors. We found that the latter are highly anisotropic and that all the velocity fluctuation terms grow linearly with particle volume fraction. Only one offdiagonal term is found to be non zero (clearly related to trajectory symmetry breaking induced by the nonhydrodynamic repulsion force). We also found a strong correlation of positive/negative velocities in the shear plane, on a time scale controlled by the shear rate (direct interaction of two particles). The time scale required to restore uncorrelated velocity fluctuations decreases continuously as the concentration increases. We calculated the shear induced selfdiffusion coefficients using two different methods and the resulting diffusion tensor appears to be anisotropic too. The microstructure of the suspension is found to be drastically modified by particle interactions. First the probability density function of velocity fluctuations showed a transition from exponential to Gaussian behavior as particle concentration varies. Second the probability of finding close pairs while the particles move under shear flow is strongly enhanced by hydrodynamic interactions when the concentration increases.
Item Type:  Article 

Additional Information:  This publication is available on http://www.sciencedirect.com/science/journal/02638762 
Audience (journal):  International peerreviewed journal 
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Institution:  Université de Toulouse > Institut National Polytechnique de Toulouse  INPT Université de Toulouse > Université Paul SabatierToulouse III  UPS French research institutions > Centre National de la Recherche Scientifique  CNRS 
Laboratory name:  Institut de Mécanique des Fluides de Toulouse  IMFT (Toulouse, France)  EEC Laboratoire de Génie Chimique  LGC (Toulouse, France)  Génie des Interfaces & Milieux Divisés (GIMD) 
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Deposited By:  Eric Climent 
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