Orateur : Bruno Chareyre
Laboratoire 3S-R, UMR 5521, Grenoble
Titre : "Micro-hydromechanical couplings in numerical models with applications to dense granular suspensions"
Date et lieu : le 7 Novembre à 11h, salle 250 IUSTI
Résumé : The interactions between fluids and particles at high solid fractions are discussed, and different ways to reflect them in numerical models are commented.
Adopting the point of view of continuum mechanics, the so-called poromechanical coupling is discussed first. This strong two-way coupling results from the mass balance equation (in fact volume balance for incompressible phases) and is well known in the theory of porous media. A particle-scale counterpart of the volume balance equation is introduced in a discrete element model (DEM) and classical poromechanical problems such as consolidation and liquefaction are revisited. Poromechanical effects are not sufficient to explain the bulk viscosity of grain-fluid mixtures, and we suggest that it corresponds to keeping only the long range terms that appear in the Stokesian Dynamics (SD) approach. We therefore retain the short range terms of SD and we introduce them as additional interactions in the the DEM model. This combination result in a very efficient numerical schemes compared to SD or typical CFD couplings. It is found that this model is able to match rheometer experiments at constant P (Boyer et al.). Through parametric studies, the behavior of sheared suspensions is investigated. The study includes the transient regime after a change of the shear rate and the steady state at constant shear rate. The contributions of solid contacts and hydrodynamic interactions to the bulk shear stress are analyzed, and the evolution of the microstructure is presented.