Séminaire de Mécanique d'Orsay

Le 20 juin 2024 à 14h00 - Salle des séminaires FAST-LPTMS (Bât. 530, salle C.120, 1er)

Flowing dense suspensions

Philippe Bourrianne

Colloidal suspensions, present in a multitude of common liquids such as paints, inks or even food products, are known to exhibit a wide range of rheological behaviors from shear-thinning to yield stress fluids. At large concentrations, dense suspensions are known for their ability to block and resist flows. In particular, discontinuous shearthickening denotes a reversible and brutal increase in viscosity under external shear. By dispersing fumed silica particles into polypropylene glycol, we will first describe a model suspension exhibiting a variety of controllable rheological regimes including shearthinning, yield stress to shear-thickening at low volume fraction due to the particle geometry. We will specifically show how we can tune the shear-thickening transition by playing on the frictional interactions between particles. While the steady-state rheology of dense suspensions has been extensively studied, the dynamics of the shear-thickening transition remain to be described. By filling thin elastic shells with shear-thickening suspensions, we will study the rapid deformation of capsules during their impact on a solid substrate. Liquid-filled elastic capsules are known as an analogue of liquid drops during impact. We will first describe the influence of the liquid viscosity on the spreading of capsules filled with Newtonian liquids. We will then show how the dynamics of the deformation of a capsule is dramatically altered in the case of a shear-thickening content. We will thus demonstrate how those observations provide access to rheological measurements and rare insights into the dynamics of solidification during the shear-thickening transition. Finally, we will discuss further the influence of particles geometry in blocking events in a fluid by investigating the clogging of a dense suspension of non-convex particles in a 2D microfluidic Hopper. We will show how the interlocking between particles enhances dramatically the formation of solid-like structures close to a constriction.

Accès Salle des séminaires FAST-LPTMS (Bât. 530, salle C.120, 1er)