Flow instabilities in shear-thickening suspensions Nesta apresentação, investigaremos o surgimento de instabilidades devido a esse comportamento de enfraquecimento da velocidade em duas configurações hidrodinâmicas clássicas.Francisco Rocha Aix-Marseille University, CNRS, Laboratoire IUSTI, Marseille 13453, France em 27/07/2022 Abstract Shear thickening fluids are granular suspensions whose viscosity drastically increase as they are subjected to higher shear stresses or shear rates. During the past decade, there has been an increasing consensus that this behaviour is a reflect of a transition from a frictionless to a frictional state, mediated by a short-range repulsive force between the constituent particles. One of the consequences of this frictional transition is that the flow rules can be S-shaped, with regions of velocity-weakening (negatively sloped) rheology. In this presentation we will investigate the emergence of instabilities due to this velocity-weakening behaviour in two classical hydrodynamic configurations. In the first part of the talk we will discuss experiments with a floating layer of shear-thickening fluid in a wide-gap cylindrical Couette cell. Our experiments show that below a critical stress the suspension behaves as a quasi-Newtonian fluid, and above this critical value the flow becomes unsteady and marked by periodic jamming fronts that propagate through the material. For the second part, we will concentrate on the gravity-driven flow of a shear thickening suspension down an inclined plane. For solids volume fraction whose flow rules display velocity- weakening behaviour, the flow becomes unstable, triggering surface waves at a critical Reynolds number, much smaller than the threshold for the emergence of Kapitza waves. By applying a depth-integrated model, we show that the instability arises not from inertia, but from the coupling between free-surface deformations and the velocity-weakening rheology. This mechanism, which gives rise to a new class of kinematic waves without inertia, is very generic and could also be extended to other complex fluids displaying a velocity-weakening rheology (e.g. granular materials, geomaterials, etc). Local e Data Tema: Flow instabilities in shear-thickening suspensionsPalestrante: Francisco Rocha Aix-Marseille University, CNRS, Laboratoire IUSTI, Marseille 13453, FranceData: 27/07/2022 Secretaria Fale ConoscoRoteiros e ProcedimentosSolicitaçõesTelefones e e-mail Seminários Álgebra Análise Geometria Mecânica Sistemas Dinâmicos Teoria da Computação Teoria da Probabilidade Teoria dos Números
