11:30 AM - 11:45 AM
[SCG46-10] Transition from viscous to inertial regime in dense frictional suspensions
Keywords:Granular, Rheology, Suspensions, Jamming, Friction
Failure and flow of granular materials are involved in many natural disasters and industrial processes. Several peculiar phenomena such as shear rate dependence behaviour, yield stress onset, normal stress difference, etc., distinguish them dramatically from classical newtonian flows. One of the most intriguing questions, which still remain a big challenge, are jamming-unjamming process and dissipation energy rate in a dense regime. Both of them seems to be strongly ruled by microscopic nature of inter-particle interaction forces and particle coupling with interstitial fluid. While hydrodynamic interactions or lubrication forces between the particles are important in the dilute regime, they become of lesser significance when the concentration is increased, and direct particle contacts become dominant in the rheological response. Despite its have been studied extensively, none of which is clearly understood so far.
Depending on boundary condition and stress distribution, dense granular flows can shows two different regimes : (i) rate-independent quasi-static flow, for moderate shear rate deformation, partially well described by continuous viscous-plastic models, inspired by soils mechanics, and (ii) rate-dependent behaviour, in which shear a normal stresses shows a power law function of the shear rate deformation in volume imposed rheology. In this frame of work, jamming transition is presented in a classical viscous approach as a shear viscosity divergence. In order to unifies theses two regimes, a non-classical rheology is suggested, wherein normal pressure, P, is imposed on the sample instead of the volume. Thus, a non-classical-frictional approach is suggested, in which the effective friction coefficient, defined by the ratio of macroscopic shear and normal stresses, and the flowable global solid-volume fraction are meanly controlled by an empirical power-law function of the ratio of macroscopic shear rate deformation and the normal pressure (perpendicular to the gradient direction). Moreover, particle-fluid coupling rules on the algebraical effective rheological properties of granular suspension; while for low viscosity interstitial fluid, the rheology has a high influence of inertial effect, newtonian rheology become important for high viscosity regime.
We present here an experimental study of viscous-inertial transition for a dense suspension of non-colloidal rigid PMMA particles by varying systematically the interstitial fluid viscosity for a both : Pressure and Volume-imposed rheology. The effect of inter-particle interaction is also explored by changing the elastic properties of solid particles by manufacturing soft hydrogel particles suspended in a water solution of UCON oil.
Depending on boundary condition and stress distribution, dense granular flows can shows two different regimes : (i) rate-independent quasi-static flow, for moderate shear rate deformation, partially well described by continuous viscous-plastic models, inspired by soils mechanics, and (ii) rate-dependent behaviour, in which shear a normal stresses shows a power law function of the shear rate deformation in volume imposed rheology. In this frame of work, jamming transition is presented in a classical viscous approach as a shear viscosity divergence. In order to unifies theses two regimes, a non-classical rheology is suggested, wherein normal pressure, P, is imposed on the sample instead of the volume. Thus, a non-classical-frictional approach is suggested, in which the effective friction coefficient, defined by the ratio of macroscopic shear and normal stresses, and the flowable global solid-volume fraction are meanly controlled by an empirical power-law function of the ratio of macroscopic shear rate deformation and the normal pressure (perpendicular to the gradient direction). Moreover, particle-fluid coupling rules on the algebraical effective rheological properties of granular suspension; while for low viscosity interstitial fluid, the rheology has a high influence of inertial effect, newtonian rheology become important for high viscosity regime.
We present here an experimental study of viscous-inertial transition for a dense suspension of non-colloidal rigid PMMA particles by varying systematically the interstitial fluid viscosity for a both : Pressure and Volume-imposed rheology. The effect of inter-particle interaction is also explored by changing the elastic properties of solid particles by manufacturing soft hydrogel particles suspended in a water solution of UCON oil.