Modeling of dense granular flows: experiments, numerical simulations and stability analyses

Abstract

The flow of granular matter in dense regime is frequently found in both nature and industry. In nature, some examples are the erosion of river banks, the formation and migration of dunes in deserts, and landslides, for example. In industry, it occurs in pharmaceutical, agro-food, and pollution dispersion processes. Although of practical importance, dense granular flows are not well understood. This project proposes an experimental, numerical and theoretical study concerning the physics of granular flows in dense regime, and their interaction with fluids. The experiments will be performed in different configurations (granular beds sheared by a fluid, fluidized beds, and gravitational flows). For the experiments, we will film the different granular flows with a high-speed camera, and automatically identify and track the grains and clusters along images by using numerical scripts. In addition, when in the presence of liquids, the fluid instantaneous velocities will be measured with PIV (Particle Image Velocimetry), and flow visualization. For the numerical part, we will perform simulations using a coupled CFD-DEM (computational fluid dynamics - discrete element method) code. For the analytical part, stability analysis and perturbation methods will be employed. The objective is to identify and measure the mechanisms involved in each flow configuration, such as particle-particle shocks and friction, pressure and viscous drags, virtual mass force, and particle-wall shocks and friction, and then search for new physical models applied to an ensemble of grains for different dense granular flows. This project is an extension a FAPESP grant coordinated by the proponent (FAPESP Proccess n. 2016/13474-9); therefore, some of the information herein is found in the referred process. (AU)