1,721,025 research outputs found
Extended kinetic theory applied to dense, granular, simple shear flows.
Full text linkWe apply the extended kinetic theory (EKT) to the dense, simple shear flow of inelastic hard spheres. EKT is a phenomenological extension of kinetic theory which aims at incorporating in the simplest possible way the role of pre-collisional velocity correlations which are likely to occur at a concentration larger than the freezing point. The main effect of that correlation is the decrease in the rate at which fluctuating energy is dissipated in inelastic collisions. We use previously published results of numerical simulations performed using an event-driven algorithm to obtain analytical expressions for the radial distribution function at contact (which diverges at a concentration lower than the value at random close packing for sheared inelastic spheres) and the correlation length (i.e., the decreasing factor of the dissipation rate) at different values of the coefficient of restitution. With those, we show that when the diffusion of fluctuating energy of the particles is negligible, EKT implies that three branches of the analytical relation between the ratio of the shear stress to the pressure and the concentration (granular rheology) exist. Hence, for a certain value of the stress ratio, up to three corresponding values of the concentration are possible, with direct implications on the existence of multiple solutions to steady granular flows
Stilling Basins: Role of non-dimensional parameters in the spectral analysis of pressures over sills
No full textLaboratory investigation of dam-break flow of a mixture of water and granular matter
No full textSome preliminary experimental results concerning the velocity of the snout of a debris flow originating from the instantaneous opening of a sluice-gate (dam-break) in a rectangular flume are presented. The measurements have been performed by varying the slope and roughness of the channel bed and the amount of cohesionless solid material (gravel) mixed with water stored in a tank above the sluice-gate at the beginning of the test. It has been observed that the bed roughness does not immediately affect the evolution of the debris flow and its effects are seen only after a certain time from the opening of the sluice-gate. This observation provides a way to evaluate the time scale of the resistance force in the debris flow. Moreover, sometimes the dam-break wave evolves into a fully developed flow, allowing a quantitative description of the steady motion of a debris flow
Reologia lineare per il moto stazionario di un materiale granulare secco ad alta concentrazione
No full text- …
