Journal ArticleDOI
Kinetic theories for granular flow: inelastic particles in Couette flow and slightly inelastic particles in a general flowfield
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In this paper, the authors studied the flow of an idealized granular material consisting of uniform smooth, but nelastic, spherical particles using statistical methods analogous to those used in the kinetic theory of gases.Abstract:
The flow of an idealized granular material consisting of uniform smooth, but nelastic, spherical particles is studied using statistical methods analogous to those used in the kinetic theory of gases. Two theories are developed: one for the Couette flow of particles having arbitrary coefficients of restitution (inelastic particles) and a second for the general flow of particles with coefficients of restitution near 1 (slightly inelastic particles). The study of inelastic particles in Couette flow follows the method of Savage & Jeffrey (1981) and uses an ad hoc distribution function to describe the collisions between particles. The results of this first analysis are compared with other theories of granular flow, with the Chapman-Enskog dense-gas theory, and with experiments. The theory agrees moderately well with experimental data and it is found that the asymptotic analysis of Jenkins & Savage (1983), which was developed for slightly inelastic particles, surprisingly gives results similar to the first theory even for highly inelastic particles. Therefore the ‘nearly elastic’ approximation is pursued as a second theory using an approach that is closer to the established methods of Chapman-Enskog gas theory. The new approach which determines the collisional distribution functions by a rational approximation scheme, is applicable to general flowfields, not just simple shear. It incorporates kinetic as well as collisional contributions to the constitutive equations for stress and energy flux and is thus appropriate for dilute as well as dense concentrations of solids. When the collisional contributions are dominant, it predicts stresses similar to the first analysis for the simple shear case.read more
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A turbulence model for rapid flows of granular materials part II. Simple shear flows
D. Ma,Goodarz Ahmadi +1 more
TL;DR: Using the one-equation turbulence model of Part I, rapid flows of granular materials are studied in this paper, where the equations governing the transport of mass, linear momentum and fluctuation energy are considered.
Journal ArticleDOI
Grid independence behaviour of fluidized bed reactor simulations using the Two Fluid Model: Detailed parametric study
TL;DR: In this paper, the grid independence behavior of the Two Fluid Model in reactive bubbling fluidized bed simulations has been investigated and the relationship between the particle relaxation time and the sufficiently grid independent cell size has been established.
Journal ArticleDOI
CFD simulations of a full-loop CFB reactor using coarse-grained Eulerian–Lagrangian dense discrete phase model: Effects of modeling parameters
TL;DR: In this article, the hydrodynamics of a 3D full-loop circulating fluidized bed (CFB) reactor were investigated using a coarse-grained dense discrete phase model (DDPM).
Journal ArticleDOI
Space-dependent kinetics simulation of a gas-cooled fluidized bed nuclear reactor
Christopher C. Pain,Jefferson L. M. A. Gomes,M. D. Eaton,C.R.E. de Oliveira,Adrian Umpleby,A.J.H. Goddard,H. van Dam,T.H.J.J. van der Hagen,Danny Lathouwers +8 more
TL;DR: In this paper, numerical simulations of a conceptual helium-cooled fluidized bed thermal nuclear reactor are performed using the coupled neutronics/multi-phase computational fluid dynamics code finite element transient criticality which is capable of modelling all the relevant nonlinear feedback mechanisms.
References
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Journal ArticleDOI
Equation of State for Nonattracting Rigid Spheres
TL;DR: In this paper, a new equation of state for rigid spheres has been developed from an analysis of the reduced virial series, which possesses superior ability to describe rigid-sphere behavior compared with existing equations.
Journal ArticleDOI
Experiments on a Gravity-Free Dispersion of Large Solid Spheres in a Newtonian Fluid under Shear
TL;DR: In this article, a large number of spherical grains of diameter D = 0.13 cm were sheared in Newtonian fluids of varying viscosity (water and a glycerine-water-alcohol mixture) in the annular space between two concentric drums.
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