The role of particle collisions in pneumatic transport

Louge, Michel Y.; Mastorakos, Epaminondas; Jenkins, James T.

doi:10.1017/s0022112091003427

Cited by 222 publications

(139 citation statements)

References 20 publications

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“…Nevertheless, in the dilute suspension limit, these hydrodynamic interactions become less relevant [19,20] and only the isolate body resistance is retained, usually in the form of a simple drag force. On the other hand, due to the inherent complexity of the interaction between the interstitial fluid and the granular particles, early kinetic theory studies have neglected in most cases the effect of inelasticity in suspended particle collisions [23][24][25][26][27]. This kind of approach is not entirely accurate since of course in most real cases the sizes of suspended particles are big enough to render particle collisions inelastic (bigger than 1 µm, otherwise particles may be considered as colloids, for which collisions are elastic [22,28]).…”

Section: Introductionmentioning

confidence: 99%

Non-Newtonian hydrodynamics for a dilute granular suspension under uniform shear flow

2015

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We study in this work a steady shearing laminar flow with null heat flux (usually called "uniform shear flow") in a gas-solid suspension at low density. The solid particles are modeled as a gas of smooth hard spheres with inelastic collisions while the influence of the surrounding interstitial fluid on the dynamics of grains is modeled by means of a volume drag force, in the context of a rheological model for suspensions. The model is solved by means of three different but complementary routes, two of them being theoretical (Grad's moment method applied to the corresponding Boltzmann equation and an exact solution of a kinetic model adapted to granular suspensions) and the other being computational (Monte Carlo simulations of the Boltzmann equation). Unlike in previous studies on granular sheared suspensions, the collisional moment associated with the momentum transfer is determined in Grad's solution by including all the quadratic terms in the stress tensor. This theoretical enhancement allows us for the detection and evaluation of the normal stress differences in the plane normal to the laminar flow. In addition, the exact solution of the kinetic model gives the explicit form of the velocity moments of the velocity distribution function. Comparison between our theoretical and numerical results shows in general a good agreement for the non-Newtonian rheological properties, the kurtosis (fourth velocity moment of the distribution function) and the velocity distribution of the kinetic model for quite strong inelasticity and not too large values of the (scaled) friction coefficient characterizing the viscous drag force. This shows the accuracy of our analytical results that allows us to describe in detail the flow dynamics of the granular sheared suspension.

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Section: Introductionmentioning

confidence: 99%

Non-Newtonian hydrodynamics for a dilute granular suspension under uniform shear flow

2015

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“…The turbulent multiphase flows, complicated by the presence of hard-to-quantify interactions between phases, are also a widely pursued research subject [29][30][31]. Due to the stochastic nature of turbulence in multiphase flows emanating from both the carrier-phase turbulence and from the interaction of dispersed phase particles with the carrier phase (also sometimes referred to as pseudo-turbulence) [32][33][34][35], the problem of turbulent multiphase flow is far more complex than its single-phase counterpart. Quantification of pseudoturbulence (carrier phase velocity fluctuations due to dispersed phase) has been mostly limited to sub-Kolmogorov [31,[36][37][38] scales and only recent studies have extended such analysis to large particles [32,35] using Particle-Resolved Direct Numerical Simulations (PR-DNS)…”

Section: Challenges and Technical Gapsmentioning

confidence: 99%

“…This led to the development of one-equation model [34], followed by two-equation model [33], and then followed by more sophisticated k-ε model [39,40]. It should be noted that these models are basically extended versions of single-phase k-ε models modified to be used in gas-solids flows, and by design, are limited to very dilute regimes only.…”

Section: Challenges and Technical Gapsmentioning

confidence: 99%

Technical Report on NETL's Non Newtonian Multiphase Slurry Workshop: A path forward to understanding non-Newtonian multiphase slurry flows

Guenther¹,

Garg²

2013

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“…In general, such sensitivity to model parameters points to a breakdown of the hydrodynamic description for relatively dilute flows. 1 For turbulent flow, a one-equation turbulence model 11 has been used to describe the gas-phase turbulence by adopting standard wall-functions for the zone near the wall. A zeroequation closure 12 for the gas-phase turbulence has also been proposed.…”

Section: ■ Introductionmentioning

confidence: 99%

Simulation of Mono- and Bidisperse Gas-Particle Flow in a Riser with a Third-Order Quadrature-Based Moment Method

Passalacqua¹,

Fox²

2012

Ind. Eng. Chem. Res.

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Gas-particle flows can be described by a kinetic equation for the particle phase coupled with the Navier−Stokes equations for the fluid phase through a momentum exchange term. The direct solution of the kinetic equation is prohibitive for most applications due to the high dimensionality of the space of independent variables. A viable alternative is represented by moment methods, where moments of the velocity distribution function are transported in space and time. In this work, a fully coupled third-order, quadrature-based moment method is applied to the simulation of mono-and bidisperse gas-particle flows in the riser of a circulating fluidized bed. Gaussian quadrature formulas are used to model the unclosed terms in the moment transport equations. A Bhatnagar−Gross−Krook (BGK) collision model is used in the monodisperse case, while the full Boltzmann integral is adopted in the bidisperse case. The predicted values of mean local phase velocities, rms velocities, and particle volume fractions are compared with the Euler−Lagrange simulations and experimental data from the literature. The local values of the time-average Stokes, Mach, and Knudsen numbers predicted by the simulation are reported and analyzed to justify the adoption of high-order moment methods as opposed to models based on hydrodynamic closures. ABSTRACT: Gas-particle flows can be described by a kinetic equation for the particle phase coupled with the Navier−Stokes equations for the fluid phase through a momentum exchange term. The direct solution of the kinetic equation is prohibitive for most applications due to the high dimensionality of the space of independent variables. A viable alternative is represented by moment methods, where moments of the velocity distribution function are transported in space and time. In this work, a fully coupled third-order, quadrature-based moment method is applied to the simulation of mono-and bidisperse gas-particle flows in the riser of a circulating fluidized bed. Gaussian quadrature formulas are used to model the unclosed terms in the moment transport equations. A Bhatnagar−Gross−Krook (BGK) collision model is used in the monodisperse case, while the full Boltzmann integral is adopted in the bidisperse case. The predicted values of mean local phase velocities, rms velocities, and particle volume fractions are compared with the Euler−Lagrange simulations and experimental data from the literature. The local values of the time-average Stokes, Mach, and Knudsen numbers predicted by the simulation are reported and analyzed to justify the adoption of high-order moment methods as opposed to models based on hydrodynamic closures. Disciplines Biological Engineering | Chemical Engineering Comments

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The role of particle collisions in pneumatic transport

Cited by 222 publications

References 20 publications

Non-Newtonian hydrodynamics for a dilute granular suspension under uniform shear flow

Non-Newtonian hydrodynamics for a dilute granular suspension under uniform shear flow

Technical Report on NETL's Non Newtonian Multiphase Slurry Workshop: A path forward to understanding non-Newtonian multiphase slurry flows

Simulation of Mono- and Bidisperse Gas-Particle Flow in a Riser with a Third-Order Quadrature-Based Moment Method

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