Evaluation of lubrication force on colliding particles for DEM simulation of fluidized beds

Zhang, Wenbin; Noda, Reiji; Horio, Masayuki

doi:10.1016/j.powtec.2005.04.021

Cited by 43 publications

(22 citation statements)

References 17 publications

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“…Zhang et al 14 applied the lubrication analysis to gas-solid interactions and calculated the restitution coefficient after accounting for the surface roughness of the spheres, noncontinuum behavior of the fluid, and van der Waals attractive forces. Consistent with the theory of Davis et al, 1 Zhang et al 14 found that the lubrication forces in gas-solid flows could not be neglected at low Stokes numbers.…”

Section: Introductionsupporting

confidence: 56%

Initial rates of aggregation for dilute, granular flows of wet particles

2009

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Molecular dynamics (MD) simulations are used to determine the agglomeration rates of wet grains (particles coated with a viscous, liquid layer) engaged in simple shear flow under dilute conditions. In this work, a closed-form model derived from the elastohydrodynamic theory describes the normal restitution coefficient for binary collisions. Unlike previous MD studies, the particle deformation is not assumed to depend on a particle “overlap” (penetration), but instead depends on the formal coupling of Hertzian deformation theory with lubrication theory. The initial rate of doublet formation is studied as a function of system properties and the energy input to the system. In addition to the system properties, the distribution of relative velocities in the system is found to be a key factor influencing the initial rates of clustering. A theory based on estimating the collision frequency and the critical velocity below which no rebound is observed—due to viscous dissipation—is found to provide a good approximation of the initial aggregation rate. The rate of aggregation is found to increase with increasing number of particles in the system, increasing solid fraction, decreasing overall Stokes number, and decreasing compliance parameter.

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Section: Introductionsupporting

confidence: 56%

Initial rates of aggregation for dilute, granular flows of wet particles

2009

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“…Figure 6 shows a non-linear curve of coefficient of restitution versus Stokes number for a small sand particle and a range of fluid types considered in this study. Figure 6 also compares the results obtained in PFC 2D with semi-empirical model developed by Zhang et al (2005). The comparison shows that Davis's model has sufficient accuracy without implementing the surface roughness of a single sand particle and the types of fluid in this study.…”

Section: Model Verificationmentioning

confidence: 87%

“…6). A discrepancy related to the critical Stokes number value between theoretical and experimental values was found due to the elastic properties and asperity interactions of the spheres (Joseph and Hunt 2004;Joseph et al 2001;Zhang et al 2005). Motion of particles after collision is divided into normal and tangential components.…”

Section: Model Verificationmentioning

confidence: 96%

“…The applicability of this model to the real particle settling situation has several drawbacks. The lubrication theory was originally tested on steel and glass spheres, with several studies that take into account particle surface roughness (Zhang et al 2005). In terms of elastic response, it can be assumed that sand particles behave similar to steel and a significant plastic deformation is not likely to occur during proppant placement.…”

Section: Model Verificationmentioning

confidence: 99%

“…Table 1 shows the results of one-particle drop tests with the particle lubrication user-defined contact model with three different Fig. 6 PFC results using the user-defined immersed contact model of wall and sand particle (r = 0.3 mm) after theory developed by Davis (1986) and Zhang et al (2005) model a) h min /h 0 = 1/5, b h min /h 0 = 1/10 and c h min /h 0 = 1/20, where h min is the particle surface roughness and h 0 is the particle radius fluids. The numerical results are compared with theoretical predictions commonly used for proppant flow and transport (Novotny 1977).…”

Section: Model Verificationmentioning

confidence: 99%

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Micromechanics of proppant agglomeration during settling in hydraulic fractures

Tomac

Gutierrez

2015

J Petrol Explor Prod Technol

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The micromechanics of proppant settling in quiescent fluid in a rough and relatively narrow rock fracture is investigated. The study focuses on particleparticle and particle-wall interactions in a dense-phase particle settling. The study used a coupled discrete element method and computational fluid dynamics (DEM-CFD) code because DEM-CFD is the most suitable computational method for modeling the frequent interactions of dense assembly of rigid particles and enables modeling of two-way solid-fluid interactions. Due to frequent particleparticle interactions of grains submerged in fluids, the particle interaction model in DEM is improved by the incorporation of the effects of lubrication due to a layer of fluid surrounding particles. Results of the numerical study are compared to previous experimental and theoretical relationships. The findings of the study highlight conditions that lead to proppant aggregation due to the fluid viscosity and fracture width in relation to particle diameter ratio. In the light of the DEM-CFD results, it was found that published relationships are inadequate in describing the settling rates for proppant in a rough and narrow hydraulic fracture and high fluid viscosity. Micromechanical particle interactions during settling and erratic upward and fluid counter-flow may cause proppant trajectories that are not always in the direction of gravity in a rough fracture resulting in clogging of the fracture or forming faster settling particle agglomerates. The maximum packing density 0.3-0.4 (3.9-5.9 lbs/gal) of proppant in a narrow and rough hydraulic fracture was obtained in this study, which is lower than the usually assumed one of 0.5 (9.8 lbs/gal) for any given fracture roughness.Keywords DEM-CFD Á Lubrication Á Fluid-solid coupling Á Dense-phase flow Á Proppant settling Á Hydraulic fracture List of symbols

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Biotechnology for Sustainable Remediation of Contaminated Wastewater

Hajam

2023

Aquatic Contamination

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Evaluation of lubrication force on colliding particles for DEM simulation of fluidized beds

Cited by 43 publications

References 17 publications

Initial rates of aggregation for dilute, granular flows of wet particles

Initial rates of aggregation for dilute, granular flows of wet particles

Micromechanics of proppant agglomeration during settling in hydraulic fractures

Biotechnology for Sustainable Remediation of Contaminated Wastewater

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