Freely cooling granular gases with short-ranged attractive potentials

Murphy, Eric; Subramaniam, Shankar

doi:10.1063/1.4916674

Cited by 24 publications

(21 citation statements)

References 36 publications

(44 reference statements)

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“…For granular systems (no fluid) without gravity, the formation of clusters enhances agglomeration. Namely, in both free-evolving [20][21][22] and driven [23][24][25] systems, particles in clusters have higher collision frequency due to the increased local number density. Therefore, the collisional impact velocities (relative particle velocities prior to collisions) of particles in clusters decay faster than particles in the surrounding, lessdense regions [26,27].…”

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confidence: 99%

Cluster-Induced Deagglomeration in Dilute Gravity-Driven Gas-Solid Flows of Cohesive Grains

Liu

Hrenya

2018

Phys. Rev. Lett.

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Clustering is often presumed to lead to enhanced agglomeration between cohesive grains due to the reduced relative velocities of particles within a cluster. Our discrete-particle simulations on gravity-driven, gas-solid flows of cohesive grains exhibit the opposite trend, revealing a new mechanism we coin "cluster-induced deagglomeration." Specifically, we examine relatively dilute gas-solid flows, and isolate agglomerates of cohesive origin from overall heterogeneities in the system i.e., agglomerates of cohesive origin and clusters of hydrodynamic origin. We observe enhanced clustering with an increasing system size (as is the norm for noncohesive systems) as well as reduced agglomeration. The reduced agglomeration is traced to the increased collisional impact velocities of particles at the surface of a cluster i.e., higher levels of clustering lead to larger relative velocities between the clustered and nonclustered regions, thereby serving as an additional source of granular temperature. This physical picture is further evidenced by a theoretical model based on a balance between the generation and breakage rates of agglomerates. Finally, cluster-induced deagglomeration also provides an explanation for a surprising saturation of agglomeration levels in gravity-driven, gas-solid systems with increasing levels of cohesion, as opposed to the monotonically increasing behavior seen in free-evolving or driven granular systems in the absence of gravity. Namely, higher cohesion leads to more energy dissipation, which is associated with competing effects: enhanced agglomeration and enhanced clustering, the latter of which results in more cluster-induced deagglomeration.arXiv:1804.08074v2 [cond-mat.soft]

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confidence: 99%

Cluster-Induced Deagglomeration in Dilute Gravity-Driven Gas-Solid Flows of Cohesive Grains

Liu

Hrenya

2018

Phys. Rev. Lett.

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“…Murphy and Subramaniam [51] studied the homogeneous cooling state for a system of particles having an inelastic hard core associated with van der Waals potential. They obtained that the time evolution of the granular temperature obeys Haff's law in the initial stage and decreases faster as time goes on, then approaches to Haff's law for e = 0.…”

Section: Discussionmentioning

confidence: 99%

“…There exist some studies on the kinetic theory of gas molecules having the square well potential [43][44][45][46][47][48] in which, the collision processes are categorized into four processes: (i) hard core collisions, (ii) entering processes, (iii) leaving processes from the well, and (iv) trapping processes by the well [45,46,49]. Note that most of previous works study gases without dissipations in collisions except for some recent papers [50,51], which do not discuss the transport coefficients. It should also be noted that some papers developed the kinetic theory based on different models for cohesion [52,53].…”

Section: Introductionmentioning

confidence: 99%

Kinetic theory for dilute cohesive granular gases with a square well potential

2016

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“…Approximately 75% of particles in the sub-ensemble are in clusters HCG simulations are performed using the LAMMPS code (Plimpton, 1995) developed in Sandia National Lab. These simulations are performed in a periodic computational box in the same way as documented in (Murphy and Subramaniam, 2015). The simulations are performed in a domain size with L/d p = 50 for solid-phase volume fractions in the range 0.1 ≤ φ ≤ 0.4.…”

Section: Initialization Of Clustered Particle Configurationmentioning

confidence: 99%

Development of a gas–solid drag law for clustered particles using particle-resolved direct numerical simulation

Mehrabadi

Murphy

Subramaniam

2016

Chemical Engineering Science

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Particle-resolved direct numerical simulation (PR-DNS) is used to quantify the drag force on clustered particle configurations over the solid phase volume fraction range of 0.1 ≤ φ ≤ 0.35 and the mean slip Reynolds number range of 0.01 ≤ Re m ≤ 50. The particle configurations and flow parameters correspond to gas-solid suspensions of Geldart A particles in which formation of clusters have been reported. In our PR-DNS, we use clustered particle configurations that match cluster statistics observed in experimental studies.To generate the particle configurations, we perform discrete element method (DEM) simulations of homogeneous cooling gas (HCG) systems with cohesive and inelastic particles in the absence interstitial fluid. Clustered particle subensembles are then extracted from HCG simulations to match the statistics of cluster size distributions observed in experiments. These sub-ensembles are used for PR-DNS. It is found that the mean drag on clustered configurations decreases when compared to the drag laws for uniform particle configura- * tions. The maximum drag reduction belongs to the configuration with low solid-phase volume fraction φ = 0.1 in Stokes flow, and is about 35%. The drag reduction reduces with increase in both φ and Re m . A clustering metric is introduced to explain the behavior of the drag reduction with respect to solid-phase volume fraction. Also the behavior of the drag reduction with mean slip Reynolds number is related to the Brinkman screening length. PR-DNS results are then used to propose a clustered drag model for the range of flow parameters considered in this study. This clustered drag model provides a smooth transition between the uniform and clustered states by means of a weighting function with two model parameters.

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Freely cooling granular gases with short-ranged attractive potentials

Cited by 24 publications

References 36 publications

Cluster-Induced Deagglomeration in Dilute Gravity-Driven Gas-Solid Flows of Cohesive Grains

Cluster-Induced Deagglomeration in Dilute Gravity-Driven Gas-Solid Flows of Cohesive Grains

Kinetic theory for dilute cohesive granular gases with a square well potential

Development of a gas–solid drag law for clustered particles using particle-resolved direct numerical simulation

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