Computationally generated constitutive models for particle phase rheology in gas-fluidized suspensions

Yile Gu, Ali Ozel, Jari Kolehmainen, Sankaran Sundaresan

Research output: Contribution to journalArticle

Abstract

Developing constitutive models for particle phase rheology in gas-fluidized suspensions through rigorous statistical mechanical methods is very difficult when complex inter-particle forces are present. In the present study, we pursue a computational approach based on results obtained through Eulerian-Lagrangian simulations of the fluidized state. Simulations were performed in a periodic domain for non-cohesive and mildly cohesive (Geldart Group A) particles. Based on the simulation results, we propose modified closures for pressure, bulk viscosity, shear viscosity and the rate of dissipation of pseudo-thermal energy. For non-cohesive particles, results in the high granular temperature T regime agree well with constitutive expressions afforded by the kinetic theory of granular materials, demonstrating the validity of the methodology. The simulations reveal a low T regime, where the inter-particle collision time is determined by gravitational fall between collisions. Inter-particle cohesion has little effect in the high T regime, but changes the behaviour appreciably in the low T regime. At a given T, a cohesive particle system manifests a lower pressure at low particle volume fractions when compared to non-cohesive systems; at higher volume fractions, the cohesive assemblies attain higher coordination numbers than the non-cohesive systems, and experience greater pressures. Cohesive systems exhibit yield stress, which is weakened by particle agitation, as characterized by T. All these effects are captured through simple modifications to the kinetic theory of granular materials for non-cohesive materials.

LanguageEnglish (US)
Pages318-349
Number of pages32
JournalJournal of Fluid Mechanics
Volume860
DOIs
StatePublished - Feb 10 2019

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Constitutive models
Rheology
rheology
Kinetic theory
Granular materials
Volume fraction
Gases
gases
Shear viscosity
Thermal energy
Yield stress
granular materials
kinetic theory
Viscosity
simulation
viscosity
particle collisions
agitation
cohesion
coordination number

Cite this

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abstract = "Developing constitutive models for particle phase rheology in gas-fluidized suspensions through rigorous statistical mechanical methods is very difficult when complex inter-particle forces are present. In the present study, we pursue a computational approach based on results obtained through Eulerian-Lagrangian simulations of the fluidized state. Simulations were performed in a periodic domain for non-cohesive and mildly cohesive (Geldart Group A) particles. Based on the simulation results, we propose modified closures for pressure, bulk viscosity, shear viscosity and the rate of dissipation of pseudo-thermal energy. For non-cohesive particles, results in the high granular temperature T regime agree well with constitutive expressions afforded by the kinetic theory of granular materials, demonstrating the validity of the methodology. The simulations reveal a low T regime, where the inter-particle collision time is determined by gravitational fall between collisions. Inter-particle cohesion has little effect in the high T regime, but changes the behaviour appreciably in the low T regime. At a given T, a cohesive particle system manifests a lower pressure at low particle volume fractions when compared to non-cohesive systems; at higher volume fractions, the cohesive assemblies attain higher coordination numbers than the non-cohesive systems, and experience greater pressures. Cohesive systems exhibit yield stress, which is weakened by particle agitation, as characterized by T. All these effects are captured through simple modifications to the kinetic theory of granular materials for non-cohesive materials.",
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Computationally generated constitutive models for particle phase rheology in gas-fluidized suspensions. / Gu, Yile; Ozel, Ali; Kolehmainen, Jari; Sundaresan, Sankaran.

In: Journal of Fluid Mechanics, Vol. 860, 10.02.2019, p. 318-349.

Research output: Contribution to journalArticle

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