### Abstract

In a fluidized bed, the drag force acts to oppose the downward force of gravity on a particle, and thus provides the main mechanism for fluidization. Drag models that are employed in large-scale simulations of fluidized beds are typically based on either fixed particle beds or the sedimentation of particles in liquids. In low-Reynolds-number (Re) systems, these two types of fluidized beds represent the limits of high Stokes number (Si) and low Si, respectively. In this work, the fluid particle drag behaviour of these two regimes is bridged by investigating the effect of Si on the drag force in low-Re systems. This study is conducted using fully resolved lattice Boltzmann simulations of a system composed of fluid and monodisperse spherical particles. In these simulations, the particles are free to translate and rotate based on the effects of the surrounding fluid. Through this work, three distinct regimes in the characteristics of the fluid particle drag force are observed: low, intermediate and high Si. It is found that, in the low-Re regime, a decrease in Si results in a reduction in the fluid particle drag. Based on the simulation results, a new drag relation is proposed, which is, unlike previous models, dependent on St.

Original language | English |
---|---|

Pages (from-to) | 576-601 |

Number of pages | 26 |

Journal | Journal of Fluid Mechanics |

Volume | 788 |

Early online date | 8 Jan 2016 |

DOIs | |

Publication status | Published - Feb 2016 |

### Keywords

- fluidized beds
- particle/fluid flow
- suspensions
- numerical simulations
- bidisperse arrays
- equation
- sedimentation
- monodisperse
- bed
- boundary
- dynamics
- automata

### Cite this

*Journal of Fluid Mechanics*,

*788*, 576-601. https://doi.org/10.1017/jfm.2015.679

**Lattice Boltzmann simulations of low-Reynolds-number flow past fluidized spheres : effect of Stokes number on drag force.** / Rubinstein, Gregory J.; Derksen, J. J.; Sundaresan, Sankaran.

Research output: Contribution to journal › Article

*Journal of Fluid Mechanics*, vol. 788, pp. 576-601. https://doi.org/10.1017/jfm.2015.679

}

TY - JOUR

T1 - Lattice Boltzmann simulations of low-Reynolds-number flow past fluidized spheres

T2 - effect of Stokes number on drag force

AU - Rubinstein, Gregory J.

AU - Derksen, J. J.

AU - Sundaresan, Sankaran

PY - 2016/2

Y1 - 2016/2

N2 - In a fluidized bed, the drag force acts to oppose the downward force of gravity on a particle, and thus provides the main mechanism for fluidization. Drag models that are employed in large-scale simulations of fluidized beds are typically based on either fixed particle beds or the sedimentation of particles in liquids. In low-Reynolds-number (Re) systems, these two types of fluidized beds represent the limits of high Stokes number (Si) and low Si, respectively. In this work, the fluid particle drag behaviour of these two regimes is bridged by investigating the effect of Si on the drag force in low-Re systems. This study is conducted using fully resolved lattice Boltzmann simulations of a system composed of fluid and monodisperse spherical particles. In these simulations, the particles are free to translate and rotate based on the effects of the surrounding fluid. Through this work, three distinct regimes in the characteristics of the fluid particle drag force are observed: low, intermediate and high Si. It is found that, in the low-Re regime, a decrease in Si results in a reduction in the fluid particle drag. Based on the simulation results, a new drag relation is proposed, which is, unlike previous models, dependent on St.

AB - In a fluidized bed, the drag force acts to oppose the downward force of gravity on a particle, and thus provides the main mechanism for fluidization. Drag models that are employed in large-scale simulations of fluidized beds are typically based on either fixed particle beds or the sedimentation of particles in liquids. In low-Reynolds-number (Re) systems, these two types of fluidized beds represent the limits of high Stokes number (Si) and low Si, respectively. In this work, the fluid particle drag behaviour of these two regimes is bridged by investigating the effect of Si on the drag force in low-Re systems. This study is conducted using fully resolved lattice Boltzmann simulations of a system composed of fluid and monodisperse spherical particles. In these simulations, the particles are free to translate and rotate based on the effects of the surrounding fluid. Through this work, three distinct regimes in the characteristics of the fluid particle drag force are observed: low, intermediate and high Si. It is found that, in the low-Re regime, a decrease in Si results in a reduction in the fluid particle drag. Based on the simulation results, a new drag relation is proposed, which is, unlike previous models, dependent on St.

KW - fluidized beds

KW - particle/fluid flow

KW - suspensions

KW - numerical simulations

KW - bidisperse arrays

KW - equation

KW - sedimentation

KW - monodisperse

KW - bed

KW - boundary

KW - dynamics

KW - automata

U2 - 10.1017/jfm.2015.679

DO - 10.1017/jfm.2015.679

M3 - Article

VL - 788

SP - 576

EP - 601

JO - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

SN - 0022-1120

ER -