### Abstract

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

Pages (from-to) | 83-94 |

Number of pages | 12 |

Journal | Journal of Non-Newtonian Fluid Mechanics |

Volume | 235 |

Early online date | 26 Jul 2016 |

DOIs | |

Publication status | E-pub ahead of print - 26 Jul 2016 |

### Fingerprint

### Keywords

- particle settling
- suspensions
- deposits
- shear thinning
- viscoplastic
- shear flows
- dynamic settling
- non-Newtonian fluids
- settling velocity

### Cite this

*Journal of Non-Newtonian Fluid Mechanics*,

*235*, 83-94. https://doi.org/10.1016/j.jnnfm.2016.07.011

}

*Journal of Non-Newtonian Fluid Mechanics*, vol. 235, pp. 83-94. https://doi.org/10.1016/j.jnnfm.2016.07.011

**Dynamic settling of particles in shear flows of shear-thinning fluids.** / Childs, L. H.; Hogg, A. J.; Pritchard, D.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Dynamic settling of particles in shear flows of shear-thinning fluids

AU - Childs, L. H.

AU - Hogg, A. J.

AU - Pritchard, D.

PY - 2016/7/26

Y1 - 2016/7/26

N2 - Dynamic settling is the phenomenon whereby a relatively dense particle settles through a sheared flow of a non-Newtonian fluid at a speed that depends on the shear rate of the background flow. This means that due to the non-linear rheology, the settling velocity may vary spatially and temporally as the background shear rate of the suspending fluid varies, an effect which does not occur in Newtonian fluids. In this contribution, the consequences of this dependency are explored for a dilute suspension of particles released uniformly from a source in a sustained and externally-driven flow of shear-thinning fluid. It is shown theoretically that the concentration field does not remain uniform, but evolves downstream, allowing calculation of the runout length, settling times and distribution of the deposited particles. Flows with a velocity maximum are demonstrated to affect the concentration field very strongly as they develop a ‘kinematic barrier’ over which settling times are considerably lengthened. Flows with bidisperse suspensions are shown to produce deposits that vary non-monotonically in thickness and composition with distance downstream, an effect which is solely due to dynamic settling. Finally flows of viscoplastic fluids which exhibit yielded and unyielded regions may accentuate the role and effects of the kinematic barrier to settling.

AB - Dynamic settling is the phenomenon whereby a relatively dense particle settles through a sheared flow of a non-Newtonian fluid at a speed that depends on the shear rate of the background flow. This means that due to the non-linear rheology, the settling velocity may vary spatially and temporally as the background shear rate of the suspending fluid varies, an effect which does not occur in Newtonian fluids. In this contribution, the consequences of this dependency are explored for a dilute suspension of particles released uniformly from a source in a sustained and externally-driven flow of shear-thinning fluid. It is shown theoretically that the concentration field does not remain uniform, but evolves downstream, allowing calculation of the runout length, settling times and distribution of the deposited particles. Flows with a velocity maximum are demonstrated to affect the concentration field very strongly as they develop a ‘kinematic barrier’ over which settling times are considerably lengthened. Flows with bidisperse suspensions are shown to produce deposits that vary non-monotonically in thickness and composition with distance downstream, an effect which is solely due to dynamic settling. Finally flows of viscoplastic fluids which exhibit yielded and unyielded regions may accentuate the role and effects of the kinematic barrier to settling.

KW - particle settling

KW - suspensions

KW - deposits

KW - shear thinning

KW - viscoplastic

KW - shear flows

KW - dynamic settling

KW - non-Newtonian fluids

KW - settling velocity

U2 - 10.1016/j.jnnfm.2016.07.011

DO - 10.1016/j.jnnfm.2016.07.011

M3 - Article

VL - 235

SP - 83

EP - 94

JO - Journal of Non-Newtonian Fluid Mechanics

JF - Journal of Non-Newtonian Fluid Mechanics

SN - 0377-0257

ER -