Using short-ranged repulsion to tune suspension viscosity and shear thickening

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Dense suspensions of solid particles exhibit rich and fascinating flow behaviour. Models and numerical simulations play an important role in understanding the mechanisms as well as exploring parameter space. Working with a recently established framework [1], where suspension viscosity is controlled by forming frictional contacts, we investigate how particle contact properties change suspension rheology. In particular, we use discrete element methods (DEM) to investigate the effects that adding short-ranged pairwise particle repulsive interactions has on the rheology of these granular dense suspensions [2]. Recent experiments using charge-stabilised particles suggest that increasing short-ranged particle-particle repulsion results in an increase in onset stress.

Our work using DEM simulations corroborates these findings, and attributes the observed increase in onset stress solely to increases in the peak force of the short-ranged repulsion. Other factors, such as charge-screening lengths, were found to have little to no effect on the onset stress. Furthermore, we show that the onset stress is linearly correlated with the peak repulsive force and that this linear correlation holds regardless of the repulsive force profile used. Lastly, the linear correlation observed in simulations matches experimental results perfectly. Currently, we are researching the effects that adding short-range particle attractions and particle adhesion (resistance to rolling) has on suspension shear rheology.

References

[1]M. Wyart and M. E. Cates. Discontinuous shear thickening without inertia in dense nonbrownian suspensions. Phys. Rev. Lett., 112:098302, 2014.
[2]N. Y. C. Lin, B. M. Guy, M. Hermes, C. Ness, J. Sun, W. C. K. Poon, and I. Cohen. Hydrodynamic and contact contributions to continuous shear thickening in colloidal suspensions. Phys. Rev. Lett., 115:228304, Nov 2015.

The onset stress of shear thickening increases as the peak repulsive force increases. These results are from simulations of suspensions of frictional granular particles with shortranged, DLVO-style repulsive forces.
The onset stress of shear thickening increases as the peak repulsive force increases. These results are from simulations of suspensions of frictional granular particles with shortranged, DLVO-style repulsive forces.
The onset stress as a function of peak repulsive force from simulations (left) and experiment (right). The black line of best fit, derived from simulation, follows the linear equation: onset stress = 0.4*peak force. The inset (right) shows the normalised repulsive force profiles used as functions of pairwise particle-particle separation. The three simulation force profiles used are: DLVO (black), linear slope (blue), and linear block (red).
The onset stress as a function of peak repulsive force from simulations (left) and experiment (right). The black line of best fit, derived from simulation, follows the linear equation: onset stress = 0.4*peak force. The inset (right) shows the normalised repulsive force profiles used as functions of pairwise particle-particle separation. The three simulation force profiles used are: DLVO (black), linear slope (blue), and linear block (red).

Principal Investigator: 

Postgraduate Researchers: 

Research Institutes: 

  • Infrastructure and Environment

Research Themes: 

  • Granular Mechanics and Industrial Infrastructure

Last modified: 

Friday, September 14, 2018 - 18:02

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