Microscopic relationship between colloid-colloid interactions and the rheological behaviour of suspensions: a molecular dynamics-stochastic rotation dynamics investigation

We investigate the dependence of the shear viscosity of suspensions of spherical colloids as a function of the volume fraction of the suspension, the colloid-colloid interactions and the shear rate. We couple molecular dynamics to describe the motion of the colloids with stochastic rotation dynamics...

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Bibliographic Details
Published in:Molecular physics 2018-08, Vol.116 (15-16), p.2032-2040
Main Authors: Olarte-Plata, Juan D., Bresme, Fernando
Format: Article
Language:English
Subjects:
Colloids
Computational fluid dynamics
Computer simulation
Dependence
Fluid flow
Hydrodynamics
Molecular chains
Molecular dynamics
non-equilibrium molecular dynamics
Rheological properties
Rheology
Rotation
Shear rate
shear thickening
Shear thickening (liquids)
shear thinning
Shear thinning (liquids)
Shear viscosity
Softness
stochastic rotation dynamics
Thickening
Velocity gradient
Viscosity
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Summary:We investigate the dependence of the shear viscosity of suspensions of spherical colloids as a function of the volume fraction of the suspension, the colloid-colloid interactions and the shear rate. We couple molecular dynamics to describe the motion of the colloids with stochastic rotation dynamics (MD-SRD) for the fluid environment by means of stochastic collisions, in order to incorporate hydrodynamics effects leading to non-newtonian responses. The shear viscosity is computed using non-equilibrium simulations by imposing explicit velocity gradients. The impact of the colloid-colloid interactions is examined by modelling the inter-colloid pair potential with a repulsive power law, that allows interpolating different degrees of colloidal softness. The general rheological behaviour of our suspensions can be described with a Krieger-Dougherty like equation, which must be corrected to account for the variations in the maximum packing fraction and non-equilibrium effects arising from the flux of momentum imposed to the suspension, which appear when varying the softness of the inter-colloidal interactions. We further show evidence for non-newtonian behaviour at high Péclet numbers, characterised both by shear thinning and shear thickening, and thus demonstrate these effects can be successfully captured using MD-SRD methods.
ISSN:0026-8976
1362-3028
DOI:10.1080/00268976.2018.1464673