Numerical simulations of the rheology of suspensions of rigid spheres at low volume fraction in a viscoelastic fluid under shear

Yang, Mo; Krishnan, Sreenath; Shaqfeh, Eric S. G.

doi:10.1016/j.jnnfm.2016.04.003

Cited by 26 publications

(49 citation statements)

References 31 publications

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“…where the symbol <> indicates that the quantity has been averaged in the two homogeneous directions and in time. Following Yang et al (2016), it can be shown that the wall normal velocity gradients at the wall is equivalent to the bulk shear stress. Here, we show how to include the interfacial tension contribution inside the shear stress balance.…”

Section: Resultsmentioning

confidence: 99%

“…The wall-normal gradient of the streamwise velocity gradient at the walls can be used to evaluate the effective viscosity of an emulsion as where the symbol indicates that the quantity has been averaged in the two homogeneous directions and in time. Following Yang, Krishnan & Shaqfeh (2016), it can be shown that the wall-normal velocity gradient at the wall is equivalent to the bulk shear stress. Here, we show how to include the interfacial tension contribution inside the shear stress balance.…”

Section: Resultsmentioning

confidence: 99%

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On the effect of coalescence on the rheology of emulsions

et al. 2019

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We present a numerical study of the rheology of a two-fluid emulsion in dilute and semidilute conditions. The analysis is performed for different capillary numbers, volume fraction and viscosity ratio under the assumption of negligible inertia and zero buoyancy force. The effective viscosity of the system increases for low values of the volume fraction and decreases for higher values, with a maximum for about 20% concentration of the disperse phase. When the dispersed fluid has lower viscosity, the normalised effective viscosity becomes smaller than 1 for high enough volume fractions. To single out the effect of droplet coalescence on the rheology of the emulsion we introduce an Eulerian force which prevents merging, effectively modelling the presence of surfactants in the system. When the coalescence is inhibited the effective viscosity is always greater than 1 and the curvature of the function representing the emulsion effective viscosity vs. the volume fraction becomes positive, resembling the behaviour of suspensions of deformable particles. The reduction of the effective viscosity in the presence of coalescence is associated to the reduction of the total surface of the disperse phase when the droplets merge, which leads to a reduction of the interface tension contribution to the total shear stress. The probability density function of the flow topology parameter shows that the flow is mostly a shear flow in the matrix phase, with regions of extensional flow when the coalescence is prohibited. The flow in the disperse phase, instead, always shows rotational components. The first normal stress difference is positive, except for the smallest viscosity ratio considered, whereas the second normal difference is negative, with their ratio being constant with the volume fraction. Our results clearly show that the coalescence efficiency strongly affects the system rheology and neglecting droplet merging can lead to erroneous predictions. † Email address for correspondence: fdv@mech.kth.se

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

On the effect of coalescence on the rheology of emulsions

et al. 2019

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“…Further details of the method described thus far, including extensive validation studies and comparison with experiments, can be found in previously published works (Richter, Iaccarino & Shaqfeh 2010; Padhy etal. 2013; Yang, Krishnan & Shaqfeh 2016; Castillo etal. 2019).…”

Section: Solution Methodologymentioning

confidence: 99%

Swimming with swirl in a viscoelastic fluid

et al. 2020

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“…The governing equations and boundary conditions are solved using a third-order -accurate finite volume flow solver developed in a series of previous publications (Ham, Mattsson & Iaccarino 2006; Richter, Iaccarino & Shaqfeh 2010; Padhy et al. 2013; Yang, Krishnan & Shaqfeh 2016; Castillo et al. 2019; Binagia et al.…”

Section: Approximate Solutionsmentioning

confidence: 99%