Effect of viscosity contrast on the dynamics of a sheared lamellar mesophase

Pal, A. and Jaju, S.J. and Kumaran, V. (2023) Effect of viscosity contrast on the dynamics of a sheared lamellar mesophase. In: Journal of Non-Newtonian Fluid Mechanics, 320 .

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Abstract

A mesoscale continuum model is used to examine the relation between structure and dynamics of a sheared lamellar phase, with specific attention to the role of the contrast in viscosity between the hydrophilic and hydrophobic components. The structure and rheology is analysed as a function of the Ericksen number, the ratio of the viscous stress and the layer compression modulus, the parameter ScΣ, and a viscosity contrast parameter which is the ratio of the viscosities of the hydrophobic and hydrophobic parts. Here, the Schmidt number Sc is the ratio of momentum and mass diffusivity, Σ is the dimensionless ratio of elastic and viscous stresses in the absence of flow. For relatively high Ericksen number, where the viscous stress is much larger than the stress due to concentration variation, viscosity contrast does not have a significant effect on the structure and rheology. Shear tends to align the layers in the �perpendicular� direction with concentration modulation perpendicular to the flow plane, but defects persist even after shearing for hundreds of strain units. For relatively low Ericksen number, an increase in the viscosity contrast alters the direction of ordering at low ScΣ. Whereas the concentration modulation is perpendicular to the flow plane when there is no viscosity contrast, the layers are aligned along the �parallel� direction with modulation is along the velocity gradient for high viscosity contrast. In contrast, the alignment is in the perpendicular direction for high ScΣ. The apparent viscosity could exceed that of the ordered state by up to an order of magnitude at low Ericksen number. © 2023 Elsevier B.V.

Item Type:	Journal Article
Publication:	Journal of Non-Newtonian Fluid Mechanics
Publisher:	Elsevier B.V.
Additional Information:	The Copyright for this articles belongs to the Elsevier B.V.
Keywords:	Continuum mechanics; Elasticity; Hydrophobicity; Shear flow; Viscous flow, Continuum model; Ericksen number; Hydrophobics; Lamellar mesophases; Lamellar phasis; Meso scale; Mesoscale simulation; Structure and dynamics; Viscosity contrast; Viscous stress, Viscosity
Department/Centre:	Division of Mechanical Sciences > Chemical Engineering
Date Deposited:	09 Nov 2023 11:00
Last Modified:	09 Nov 2023 11:00
URI:	https://eprints.iisc.ac.in/id/eprint/83312

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