Effects of confinement-induced non-Newtonian lubrication forces on the rheology of a dense suspension
Por:
Rosales-Romero A., Vázquez-Quesada A., Prasanna Kumar S.S., López-Aguilar J.E., Ellero M.
Publicada:
1 ene 2024
Ahead of Print:
1 may 2024
Resumen:
In this work, we propose a functionalised bi-viscous lubrication model to study the material properties of concentrated non-Brownian suspensions and explore the possible confinement-induced non-Newtonian effects of the lubricant in the rheological response of this type of suspensions. From tribological studies, it is well-known that even macroscopically Newtonian liquids under strong confinement might exhibit properties which deviate significantly from their bulk behaviour. When two surfaces separated by an extremely small gap (still large compared to the molecular size) are sheared, strong shear-thinning of the lubricant viscosity at low shear-rates is observed, in spite of its Newtonian-like bulk response. This is connected to a significant increase of the zero-shear-rate viscosity under extreme confinement. We start from an effective lubrication algorithm recently proposed and develop a new gap-size-dependent interparticle bi-viscous lubrication model, able to capture qualitatively the main phenomenology of confined lubricants. We solve the lubrication interaction between particles iteratively via a semi-implicit splitting scheme. Since the handling of lubrication is made implicitly here, the method copes efficiently with large increases of the inter-particle effective viscosities, which would otherwise lead to simulation blow-up or the use of vanishing time-steps in standard explicit schemes. We analyse the rheological response of the suspension systematically in terms of model parameters. In contrast to pure Newtonian lubrication interactions, distinct shear-thinning and shear-thickening regimes in the relative suspension viscosity are observed, which are discussed in terms of particle microstructure coupled with the complex rheology of the confined lubricant. In addition, normal-stress response is negative in both N1 and N2, which is difficult to achieve with standard contact frictional models. © 2024 Elsevier B.V.
Filiaciones:
Rosales-Romero A.:
Facultad de Química, Departamento de Ingeniería Química, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, Coyoacán, Ciudad de México, 04510, Mexico
Vázquez-Quesada A.:
Departamento de Física Fundamental, UNED, Apartado 60141, Madrid, 28080, Spain
Prasanna Kumar S.S.:
Basque Center for Applied Mathematics (BCAM), Alameda de Mazarredo 14, Bilbao, 48009, Spain
López-Aguilar J.E.:
Facultad de Química, Departamento de Ingeniería Química, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, Coyoacán, Ciudad de México, 04510, Mexico
Ellero M.:
Basque Center for Applied Mathematics (BCAM), Alameda de Mazarredo 14, Bilbao, 48009, Spain
IKERBASQUE, Basque Foundation for Science, Calle de María Díaz de Haro 3, Bilbao, 48013, Spain
Zienkiewicz Centre for Computational Engineering (ZCCE), Swansea University, Bay Campus, Swansea, SA1 8EN, United Kingdom
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