Shear rheology of a dilute emulsion of ferrofluid droplets dispersed in a nonmagnetizable carrier fluid under the influence of a uniform magnetic field

• Tipo: Artigo em Revista Científica Internacional
• Data: 2021

Autores

P. Capobianchi (Autor) Outra; M. Lappa (Autor) Outra; M. S. N. Oliveira (Autor) Outra; F. T. Pinho (Autor) FEUP

Revista

Título: Journal of Rheology

Vol. 65

Páginas: 925-941

ISSN: 0148-6055

Editora: Society of Rheology

Indexação

ISI Web of Knowledge - 0 Citações

Scopus - 6 Citações

Outras Informações

ID Authenticus: P-00V-5QS

DOI: 10.1122/8.0000226

Abstract (EN): The effect of a spatially uniform magnetic field on the shear rheology of a dilute emulsion of monodispersed ferrofluid droplets, immersed in a nonmagnetizable immiscible fluid, is investigated using direct numerical simulations. The direction of the applied magnetic field is normal to the shear flow direction. The droplets' extra-stress tensor arising from the presence of interfacial forces of magnetic nature is modeled on the basis of the seminal work of G. K. Batchelor [J. Fluid Mech. 41, 545-570 (1970)] under the assumptions of a linearly magnetizable ferrofluid phase and negligible inertia. The results show that even relatively small magnetic fields can have significant consequences on the rheological properties of the emulsion due to the magnetic forces that contribute to deform and orient the droplets toward the direction of the applied magnetic vector. In particular, we have observed an increase in the effective (bulk) viscosity and a reversal of the sign of the two normal stress differences with respect to the case without magnetic field for those conditions where the magnetic force prevails over the shearing force. Comparisons between the results of our model with a direct integration of the viscous stress have provided an indication of its reliability to predict the effective viscosity of the suspension. Moreover, this latter quantity has been found to behave as a monotonic increasing function of the applied magnetic field for constant shearing flows ("magneto-thickening" behavior), which allowed us to infer a simple constitutive equation describing the emulsion viscosity.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 17