title: Interfacial patterns in magnetorheological fluids: Azimuthal field-induced structures.
abstract: Despite their practical and academic relevance, studies of interfacial pattern formation in confined magnetorheological (MR) fluids have been largely overlooked in the literature. In this work, we present a contribution to this soft matter research topic and investigate the emergence of interfacial instabilities when an inviscid, initially circular bubble of a Newtonian fluid is surrounded by a MR fluid in a Hele-Shaw cell apparatus. An externally applied, in-plane azimuthal magnetic field produced by a current-carrying wire induces interfacial disturbances at the two-fluid interface, and pattern-forming structures arise. Linear stability analysis, weakly nonlinear theory, and a vortex sheet approach are used to access early linear and intermediate nonlinear time regimes, as well as to determine stationary interfacial shapes at fully nonlinear stages.
authors.affiliation: Departamento de Física, Universidade Federal de Pernambuco, Recife, Pernambuco 50670-901 Brazil.
authors.forename: Eduardo O
authors.initials: EO
authors.lastname: Dias
authors.affiliation: Instituto de Física, Universidade Federal de Alagoas, Maceió, Alagoas 57072-900 Brazil.
authors.forename: Sérgio A
authors.initials: SA
authors.lastname: Lira
authors.affiliation: Departamento de Física, Universidade Federal de Pernambuco, Recife, Pernambuco 50670-901 Brazil.
authors.forename: José A
authors.initials: JA
authors.lastname: Miranda