Deformation of a ferrofluid droplet in a simple shear flow under the effect of a constant magnetic field

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Abstract: In the present work, we investigate the dynamics of a droplet of ferrofluid placed in a shear flow field subjected to the additional action produced by the application of a magnetic field in a direction perpendicular to the flow. The problem is solved in the framework of a moving-boundary method based on the solution of the Navier-Stokes equations complemented with the additional equations required for the determination of the magnetic force. The results reveal interesting changes in the trends displayed by the droplet deformation and inclination angle as a function of the capillary number when the intensity of the magnetic field is varied while maintaining flow conditions corresponding to the Stokes regime. The mechanism of droplet relaxation from equilibrium when the magnetic force is suddenly removed is also investigated. According to our numerical experiments the deformation evolves in time following a harmonic decaying process, which, in the limit of small capillary number, i.e. for very small deformations, can be fairly well represented by the temporal evolution of a simple damped harmonic oscillator.
LanguageEnglish
Pages313-323
Number of pages11
JournalComputers and Fluids
Volume173
Early online date2 Jul 2018
DOIs
Publication statusPublished - 15 Sep 2018

Fingerprint

Magnetic fluids
Shear flow
Magnetic fields
Navier Stokes equations
Flow fields
Experiments

Keywords

  • ferrofluid
  • dilute emulsions
  • level set-volume of fluid
  • droplet deformation

Cite this

@article{2c60867de25b40e891015884b75dfc3e,
title = "Deformation of a ferrofluid droplet in a simple shear flow under the effect of a constant magnetic field",
abstract = "Abstract: In the present work, we investigate the dynamics of a droplet of ferrofluid placed in a shear flow field subjected to the additional action produced by the application of a magnetic field in a direction perpendicular to the flow. The problem is solved in the framework of a moving-boundary method based on the solution of the Navier-Stokes equations complemented with the additional equations required for the determination of the magnetic force. The results reveal interesting changes in the trends displayed by the droplet deformation and inclination angle as a function of the capillary number when the intensity of the magnetic field is varied while maintaining flow conditions corresponding to the Stokes regime. The mechanism of droplet relaxation from equilibrium when the magnetic force is suddenly removed is also investigated. According to our numerical experiments the deformation evolves in time following a harmonic decaying process, which, in the limit of small capillary number, i.e. for very small deformations, can be fairly well represented by the temporal evolution of a simple damped harmonic oscillator.",
keywords = "ferrofluid, dilute emulsions, level set-volume of fluid, droplet deformation",
author = "Paolo Capobianchi and Marcello Lappa and Oliveira, {M{\'o}nica S. N.}",
year = "2018",
month = "9",
day = "15",
doi = "10.1016/j.compfluid.2018.06.024",
language = "English",
volume = "173",
pages = "313--323",
journal = "Computers and Fluids",
issn = "0045-7930",

}

TY - JOUR

T1 - Deformation of a ferrofluid droplet in a simple shear flow under the effect of a constant magnetic field

AU - Capobianchi, Paolo

AU - Lappa, Marcello

AU - Oliveira, Mónica S. N.

PY - 2018/9/15

Y1 - 2018/9/15

N2 - Abstract: In the present work, we investigate the dynamics of a droplet of ferrofluid placed in a shear flow field subjected to the additional action produced by the application of a magnetic field in a direction perpendicular to the flow. The problem is solved in the framework of a moving-boundary method based on the solution of the Navier-Stokes equations complemented with the additional equations required for the determination of the magnetic force. The results reveal interesting changes in the trends displayed by the droplet deformation and inclination angle as a function of the capillary number when the intensity of the magnetic field is varied while maintaining flow conditions corresponding to the Stokes regime. The mechanism of droplet relaxation from equilibrium when the magnetic force is suddenly removed is also investigated. According to our numerical experiments the deformation evolves in time following a harmonic decaying process, which, in the limit of small capillary number, i.e. for very small deformations, can be fairly well represented by the temporal evolution of a simple damped harmonic oscillator.

AB - Abstract: In the present work, we investigate the dynamics of a droplet of ferrofluid placed in a shear flow field subjected to the additional action produced by the application of a magnetic field in a direction perpendicular to the flow. The problem is solved in the framework of a moving-boundary method based on the solution of the Navier-Stokes equations complemented with the additional equations required for the determination of the magnetic force. The results reveal interesting changes in the trends displayed by the droplet deformation and inclination angle as a function of the capillary number when the intensity of the magnetic field is varied while maintaining flow conditions corresponding to the Stokes regime. The mechanism of droplet relaxation from equilibrium when the magnetic force is suddenly removed is also investigated. According to our numerical experiments the deformation evolves in time following a harmonic decaying process, which, in the limit of small capillary number, i.e. for very small deformations, can be fairly well represented by the temporal evolution of a simple damped harmonic oscillator.

KW - ferrofluid

KW - dilute emulsions

KW - level set-volume of fluid

KW - droplet deformation

UR - https://www.sciencedirect.com/journal/computers-and-fluids

U2 - 10.1016/j.compfluid.2018.06.024

DO - 10.1016/j.compfluid.2018.06.024

M3 - Article

VL - 173

SP - 313

EP - 323

JO - Computers and Fluids

T2 - Computers and Fluids

JF - Computers and Fluids

SN - 0045-7930

ER -