Magnetic field effects in the impact of a magnetic fluid drop

Sudo, Seiichi; Wakamatsu, Naoya; Ikohagi, Toshiaki; Nishiyama, Hideya; Ohaba, Motoyoshi; Katagiri, Kazunari

doi:10.1016/s0304-8853(99)00029-3

Cited by 10 publications

(10 citation statements)

References 4 publications

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“…Duvivier et al [7] used a magnet below a horizontal superhydrophobic substrate to modify the gravitational effects during droplet impact, and explored the different dynamics under different We, Bo m and Re. Sudo et al [8] studied the influence of the magnetic field strength on the maximum spreading diameter and the splashing dynamics. Spikes (albeit not similar to the Rosenswieg instability) were observed in the case of magnetic field perpendicular to the substrate, but not for the case of field parallel to the substrate.…”

Section: Introductionmentioning

confidence: 99%

Collisional ferrohydrodynamics of magnetic fluid droplets on superhydrophobic surfaces

et al. 2021

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The study reports the aspects of post-impact hydrodynamics of ferrofluid droplets on superhydrophobic (SH) surfaces in the presence of a horizontal magnetic field. A wide gamut of dynamics was observed by varying the impact Weber number (We), the Hartmann number (Ha) and the magnetic field strength (manifested through the magnetic Bond number (Bo m )). For a fixed We~60, we observed that at moderately low Bo m ~300, droplet rebound off the SH surface is suppressed. The noted We is chosen to observe various impact outcomes and to reveal the consequent ferrohydrodynamic mechanisms. We also show that ferrohydrodynamic interactions leads to asymmetric spreading; and the droplet spreads preferentially in a direction orthogonal to the magnetic field lines. We show analytically that during the retraction regime, the kinetic energy of the droplet is distributed unequally in the transverse and longitudinal directions due to the Lorentz force. This ultimately leads to suppression of droplet rebound. We study the role of Bo m at fixed We~60, and observed that the liquid lamella becomes unstable at the onset of retraction phase, through nucleation of holes, their proliferation and rupture after reaching a critical thickness only on SH surfaces, but is absent on hydrophilic surfaces. We propose an analytical model to predict the onset of instability at a critical Bo m . The analytical model shows that the critical Bo m is a function of the impact We, and the critical Bo m decreases with increasing We. We illustrate a phase map encompassing all the post-impact ferrohydrodynamic phenomena on SH surfaces for a wide range of We and Bo m .

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Section: Introductionmentioning

confidence: 99%

Collisional ferrohydrodynamics of magnetic fluid droplets on superhydrophobic surfaces

et al. 2021

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“…The maximum spreading of the droplet was proportional to the corresponding non-dimensional numbers, like Weber number (We), magnetic Bond number (Bo m ), and Reynolds number (Re). Sudo et al 6 explored the effect of the magnetic field on the maximum spreading diameter and spike formation within the liquid lamella of impacting magnetic fluid droplets. Rahimi and Weihs 7 reported the droplet impact dynamics of magnetorheological fluids and the dependence of the maximum spreading factor on the magnetic field strength and Reynolds number (Re).…”

Section: Introductionmentioning

confidence: 99%

Magneto-Elastic Effect in Non-Newtonian Ferrofluid Droplets Impacting Superhydrophobic Surfaces

2021

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In this article, we propose, with the aid of detailed experiments and scaling analysis, the existence of magneto-elastic effects in the impact hydrodynamics of non-Newtonian ferrofluid droplets on superhydrophobic surfaces in the presence of a magnetic field. The effects of magnetic Bond number (Bo m), Weber number (We), polymer concentration, and magnetic nanoparticle (Fe3O4) concentration in the ferrofluids were investigated. In comparison to Newtonian ferrofluid droplets, addition of polymers caused rebound suppression of the droplets relatively at lower Bo m for a fixed magnetic nanoparticle concentration and We. We further observed that for a fixed polymer concentration and We, increasing magnetic nanoparticle concentration also triggers earlier rebound suppression with increasing Bo m. In the absence of the magnetic nanoparticles, the non-Newtonian droplets do not show rebound suppression for the range of Bo m investigated. Likewise, the Newtonian ferrofluids show rebound suppression at large Bo m. This intriguing interplay of elastic effects of polymer chains and the magnetic nanoparticles, dubbed as the magneto-elastic effect, is noted to lead to the rebound suppression. We establish a scaling relationship to show that the rebound suppression is observed as a manifestation of the onset of magneto-elastic instability only when the proposed magnetic Weissenberg number (Wi m) exceeds unity. We also put forward a phase map to identify the various regimes of impact ferrohydrodynamics of such droplets and the occurrence of the magneto-elastic effect.

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“…The experimental method is similar to that presented by authors in our previous paper (Sudo et al, 1999). Figure 1 shows the experimental apparatus.…”

Section: Experimental Apparatus and Proceduresmentioning

confidence: 87%

“…Kim et al (2000) developed a linear perturbation theory to investigate the interface instabilities of a radially-expanding, liquid jet in cylindrical geometries when a liquid droplet impinges on a solid surface. Authors also studied the impact phenomena between a magnetic fluid drop and paper on the hard rubber mat, subject to magnetic field (Sudo et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Impact of Droplets of Magneto-Rheological Suspension Under Applied Magnetic Fields

Sudo

Funaoka²,

Nishiyama

2002

Journal of Intelligent Material Systems and Structures

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An experimental study is presented of the dynamic behavior of the impacting droplet of magneto-rheological suspension under applied magnetic fields. Effects of magnetic fields on the impact phenomena between a MR fluid droplet and paper on the hard rubber mat were revealed with a three-dimensional motion analysis system. In case of perpendicular magnetic field to a target surface, the MR fluid droplet did not collapse completely by its impact, but MR fluid spikes were formed by the magnetic field. In case of parallel magnetic field to a target surface, the MR fluid droplet showed complicated deformation. In case of strong parallel field, the MR fluid droplet showed breakup into few droplets.

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Magnetic field effects in the impact of a magnetic fluid drop

Cited by 10 publications

References 4 publications

Collisional ferrohydrodynamics of magnetic fluid droplets on superhydrophobic surfaces

Collisional ferrohydrodynamics of magnetic fluid droplets on superhydrophobic surfaces

Magneto-Elastic Effect in Non-Newtonian Ferrofluid Droplets Impacting Superhydrophobic Surfaces

Impact of Droplets of Magneto-Rheological Suspension Under Applied Magnetic Fields

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