Vertical magnetic field aided droplet-impact- magnetohydrodynamics of ferrofluids

Sahoo, Nilamani; Dhar, Purbarun; Samanta, Devranjan

doi:10.1016/j.colsurfa.2021.127872

Cited by 12 publications

(7 citation statements)

References 29 publications

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“…A loss of peak height in spreading ferrofluid drops has previously been attributed to a reduction in vertical magnetic flux density, 12 but here the loss in height is likely to be due to increased magnetic field gradient and stabilisation of the rim due to the radial field component. Rim formation in a ferrofluid droplet has been observed previously, 25 but this occurred in a uniform vertical magnetic field created by electromagnetic coils, and the rim was not pinned as in the present experiments.…”

Section: Rim Formationsupporting

confidence: 63%

“…We have also found that at relatively high magnetic flux densities, ferrofluid drop impacts can result in stationary rims of ferrofluid forming near the edge of the magnet. Rim formations have been observed previously, 25 although they were not stationary, likely due to weaker magnetic fields.…”

Section: Introductionsupporting

confidence: 50%

“…24 Drop impacts on solid surfaces for any fluid produce a spreading thin lamella, with a raised dynamic rim at the edge of the spreading droplet. 25 So-called 'crown' instabilities on this rim can lead to corona splashes, where secondary droplets are created. 18,26 For ferrofluids, we are particularly interested in the interplay between the formation of crown instabilities and Rosensweig instabilities, as well as the patterning of these instabilities.…”

Section: Introductionmentioning

confidence: 99%

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Ferrofluid drop impacts and Rosensweig peak formation in a non-uniform magnetic field

et al. 2023

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Section: Rim Formationsupporting

confidence: 63%

Section: Introductionsupporting

confidence: 50%

Section: Introductionmentioning

confidence: 99%

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Ferrofluid drop impacts and Rosensweig peak formation in a non-uniform magnetic field

et al. 2023

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“…Ferrofluid has demonstrated a wide range of studies, including encapsulation, mixing, droplet manipulation, evaporation, and cell sorting . The impact dynamics of magnetic droplets on a nonmagnetic substrate is widely studied in the literature, which involves the effect of magnetic field on the dynamics of droplet spreading and postimpact self-assembly. − In this regard, Shyam et al have studied the impact dynamics of a water-based ferrofluid on PDMS substrate. It is found that upon impact, the ferrofluid droplet undergoes Rosensweig instability and exhibits several regimes of equilibrium configurations .…”

Section: Introductionmentioning

confidence: 99%

Magnetic Control of Water Droplet Impact onto Ferrofluid Lubricated Surfaces

2023

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Controlling the impact process of a droplet impacting a liquid film has remained a wide-open challenge. The existing passive techniques lack precise on-demand control of the impact dynamics of droplets. The present study introduces a magnet-assisted approach to control water droplets’ impact dynamics. We show that by incorporating a thin, magnetically active ferrofluid film, the overall droplet impact phenomena of the water droplets could be controlled. It is found that by modifying the distribution of the magnetic nanoparticles (MNPs) present inside the ferrofluid using a permanent magnet, the spreading and retraction behavior of the droplet could be significantly controlled. In addition to that, we also show that by altering the impact Weber number (We i), and the magnetic Bond number (Bo m), the outcomes of droplet impact could be precisely controlled. We reveal the role of the various forces on the consequential effects of droplet impact with the help of phase maps. Without the magnetic field, we discovered that the droplet impact on ferrofluid film results in no-splitting, jetting, and splashing regimes. On the other hand, the presence of magnetic field results in the no-splitting and jetting regime. However, beyond a critical magnetic field, the ferrofluid film gets transformed into an assembly of spikes. In such scenarios, the droplet impact only results in no-splitting and splashing regimes, while the jetting regime remains absent. The outcome of our study may find potential applications in chemical engineering, material synthesis, and three-dimensional (3D) printing where the control and optimization of the droplet impact process are desirable.

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“…Rahimi et al and Ahmed et al also experimentally studied the effects of magnetic field strength on the maximum spreading of a ferrofluid droplet, and Ahmed et al developed a theoretical model to predict the maximum spreading diameter based on the energy conservation principle. Besides the magnetic field strength, Zhou et al and Sahoo et al investigated the effects of the Fe 3 O 4 nanoparticle concentration and surface wettability on droplet magnetohydrodynamics. As the magnetic field provides additional driving forces for the droplet, the wetting behavior of the ferrofluid droplet is also affected, which has been investigated by Manukyan et al and Ahmed et al When placing a static ferrofluid droplet in a strong-enough magnetic field, it would split into daughter droplets and show the self-assembly phenomenon .…”

Section: Introductionmentioning

confidence: 99%

Magnetic Field-Assisted Fission of a Ferrofluid Droplet for Large-Scale Droplet Generation

et al. 2022

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With the presence of an external magnetic field, a ferrofluid droplet exhibits a rich variety of interesting phenomena notably different from nonmagnetic droplets. Here, a ferrofluid droplet impacting on a liquidrepellent surface is systematically investigated using high-speed imaging. The pre-and post-impact, including the droplet stretching, maximum spreading diameter, and final impact modes, are shown to depend on the impact velocity and the magnitude of the external magnetic field. A scaling relation involving the Weber and magnetic Bond numbers is fitted to predict the maximum spreading diameter based on the magnetic field-induced effective surface tension. The impact outcome is also investigated and classified into three patterns depending on the occurrence of the rim interface instability and the fission phenomenon. Two types of fission (i.e., evenly and unevenly distributed sizes of the daughter droplets) are first identified, and the corresponding mechanism is revealed. Last, according to Rayleigh−Taylor instability, a semiempirical formula is proposed to estimate the number of the daughter droplets in the regime of evenly distributed size, which agrees well with the experimental data. The present study can provide more insight into large-scale droplet generation with monodispersive sizes.

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Vertical magnetic field aided droplet-impact- magnetohydrodynamics of ferrofluids

Cited by 12 publications

References 29 publications

Ferrofluid drop impacts and Rosensweig peak formation in a non-uniform magnetic field

Ferrofluid drop impacts and Rosensweig peak formation in a non-uniform magnetic field

Magnetic Control of Water Droplet Impact onto Ferrofluid Lubricated Surfaces

Magnetic Field-Assisted Fission of a Ferrofluid Droplet for Large-Scale Droplet Generation

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