Elongational flow effects on the vortex growth out of Couette flow in ferrofluids

Altmeyer, Sebastian; Leschhorn, A.; Hoffmann, Christian; Lücke, M.

doi:10.1103/physreve.87.053010

Cited by 12 publications

(11 citation statements)

References 31 publications

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“…However, for a symmetry breaking (e.g., transverse), magnetic field such linear stability analysis is not known for the corresponding basic state at such a field configuration. For a detailed description regarding the linearization around the CCF and solution of the linearized NSE, we refer to the Appendix in [43].…”

Section: Linear Stability Behavior and Analysismentioning

confidence: 99%

“…Reindl et al [9] also observed hysteresis between vortex flows with different k when increasing and decreasing the Reynolds numbers Re 1 . The bifurcation thresholds ( Figure 11 ¼ 0 ðÞ is considered in the linearized ferrofluid equations [43]. Right column of Figure 11(2) presents the wavenumber dependence of the corresponding marginal spiral frequencies at the onsets for m ¼ 1SPI.…”

Section: Axial Wavenumber Dependencementioning

confidence: 99%

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Interaction of Magnetic Fields on Ferrofluidic Taylor-Couette Flow

Altmeyer¹

2020

Pattern Formation and Stability in Magnetic Colloids

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When studying ferrofluidic flows, as one example of magnetic flow dynamics, in terms of instability, bifurcation, and properties, one quickly finds out the additional challenges magnetic fluids introduce compared to the investigation of "classical", "ordinary" shear flows without any kind of particles. Approximation of ferrofluids as fluids including point-size particles or, more realistic fine size particles, the relaxation times of the magnetic particle, their interaction between each other, i.e., the agglomeration and chain forming effects, and the interaction/response between any external applied field and the internal magnetization are just few examples of challenges to overcome. Further dependence on the considered model system, the direction of the external applied magnetic field (homogeneous or inhomogeneous) is crucial, as it can break the system symmetry and thus generate new solutions. As a result, the classical Navier-Stokes equations become modified to the more complex ferrohydrodynamical equation of motion, incorporating magnetic field and magnetization of the fluid itself, which typically makes numerical simulations expensive and challenging. This chapter provides an overview of the tasks/difficulties from describing and simulating magnetic particles, their interaction, and thus finally resulting modification in rotating flow structures and in particular instabilities and bifurcation behavior.

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Section: Linear Stability Behavior and Analysismentioning

confidence: 99%

Section: Axial Wavenumber Dependencementioning

confidence: 99%

Interaction of Magnetic Fields on Ferrofluidic Taylor-Couette Flow

Altmeyer¹

2020

Pattern Formation and Stability in Magnetic Colloids

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“…The basic idea consists of supposing that the ferrofluid in which the microbeads are dispersed may undergo a field-induced structuring manifested by the appearance of nanoparticle chains or droplike elongated aggregates extended along the direction of the applied magnetic field [15,31,32]. FIG.…”

Section: A General Frameworkmentioning

confidence: 99%

Kinetics of doublet formation in bicomponent magnetic suspensions: The role of the magnetic permeability anisotropy

et al. 2017

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Micron-sized particles (microbeads) dispersed in a suspension of magnetic nanoparticles, i.e., ferrofluids, can be assembled into different types of structures upon application of an external magnetic field. This paper is devoted to theoretical modeling of a relative motion of a pair of microbeads (either soft ferromagnetic or diamagnetic) in the ferrofluid under the action of applied uniform magnetic field which induces magnetic moments in the microbeads making them attracting to each other. The model is based on a point-dipole approximation for the magnetic interactions between microbeads mediated by the ferrofluid; however, the ferrofluid is considered to possess an anisotropic magnetic permeability thanks to field-induced structuring of its nanoparticles. The model is tested against experimental results and shows generally better agreement with experiments than the model considering isotropic magnetic permeability of ferrofluids. The results could be useful for understanding kinetics of aggregation of microbeads suspended in a ferrofluid. From a broader perspective, the present study is believed to contribute to a general understanding of particle behaviors in anisotropic media.

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“…A theoretical and experimental investigation on the Dean problem of ferrofluids has not gained much attention, though, a significant research work has been done in the parallel problem on the instability of the circular Taylor-Couette ferrofluid flow between concentric rotating cylinders with axial magnetic field [17][18][19][20][21][22][23][24][25][26][27][28]. Some work on mixed convection of ferrofluid in a curved tube has also been reported recently by Aminfar et al [29], where an enhancement of the heat transfer is observed numerically in the presence of externally applied magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Dean instability in ferrofluids

Singh

Bajaj

2015

Meccanica

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The linear instability of the Dean-flow is considered in ferrohydrodynamics (FHD) with respect to the axisymmetric and the non-axisymmetric perturbations. The onset of the instability is influenced by the applied magnetic field, acting along the axis of the cylinders. The applied magnetic field may advance or delay the onset of the instability, depending upon its magnitude and the radius ratio of the cylinders. The preferred mode for the onset of the instability in the Dean problem remains axisymmetric in the presence of the applied magnetic field just as in the absence of the magnetic field. The onset of the instability depends very little on the magnetic nature of the boundaries. The numerical computations indicate that the principle of exchange of stability is valid for the FHD Dean problem.

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Elongational flow effects on the vortex growth out of Couette flow in ferrofluids

Cited by 12 publications

References 31 publications

Interaction of Magnetic Fields on Ferrofluidic Taylor-Couette Flow

Interaction of Magnetic Fields on Ferrofluidic Taylor-Couette Flow

Kinetics of doublet formation in bicomponent magnetic suspensions: The role of the magnetic permeability anisotropy

Dean instability in ferrofluids

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