Measurement of the torque on diluted ferrofluid samples in rotating magnetic fields

Storozhenko, A; Stannarius, Ralf; Tantsyura, A. O.; Shabanova, I. A.

doi:10.1016/j.jmmm.2016.09.036

Cited by 8 publications

(3 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In literature occasionally referred to as negative viscosity of the ferrofluid 20,31 . Other works also focussed on the dependence of particle agglomeration under rotating field 32 .…”

Section: Sebastian Altmeyermentioning

confidence: 99%

On the ridge of instability in ferrofluidic Couette flow via alternating magnetic field

Altmeyer

2021

Sci Rep

View full text Add to dashboard Cite

There is a huge number of natural and industrial flows, which are subjected to time-dependent boundary conditions. The flow of a magnetic fluid under the influence of temporal modulations is such an example. Here, we perform numerical simulations of ferrofluidic Couette flow subject to time-periodic modulation (with frequency $$\Omega _H$$ Ω H ) in a spatially homogeneous magnetic field and report how such a modulation can lead to a significant Reynolds number Re enhancement. Consider a modified Niklas approximation we explain the relation between modulation amplitude, driving frequency and stabilization effect. From this, we describe the system response around the primary instability to be sensitive/critical by an alternating field. We detected that such an alternating field provides an easy and in particular accurate controllable key parameter to trigger the system to change from subcritical to supercritical and vice versa. Our findings provide a framework to study other types of magnetic flows driven by time-dependent forcing.

show abstract

“…In literature occasionally referred to as negative viscosity of the ferrofluid 20,31 . Other works also focussed on the dependence of particle agglomeration under rotating field 32 .…”

Section: Sebastian Altmeyermentioning

confidence: 99%

On the ridge of instability in ferrofluidic Couette flow via alternating magnetic field

Altmeyer

2021

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Among the works describing the RMF, are also those that concern the low-frequency range f < 1 kHz, where generation is performed by mechanical rotation of permanent magnets [23][24][25]. These solutions are not applicable in hyperthermia therapy.…”

Section: Introductionmentioning

confidence: 99%

Two-Phase System for Generating a Higher-Frequency Rotating Magnetic Field Excited Causing Hyperthermic Effect in Magnetic Fluids

Skumiel

Wojciechowski

2022

Energies

View full text Add to dashboard Cite

This article presents a new method of excitation for a fast-changing rotating magnetic field (RMF) of higher frequencies (HF) causing the hyperthermic effect in magnetic fluids. The method proposed here uses a magnetic field exciter (inductor) consisting of a ferrite magnetic circuit and a system of coils connected in a two-phase arrangement. The proposed system is powered by two higher-frequency rectangular signals, with a 90-degree phase shift between each other, through HF transformers with ferrite cores. This paper presents the outcomes of the operation of RMFs in the frequency range of 38 kHz to 190 kHz, with a value of amplitude of magnetic field intensity H equal to 20 kA/m and increasing temperature, in a sample of APG513 magnetic liquid. The obtained results show that, in the range of the magnetic field intensities of moderate values, at a constant frequency f, the values of the time derivative of temperature are proportional to the square of the magnetic field intensity dT/dt ~ H2. Moreover, the values of the temperature rate, which are measured with the constant value of the magnetic field intensity, are proportional to the square of the frequency dT/dt ~ f 2. At higher amplitudes of the RMF, the relationship dT/dt ~ H2 is no longer fulfilled, and an inflexion point of this function appears. In the case of the highest values of the achieved intensity amplitudes (H = 20 kA/m), the parameter of the Langevin function achieves a value equal to ξ = 6.

show abstract

“…These focused on various aspects, as different field orientations, agglomeration, internal magnetization, torque measurements, etc. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. The common conclusion of all these works is the fact that a static magnetic field, independently of its orientation stabilizes the basic state (Circular Couette flow, CCF), i.e., moving the bifurcation threshold of the primary instability to greater values of the respective control parameter (e.g., the inner Reynolds number Re i ).…”

mentioning

confidence: 99%

Increasing Flow Complexity in Time-Dependent Modulated Ferrofluidic Couette Flow

Altmeyer¹

2022

Fluid Dyn

View full text Add to dashboard Cite

⎯We present numerical simulations of ferrofluidic Couette flow in between counter-rotating cylinders with a spatially homogeneous magnetic field but subject to time-periodic modulation. Such a modulation can lead to a significant inner Reynolds number () enhancement for primary bifurcating solutions, for either helical or toroidal flow structures. Moreover, the external introduced modulation frequency renders the different solutions to step up one level in the hierarchy of complexity. Fixed point solutions become limit cycles and limit cycles become 2-tori. Moreover, for sufficiently strong modulation amplitudes of the magnetic field stability can be exchanged between primary bifurcating spiral and ribbon solutions, both appearing at a common threshold. In addition, a stable bifurcation branch with direct connection of ribbon and Taylor vortices via wavy Taylor vortices is found.

show abstract

Measurement of the torque on diluted ferrofluid samples in rotating magnetic fields

Cited by 8 publications

References 36 publications

On the ridge of instability in ferrofluidic Couette flow via alternating magnetic field

On the ridge of instability in ferrofluidic Couette flow via alternating magnetic field

Two-Phase System for Generating a Higher-Frequency Rotating Magnetic Field Excited Causing Hyperthermic Effect in Magnetic Fluids

Increasing Flow Complexity in Time-Dependent Modulated Ferrofluidic Couette Flow

Contact Info

Product

Resources

About