Magnetic Fluid Column Research Articles

A novel pattern in nonlinear interfacial stability for a magnetic fluid column subject to an axial rotation

Nonlinear differential equations that control the propagation of a surface wave through the surface disconnection between two fluids are described by the Helmholtz–Duffing oscillator having imaginary damping forces. This oscillator is solved without using any perturbation techniques. This study is relevant in many fields such as nanotechnology. Along with the nonlinear analysis, the periodic solution and the stability criteria are established. Numerical calculations for stability conditions showed vital changes in the stability behavior due to the presence of the rotation ratio.

Динамика магнитных жидкостей, подвергающихся колебательному сдвигу

The purpose of the work: to study the dynamics of the volume of a magnetic fluid levitating in an external magnetic field experiencing an oscillatory shift. Metods. The experiments were carried out on installations developed on the basis of known methods and equipment for magnetic measurements and manufactured independently. We study samples of magnetic fluid based on magnetite Fe3O4 stabilized with oleic acid. Kerosene was used as a carrier fluid. Results. Samples of a magnetic fluid with different physical parameters are considered, and the dependence of the viscosity on the magnetization of the magnetic field is investigated. The increase in viscosity in a magnetic field upon the action of a levitating MF column on the interface can be explained by an increase in particle interactions, which lead to MF microstructuring in the near-wall layer. The microstructure of the sample and the presence of large magnetic particles exert the greatest influence on the dynamics of a magnetic fluid, which undergoes an oscillatory shift and magnetoviscous effect. Conclusion. An assessment of the viscous magnetism effect in a thin near-wall layer of a column of magnetic fluid vibrating in a tube is made when a strong magnetic field is applied. The calculation of the viscosity value is carried out according to the formula obtained on the basis of two different theoretical approaches. The results of the work can be used to develop a method for express testing of magnetic fluid samples, as well as to develop acceleration and vibration sensors based on magnetic fluids. This method can be used to study magnetophoresis and aggregation of nanoparticles. Information on the viscous magnetic effect will be valuable for microfluidic technologies, where magnetic fluids with anisotropic particles, functionalized with various specific surfactants and flowing in microchannels, are used.

An alternative way to study magnetic fluid magnetization and viscosity

In the article, magnetization, viscosity and its increment (“magnetoviscous” effect) in a thin near-wall layer of the column of magnetic fluid that oscillates in the tube when applying a strong transverse magnetic field are assessed. Calculations were performed using formulae obtained on the basis of two different theoretical approaches. The described technique is of interest for studying magnetophoresis and the processes of aggregation of magnetic nanoparticles.

The behaviour of gas inclusions in a magnetic fluid in a non-uniform magnetic field

The findings of the experimental research of a phased air cavity capture in a flat channel with a magnetic fluid located along the axis of the annular magnet influenced by the changing in sign magnetic field are discussed. The research was carried out with four magnetic fluids with the magnetic phase concentrations of 1.93%; 2.70%; 4.34%; 9.08%. The analysis of the obtained results is presented within the framework of the electrodynamic model of “low magnetic bodies” based on the development of the system of isolines of the module of the magnetic field intensity. The provided data, first, clarify the conclusions of the previous interpretation of the air cavity capture with an opaque magnetic fluid column, and second, can be useful to solve practical issues of microhydraulics.

“Wall Viscosity” of Magnetic Fluid Oscillations in a Strong Magnetic Field

The authors provide an estimation of the “wall viscosity” and its increment (“magneto-viscous” effect) in a thin near-wall layer of a column of magnetic fluid oscillating in the tube when a strong transverse magnetic field is applied. The calculation is performed according to the formula obtained on the basis of two different theoretical approaches and applied to the previously published experimental results of the complex measurement of oscillation frequency and saturation magnetization of the magnetic fluid. These results are commented upon, stemming from the assumed absence of the field dependence of viscosity. The estimates of “wall viscosity” “from above” and “from below” are used to calculate their contribution to the damping coefficient of oscillations.

Viscosity of Magnetic Fluid in Oscillation System in a Strong Magnetic Field

The article gives an assessment of viscosity and its increment (‘magnetoviscous’ effect) in a thin near-wall layer of the column of magnetic fluid that oscillates in the tube when applying a strong transverse magnetic field. Viscosity is calculated according to a formula derived from two different theoretical approaches. For calculation, previously published experimental results, which were discussed earlier on the assumption that there is no field dependence of viscosity, are used in the article. A comparative analysis of the “near-wall viscosity” estimates obtained using dynamic elasticity as well as the magnetization curve and the coefficient of static elasticity is carried out. The significance of the results obtained for ‘magnetoviscous’ effect for performing diagnosis of interparticle aggregation is indicated.

Optical fiber F–P magnetic field sensor based on magnetostrictive effect of magnetic fluid

Abstract magnetic field sensor of air-gap Fabry–Perot fiber interferometersis proposed based on magnetostrictive effect. The sensor is consisted of single-model fiber (SMF), air-gap, no-core fiber (NCF) and magnetic fluid. Those are sealed in the capillary, SMF and NCF are connect with air chamber and magnetic fluid column. With the presence of an external magnetic field, air chamber cavity length changes because of the magneto-volume variation of magnetic fluids. This situation causes a change in the optical path difference. Detection of the drift of interference spectrum leads to the detection of the change in magnetic field. When the magnetic field is parallel to the direction in which the capillary is placed, the sensitivity is 0.2347 nm/mT; when the magnetic fluid is perpendicular to the direction in which the capillary is placed, the sensitivity is 0.325 nm/ mT. In addition to this new magnetic fluid sensor, a practical detection system is built, which relative error rate is less than 2%.

Mechanics of magnetic fluid active element in strong magnetic field

Measurements and theoretical analysis of the processes of static displacement and oscillations of the magnetic fluid column confined by magnetic levitation in a strong magnetic field in a horizontally placed tube are carried out. The calculations of the saturation magnetization, made on the basis of the obtained results of the displacement and the oscillation frequency for the sample of the magnetic fluid under study, are in good agreement with the experimental data. The described technique is of interest when studying saturation magnetization, magnetophoresis, aggregation of nanoparticles and their temporal dependence in magnetic colloids.

Shear and oscillations of the magnetic fluid column in a strong magnetic field

Shear and oscillations of the magnetic fluid column in a strong magnetic field

Dynamic Elasticity of a Magnetic Fluid Column in a Strong Magnetic Field

The elastomagnetic parameters of a magnetic fluid kept by magnetic levitation in a tube placed horizontally in a strong magnetic field are measured, including the oscillation frequency, the ponderomotive and dynamic elasticity coefficients, the magnetization curve, and the magnetic field strength and its gradient. Results of calculations for the model of ponderomotive elasticity for the examined sample of the magnetic fluid corrected for the resistance of the moving viscous fluid are in good agreement with the experimental magnetization curve. The described method is of interest for a study of magnetophoresis, nanoparticle aggregations, viscosity, and their time dependences in magnetic colloids.

Oscillations of Magnetic Fluid Column in Strong Magnetic Field

The paper considers the results of measuring the elastic parameters (ponderomotive elasticity coefficient, oscillation frequency, attenuation coefficient) of the oscillatory system with an inertial element that is a magnetic fluid column retained in a tube due to magnetic levitation in a strong magnetic field. Elasticity is provided by the ponderomotive force which affects the upper and lower thin layers of the fluid column. Measurement results of vibration parameters of the oscillatory system can be useful for the investigations of magnetophoresis and aggregation of nanoparticles in magnetic fluids.

Mechanics of magnetic fluid column in strong magnetic fields

Elastic-and magnetic properties of magnetic fluid confined by ponderomotive force in a tube fixed in horizontal position are considered. The system is placed in a strong magnetic field under the influence of external static and dynamic perturbations. An experimental setup has been developed. A theoretical basis of the processes of magnetic colloid elastic deformation has been proposed. The values of the static ponderomotive elasticity coefficient and the elasticity coefficient under dynamic action are experimentally determined. The calculations of the saturation magnetization for two magnetic fluid samples, carried out according to the equation containing the dynamic elasticity coefficient, are in good agreement with the experimental magnetization curve. The described method is of interest when studying magnetophoresis and aggregation of nanoparticles in magnetic colloids.

Vibrating Properties of a Magnetic-Fluid Tuned Liquid Column Damper with Different U-Pipes

A magnetic-fluid tuned liquid column damper (MF-TLCD) is a semi-active damper that has a magnetic fluid column in U-pipe as an additional vibration system. An MF-TLCD can suppress structural vibrations at a wide frequency range by applying a magnetic field. In this study, we performed vibration experiments for three types of U-pipes and assessed the effects on MF-TLCD performance caused by different damping forces on the liquid column.

Free oscillations of magnetic fluid in strong magnetic field

The paper presents the esults of measuring the elastic parameters of an oscillatory system (coefficient of pondermotive elasticity, damping factor, and oscillation frequency) whose viscous inertial element is represented by a magnetic fluid confined in a tube by magnetic levitation in a strong magnetic field. The role of elasticity is played by the pondermotive force acting on thin layers at the upper and lower ends of the fluid column. It is shown that, by measuring the elastic oscillation frequencies of the magnetic fluid column, it is possible to develop a fundamentally new absolute method for determining the saturation magnetization of a magnetic colloid.

磁性流体を用いた同調液柱管ダンパーにおける液柱減衰力の変化が制振力に及ぼす影響

Magnetic fluid tuned liquid column damper (MF-TLCD) is a kind of semi-active damper that uses magnetic fluid as its working fluid. An MF-TLCD alters the natural frequency of the magnetic fluid column that forms the resident liquid inside the MF-TLCD by applying a magnetic field. We quantitatively investigated the damping coefficient generated by the flow of magnetic fluid, which is strongly related to the damping performance. Three kind of U-pipes that have each different shape ((1) conventional (2) equipped with an orifice (3) curved fluently) were prepared and single-degree-of-freedom oscillation was performed with each those pipes. Finally, we discussed the effect to the damping performance of MF-TLCD induced by various damping coefficient subjected to magnetic field and configurations of those U-pipes.

Instability and disintegration of a magnetic fluid column that surrounds a long porous core

A mathematical model of the propagation and instability of waves on the surface of an infinite-length cylindrical magnetic Liquid column that surrounds a coaxially situated long porous core of circular cross-section is formulated and investigated. Conditions are found for the perturbations of the liquid column surface to become unstable and to lead to its disintegration into a chain of connected drops. It is shown that the length of these drops increases with magnetic field.

Frequency Analysis of Semi-Active Tuned Magnetic Fluid Column Damper with Two Electromagnets

A new semi-active tuned liquid column damper (TLCD) that uses magnetic fluid as its working fluid (MF-TLCD) is presented. An MF-TLCD alters the natural frequency of the magnetic fluid column that forms the resident liquid inside the MF-TLCD by applying a magnetic field. We investigated the damping characteristics of an MF-TLCD equipped with two electromagnets, and also the transition of the natural frequency, which is strongly related to the damping performance. The coupled structure-MF-TLCD system was investigated both experimentally and by numerical analysis. The momentum equation of an MF-TLCD and its numerical solution are presented. The numerical results are validated by comparison with experimental results.

Oscillations of a bubble separated from an air cavity under compression caused by magnetic field in a magnetic fluid

Based on the concept of mapping the free surface geometry of a weakly magnetic medium by the topography of isolines of the magnetic field strength magnitude, the shape of the free surface of a magnetic fluid is studied in the static state at two stages: the initial stage, where an annular magnet is moving toward the surface of the magnetic fluid column in a tube, and at the stage where the air cavity is pressed to the bottom. It is shown that the separation of bubbles from the air cavity occurs at the magnet axis in the immediate vicinity of the magnet symmetry plane. A method and an experimental setup are proposed to investigate possible electromagnetic indication of the size of air bubbles formed in the magnetic fluid. The results of an experimental study of bubble separation from an air cavity held in the magnetic fluid and compressed by the pondermotive forces of the magnetic field are discussed. The results may be of importance for designing a new technique for metering small gas shots to a reactor.

0802 磁性流体を用いた同調液柱管ダンパーの線形化手法による周波数応答解析(OS8-1 機能性流体工学の融合化新展開,OS8 機能性流体工学の融合化新展開)

In this paper, frequency response analysis of a tuned liquid column damper using magnetic fluid (MF-TLCD) based on a linearized method was presented. An MF-TLCD alters the natural frequency of the magnetic fluid column that forms the resident liquid inside the MF-TLCD by applying a magnetic field. The interaction equations of motion under a harmonic type of loading for SDOF damped structure and liquid surface motion in a MFTLCD were expressed. The damping term induced by liquid flows and the magnetic force term were linearized to derive analytical solutions. The analytical results were compared with experimental results.

Nonlinear shape oscillations of axisymmetric magnetic fluid columns in a magnetic field

Nonlinear axisymmetric shape oscillations have been revealed through experiments conducted with large-amplitude forced vertical vibrations of a magnetic fluid column supported by a magnetic field in the presence of gravity. Those nonlinear shape oscillations are characterized by the jumping phenomena, mode transition, and subharmonic motions.