Magnetic traveling-stripe-forcing: enhanced transport in the advent of the Rosensweig instability

A new kind of contactless pumping mechanism is realized in a layer of ferrofluid via a spatio-temporally modulated magnetic field. The resulting pressure gradient leads to a liquid ramp, which is measured by means of X-rays. The transport mechanism works best if a resonance of the surface waves with the driving is achieved. The behavior can be understood semi-quantitatively by considering the magnetically influenced dispersion relation of the fluid.Comment: 6 Pages, 8 Figure

Influence of Brownian Diffusion on Levitation of Bodies in Magnetic Fluid

The present work deals with experimental investigation of the levitation of magnetic and non-magnetic bodies in a magnetic fluid when essentially influenced by Brownian diffusion of magnetic particles in it. It is established that the point of levitation of bodies in a magnetic fluid varies with time. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3365

The effect of magnetophoresis and Brownian diffusion on the levitation of bodies in a magnetic fluid

New aspects related to the redistribution of magnetic particles concentration in a magnetic fluid caused by magnetophoresis and Brownian diffusion in a nonuniform magnetic field are considered. These aspects deal with the influence of these processes on pressure redistribution and levitation of bodies in a magnetic fluid. It is shown that due to these processes the pressure force acting on bodies changes significantly with time and can be reduced dozens of percent if compared to a homogenous flui

Statics of Magnetic Fluid Drop with Compound Magnetic Core in a Wedge-Shaped Channel

A behavior of magnetic fluid drop with compound magnetic core in a wedge-shaped channel was studied experimentally. The study examines influence of magnetic fluid properties, its volume and magnetic field on statics of the system compound magnet – magnetic fluid drop in wedge-shaped channel. The possibility to change the static conditions of such system by altering magnetic field of the core was observed. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3361

Axisymmetric solitary waves on the surface of a ferrofluid

We report the first observation of axisymmetric solitary waves on the surface of a cylindrical magnetic fluid layer surrounding a current-carrying metallic tube. According to the ratio between the magnetic and capillary forces, both elevation and depression solitary waves are observed with profiles in good agreement with theoretical predictions based on the magnetic analogue of the Korteweg-deVries equation. We also report the first measurements of the velocity and the dispersion relation of axisymmetric linear waves propagating on the cylindrical ferrofluid layer that are found in good agreement with theoretical predictions.Comment: to be published in Phys. Rev. Let

The Shape of the Magnetic Fluid Surface above a Magnetizable Sphere in a Uniform Magnetic Field

The shape of the free surface of a magnetic fluid above a spherical ferromagnetic body immersed in it in a uniform magnetic field is investigated experimentally. The effect of the direction and magnitude of the magnetic field on the deformation characteristics of the free surface of the magnetic fluid with various magnetic properties and geometrical parameters is established

Features of the Behavior of a Plane Axisymmetric Magnetic Fluid Drop in a Nonmagnetic Solvent and a Uniform Magnetic Field

The work is devoted to an experimental study of the process of dissolution of a magnetic fluid in a nonmagnetic solvent under the action of a uniform magnetic field. It is experimentally established that in a volume of magnetic fluid surrounded by a miscible solvent fluid, under the action of a uniform magnetic field, a mechanical movement arises, triggering deformation of this volume. Initially, the axisymmetric volume of the fluid takes an ellipsoidal shape, lengthening along the magnetic field direction. The main reason for this movement is the pressure differences in the magnetic fluid, caused by jumps and nonuniformities of the magnetic field at the interface between magnetic and nonmagnetic media. Simultaneously with the mechanical motion, the diffusion dissolution of the magnetic fluid occurs, which is also accompanied by the motion of the diffusion front at the interface between the fluids. The concentration gradients of magnetic particles that arise in this case cause gradients of the magnetization of the fluid and, as a consequence, gradients of the magnetic field intensity. Together, this triggers the appearance of a bulk magnetic force in the magnetic fluid, and the pressure gradients associated with it. The main regularities of this process have been established, viz. the dependence of change of the geometric characteristics of the volume and its deformation rate on time. It is shown that at the initial stage of the process, the rates of mechanical movement of the boundaries of the magnetic fluid volume are much higher than the rates of movement of the diffusion front. Thus, the initial rate of mechanical elongation of the droplet under the experimental conditions is 0.25 mm/min, and the diffusion front rate is 0.08 mm/min. Over time, these processes slow down and stop when the volume of the magnetic fluid is completely dissolved. Herewith, the mechanical elongation of the drop is the first to stop and, in the case under consideration, takes about ten minutes

Особенности поведения плоской осесимметричной капли магнитной жидкости в немагнитном растворителе в однородном магнитном поле

The work is devoted to an experimental study of the process of dissolution of a magnetic fluid in a nonmagnetic solvent under the action of a uniform magnetic field. It is experimentally established that in a volume of magnetic fluid surrounded by a miscible solvent fluid, under the action of a uniform magnetic field, a mechanical movement arises, triggering deformation of this volume. Initially, the axisymmetric volume of the fluid takes an ellipsoidal shape, lengthening along the magnetic field direction. The main reason for this movement is the pressure differences in the magnetic fluid, caused by jumps and nonuniformities of the magnetic field at the interface between magnetic and nonmagnetic media. Simultaneously with the mechanical motion, the diffusion dissolution of the magnetic fluid occurs, which is also accompanied by the motion of the diffusion front at the interface between the fluids. The concentration gradients of magnetic particles that arise in this case cause gradients of the magnetization of the fluid and, as a consequence, gradients of the magnetic field intensity. Together, this triggers the appearance of a bulk magnetic force in the magnetic fluid, and the pressure gradients associated with it. The main regularities of this process have been established, viz. the dependence of change of the geometric characteristics of the volume and its deformation rate on time. It is shown that at the initial stage of the process, the rates of mechanical movement of the boundaries of the magnetic fluid volume are much higher than the rates of movement of the diffusion front. Thus, the initial rate of mechanical elongation of the droplet under the experimental conditions is 0.25 mm/min, and the diffusion front rate is 0.08 mm/min. Over time, these processes slow down and stop when the volume of the magnetic fluid is completely dissolved. Herewith, the mechanical elongation of the drop is the first to stop and, in the case under consideration, takes about ten minutes.Работа посвящена экспериментальному исследованию процесса растворения магнитной жидкости в немагнитном растворителе под действием однородного магнитного поля. Экспериментально установлено, что в объеме магнитной жидкости, окруженном смешивающейся с ней жидкостью-растворителем, под действием однородного магнитного поля возникает механическое движение, приводящее к деформации этого объема. Первоначально осесимметричный объем жидкости принимает эллипсоидальную форму и удлиняется вдоль направления магнитного поля. Основной причиной этого движения являются перепады давления в магнитной жидкости, вызванные скачками и неравномерностями магнитного поля на границе раздела магнитных и немагнитных сред. Одновременно с механическим движением происходит диффузионное растворение магнитной жидкости, которое также сопровождается движением диффузионного фронта на границе раздела жидкостей. Возникающие при этом градиенты концентрации магнитных частиц вызывают градиенты намагниченности жидкости и, как следствие, градиенты напряженности магнитного поля. В совокупности это приводит к возникновению объемной магнитной силы в магнитной жидкости и связанных с ней градиентах давления. Установлены основные закономерности этого процесса: зависимость изменения геометрических характеристик объема и скорости его деформации от времени. Показано, что на начальном этапе процесса скорость механического движения границ объема магнитной жидкости значительно превышает скорость движения диффузионного фронта. Так, начальная скорость механического удлинения капли в условиях эксперимента составляет 0,25 мм/мин, а скорость распространения диффузионного фронта 0,08 мм/мин. Со временем эти процессы замедляются и прекращаются, когда объем магнитной жидкости полностью растворяется. При этом механическое удлинение капли прекращается первым и в рассматриваемом случае занимает порядка десятка минут

Effect of magnetophoresis and Brownian diffusion on mechanical processes in magnetic fluids: The role of a condensation phase transition

In this work, we study theoretically the effect of the mass transfer processes on the volume magnetic force and viscous friction of the magnetic fluid subjected to a magnetic field gradient and a shear flow between two rotating cylinders. The model is based on the diffusion equations and takes into account a condensation phase transition in the magnetic fluid. The results of experimental and theoretical studies of the diffusion processes in a thin layer of the magnetic fluid are also presented. © 2019 Elsevier B.V.One of the authors (PK) acknowledges financial support from the French ANR Project Future Investments UCA JEDI, No. ANR-15-IDEX-01 (projects ImmunoMag and MagFilter). AZ is grateful to the program of the Ministry of Education and Science of the Russian Federation, projects 02.A03.21.0006; 3.1438.2017/4.6

On the mechanics of magnetic fluids with field-induced phase transition: Application to Couette flow

The influence of Brownian diffusion and magnetophoresis, which are followed by phase transition, on the characteristics of a stationary plane Couette flow of magnetic fluid in a non-uniform magnetic field is discussed. The phase transition conditions in magnetic fluids are assumed as a natural restriction to the particle concentration increase in a non-uniform magnetic field. Profiles of the particles' concentration are calculated, and dependences of the volume magnetic force and of the viscous force are established. © 2018 Institute of Physics, University of Latvia