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

Solitary waves on a ferrofluid jet

The propagation of axisymmetric solitary waves on the surface of an otherwise cylindrical ferrofluid jet subjected to a magnetic field is investigated. An azimuthal magnetic field is generated by an electric current flowing along a stationary metal rod which is mounted along the axis of the moving jet. A numerical method is used to compute fully-nonlinear travelling solitary waves and predictions of elevation waves and depression waves by Rannacher & Engel (2006) using a weakly-nonlinear theory are confirmed in the appropriate ranges of the magnetic Bond number. New nonlinear branches of solitary wave solutions are identified. As the Bond number is varied, the solitary wave profiles may approach a limiting configuration with a trapped toroidal-shaped bubble, or they may approach a static wave (i.e. one with zero phase speed). For a sufficiently large axial rod, the limiting profile may exhibit a cusp

Non-Monotonic Dispersion of Surface Waves in Magnetic Fluids

The dispersion relation of surface waves of a magnetic fluid in a magnetic field is studied experimentally. We verify the theoretically predicted existence of a non-monotonic dispersion relation. In particular, we demonstrate the existence of two different wave numbers occuring at the same frequency in an annular geometry.Comment: RevTex-file, 4 sty-files, 9 ps-files, 3 GIF'

Behavior of nanoparticle clouds around a magnetized microsphere under magnetic and flow fields

When a micron-sized magnetizable particle is introduced into a suspension of nanosized magnetic particles, the nanoparticles accumulate around the microparticle and form thick anisotropic clouds extended in the direction of the applied magnetic field. This phenomenon promotes colloidal stabilization of bimodal magnetic suspensions and allows efficient magnetic separation of nanoparticles used in bioanalysis and water purification. In the present work, size and shape of nanoparticle clouds under the simultaneous action of an external uniform magnetic field and the flow have been studied in details. In experiments, dilute suspension of iron oxide nanoclusters (of a mean diameter of 60 nm) was pushed through a thin slit channel with the nickel microspheres (of a mean diameter of 50$\mu$m) attached to the channel wall. The behavior of nanocluster clouds was observed in the steady state using an optical microscope. In the presence of strong enough flow, the size of the clouds monotonically decreases with increasing flow speed in both longitudinal and transverse magnetic fields. This is qualitatively explained by enhancement of hydrodynamic forces washing the nanoclusters away from the clouds. In the longitudinal field, the flow induces asymmetry of the front and the back clouds. To explain the flow and the field effects on the clouds, we have developed a simple model based on the balance of the stresses and particle fluxes on the cloud surface. This model, applied to the case of the magnetic field parallel to the flow, captures reasonably well the flow effect on the size and shape of the cloud and reveals that the only dimensionless parameter governing the cloud size is the ratio of hydrodynamic-to-magnetic forces - the Mason number. At strong magnetic interactions considered in the present work (dipolar coupling parameter $\alpha \geq 2$), the Brownian motion seems not to affect the cloud behavior

Dynamics of a Single Peak of the Rosensweig Instability in a Magnetic Fluid

To describe the dynamics of a single peak of the Rosensweig instability a model is proposed which approximates the peak by a half-ellipsoid atop a layer of magnetic fluid. The resulting nonlinear equation for the height of the peak leads to the correct subcritical character of the bifurcation for static induction. For a time-dependent induction the effects of inertia and damping are incorporated. The results of the model show qualitative agreement with the experimental findings, as in the appearance of period doubling, trebling, and higher multiples of the driving period. Furthermore a quantitative agreement is also found for the parameter ranges of frequency and induction in which these phenomena occur.Comment: 21 pages, 9 figures, using elsart, submitted to Physica D; revised version with 2 figures and references adde

Stochastic Dynamics of the Specialized Vehicle with Nonlinear Suspension

This work deals with the theoretical modelling of the vertical dynamics of the vehicle which has an additional level of suspension for a cargo platform with the nonlinear stiffness. The paper presents the design scheme of the additional level of cushioning having a quasi-zero stiffness in the equilibrium position. The mathematical model of the dynamic behavior of specialized vehicles is developed as a nonlinear discrete system. The results of numeric calculations of the vehicle dynamic response on the stochastic load is represented based on the developed model. Vertical vibrations of the cargo platform caused by the kinematics random influence applied to the axels of the vehicle are analyzed. The load is applied to the axels of the vehicle with a time delay. The results of the comparative analysis are displayed for the frequencies and amplitudes of the vehicle vertical vibrations within two different suspensions: in the linear and nonlinear statements

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

Influence of Mass Transfer Processes on Couette Flow of Magnetic Fluid

This article describes the results of a theoretical study of magnetic fluid two-dimensional Couett flow in magnetic fluid seal model in view of mass transfer processes. It has been shown that very inhomogeneous magnetic field in seal gap lead to magnetic particle concentration rearrangement due to magnetophoresis and Brownian diffusion. In turn, it lead to inhomogeneous magnetic fluid viscosity and change in local and integral shearing force at channel walls. Integral shearing force has been shown to depend on magnetic field and magnetic fluid parameters. Closely-packed fluid density distribution conditions have been defined. Proposed theory covers real magnetic fluid seal performance features adequately. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3360

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