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

Mathematical modeling of the vibration characteristics of a specialized vehicle with a double-leveled system of nonlinear suspension moving thru the unit road irregularity

Стаття присвячена вивченню ефективності застосування нелінійного дворівневого підресорювання спеціальних транспортних засобів, яке спрямоване на підвищення плавності їх ходу. Наведені результати теоретичних досліджень, щодо характеристик відповідного транспортного засобу, як нелінійної системи. Побудовано математичну нелінійну дискретну динамічну модель даного транспортного засобу, на основі якої проведено серію досліджень щодо вільних коливань транспортного засобу. Наведено результати порівняльного аналізу щодо частот та амплітуд коливань які встановлюються в транспортному засобі в лінійній та запропонованій дворівневій нелінійній компоновках при імпульсному збудженні, що прикладається до коліс даного транспортного засобу.Статья посвящена изучению эффективности применения нелинейного двухуровневого подрессоривания специальных транспортных средств, которое направлено на повышение плавности их хода. Приведенные результаты теоретических исследований, в характеристиках соответствующего транспортного средства, как нелинейной системы. Построена математическая нелинейную дискретную динамическую модель данного транспортного средства, на основе которой проведена серия исследований относительно свободных колебаний транспортного средства. Приведены результаты сравнительного анализа по частотам и амплитудам колебаний которые устанавливаются в транспортном средстве в линейной и предложенной двухуровневой нелинейной компоновках при импульсном возбуждении, которое прикладывается к колесам данного транспортного средства.The work deals with the definition of an effective way of the suspension on the specialized vehicles and is aimed on improvement of the smoothness of its movement (riding comfort). A riding comfort is an important operational feature of the modern vehicles that allow to protect the passengers and goods from the influence of the vibrations during the vehicle movement. These are especially important for the transportation of the dangerous goods. The paper presents the design scheme of specialized vehicles, which has additional level of cushioning, with the nonlinear characteristic, which has a quasi-zero stiffness in the equilibrium position. The mathematical model of the dynamic behavior of the specialized vehicles are developed as a nonlinear discrete system. The results of numeric calculations of the dynamic response of the vehicle on the impact is presented based on the developed model. A vertical vibrations of the luggage platform is analyzed caused by the kinematics impact that applied on the axis of the vehicle. The load is applied on the axis of the vehicle with time delay providing its vertical vibrations. The results of the comparative analysis is shown for the frequencies and amplitudes of the vehicle vertical vibrations within two different suspensions: in the linear and nonlinear statements under impact excitation

Surface instabilities of ferrofluids

We report on recent progress in understanding the formation of surface protuberances on a planar layer of ferrofluid in a magnetic field oriented normally to the surface. This normal field or Rosensweig instability can be tackled by a linear and a nonlinear description. In the linear regime of small amplitudes we focus on the wave number of maximal growth, its corresponding growth rate and the oscillatory decay of metastable pattern, accessible via a pulse technique. A quantitative comparison of measurements with predictions of the linear stability analysis is performed, whereby the viscosity and the finite depth of the liquid layer are taken into account. In the nonlinear regime the fully developed peak pattern can be predicted by a minimization of the free energy and by numerics employing the finite element method. For a comparison with the results of both methods, the three-dimensional surface profile is recorded by a radioscopic measurement technique. In the bistable regime of the flat and patterned state we generate localized states (ferrosolitons) which are recovered in analytical and numerical model descriptions. For higher fields an inverse hysteretic transition from hexagonal to square planforms is measured. % Via a horizontal field component the symmetry can be broken in the experiment, resulting in liquid ridges and distorted hexagons, as predicted by theory. Replacing ferrofluid by ferrogel also an elastic energy contribution has to be taken into account for a proper model description, yielding a linear shift of the threshold and an increased bistability range. Parametric excitation in combination with magnetic fields is widening the horizon of pattern formation even further. For the mono-spike oscillator harmonic and subharmonic response as well as deterministic chaos is observed and modeled. In a ring of spikes the formation of domains of different wavelengths and spatio-temporal intermittency is quantitatively studied. For an extended layer of ferrofluid we predict that a stabilizing horizontal field counteracted by vertical vibrations will result in oblique rolls with preselected orientation