Fluid In Magnetic Field Research Articles

Viscous Flow of Two-Component Electron Fluid in Magnetic Field

Viscous Flow of Two-Component Electron Fluid in Magnetic Field

Combined impact of Lorentz force, micro-rotation, and thermo-migration of particles: Dynamics of micropolar fluids experiencing nonlinear thermal radiation and activation energy

The functional qualities of magneto-micropolar fluid with tiny particles allow for increased lubricating oil usage, increased industrial output, and the development of nanotechnology. However, in such a situation, little or nothing is known about the significance of Lorentz force associated with the behaviour of conducting fluids in magnetic fields, micro-rotation, and thermo-migration of particles as applicable to the control of liquid metals or plasmas. This study focuses on the combined impact of Lorentz force, micro-rotation, and thermo-migration of particles on the dynamics of micropolar fluids experiencing nonlinear thermal radiation and Arrhenius chemical reaction associated with the activation energy. The reactive non-Newtonian, magneto-micropolar nanoparticle fluid flows over a configured two-dimensional stretchy vertical plate. The flow is influenced by activation energy, Brownian movement of tiny particles, thermo-migration of particles and nonlinear thermal radiation. By means of suitable similarity quantities, the partial differential equations governing the flow equations are reduced to ordinary differential equations, and solved numerically using Fehlberg integrating Runge–Kutta scheme. It is worth concluding that the Lorentz force, micro-rotation, and thermo-migration of particles strongly affects the dynamics of micropolar fluids near the wall. A tiny number of particle spins produced by collisions with the boundary dominate the micro-rotation field.

Viscous flow of two-component electron fluid in magnetic field

In pure conductors with a low density of defects, frequent electron-electron collisions can lead to the formation of a viscous fluid consisting of conduction electrons. In this work, is studied magnetotransport in a viscous fluid consisting of two types of electrons, for which some of their parameters are different. The difference between such system and the one-component electron fluid is as follows. The scattering of electrons with their transitions from one component to another can lead to an imbalance in flows and concentrations, which affects the flow as a whole. In this work, the balance transport equations for such a system are constructed and solved for the case of a long sample with rough edges. The equation for the flow of the unbalance value towards the edges contains the bulk viscosity term. It is shown that in sufficiently wide samples, the transformation of particles into each other during scattering leads to the formation of a single viscous fluid flowing as a whole, while in narrow samples the two components flow as two independent fluids. The width of the sample at which this transition occurs is determined by the internal parameters of the fluid and the magnitude of magnetic field. The distributions of the flow of the fluid components over a sample cross section and the magnetoresistance of a sample are calculated. The latter turns out to be positive and saturating, corresponding to the transition with increasing of magnetic field from independent Poiseuille flows of the two components to the Poiseuille flow of a uniform fluid. Keywords: electron fluid, viscosity, two-component system, nanostructures, magnetoresistance.

Numerical study of the unsteady 2D coupled magneto-hydrodynamic equations on regular/irregular pipe using direct meshless local Petrov–Galerkin method

The study of the conduction of fluids in magnetic fields has attracted a lot of interest in recent years. In this paper, we use new truly meshless methods for numerical solving of the unsteady 2D coupled magneto-hydrodynamic (MHD) equations with uniform and scattered distributions of nodes on regular and polar domains. These methods are implemented based on a generalization of the moving least squares approximation (GMLS) method and local weak forms of MHD equations. By observing the numerical results obtained from these methods and comparing them with others, one can find the efficiency, accuracy, and speed of these methods.

Effect of Magnetic Nanofluids on the Performance of a Fin-Tube Heat Exchanger

As electrical devices become smaller, it is essential to maintain operating temperature for safety and durability. Therefore, there are efforts to improve heat transfer performance under various conditions, such as using extended surfaces and nanofluids. Among them, cooling methods using ferrofluid are drawing the attention of many researchers. This fluid can control the movement of the fluid in magnetic fields. In this study, the heat transfer performance of a fin-tube heat exchanger, using ferrofluid as a coolant, was analyzed when external magnetic fields were applied. Permanent magnets were placed outside the heat exchanger. When the magnetic fields were applied, a change in the thermal boundary layer was observed. It also formed vortexes, which affected the formation of flow patterns. The vortex causes energy exchanges in the flow field, activating thermal diffusion and improving heat transfer. A numerical analysis was used to observe the cooling performance of heat exchangers, as the strength and number of the external magnetic fields were varying. VGs (vortex generators) were also installed to create vortex fields. A convective heat transfer coefficient was calculated to determine the heat transfer rate. In addition, the comparative analysis was performed with graphical results using contours of temperature and velocity.

Phase Behavior of Lyotropic Liquid-Crystalline Polymers under Varying Solvent Conditions: Effect of External Fields on the Phase Diagram.

In this work, we report a Density Functional Theory based study of phase behavior of lyotropic liquid-crystalline polymers under both good and varying solvent conditions in the presence of external electric or magnetic field. Our microscopic model for the good solvent case is based on the tangent hard-sphere chain with bond-bending potential to account for the chain stiffness; the variable solvent quality is modeled by adding attractive monomer-monomer interactions. The phase diagrams are constructed in three intensive variables (temperature, pressure, and field strength), and are characterized by the presence of critical and triple lines, which originate from the critical and triple points of the corresponding zero-field case. The merging of critical and triple lines results in the appearance of the "double critical" and "critical triple" points, already known from the earlier studies of the phase behavior of spin fluids in magnetic fields. The important difference of the present model from the spin fluids is due to the finite stiffness of the polymer chains (characterized by their persistence length), which adds an additional parameter controlling the morphology of the phase diagrams.

Research on the Density of Magnetic Fluid and its Application in Mineral Separation

The density of magnetic fluid is important for some applications such as mineral processing. Magnetic fluid is a nano-sized magnetic material which has superparamagnetism. The density of magnetic fluid with no magnetic field was introduced. The measuring method was studied and the calculating formula was deduced. Since magnetic fluid could be magnetized, it could be controlled by magnetic field. The density of magnetic fluid could be changed by magnetic field. The buoyancy of magnetic fluid in magnetic field was researched and it was concluded that the buoyancy force of magnetic fluid in magnetic field is related to the mass, the volume, the permeability, the magnetization of magnetic fluid and the gradient of magnetic field. For a certain magnetic fluid, the parameters of itself are fixed. Then the gradient of magnetic field is the mainly factor influencing the magnetic force. A density measuring method for magnetic fluid in magnetic field was introduced. A mineral separation device based on magnetic fluid was introduced. And the principle of the mineral separation device with magnetic fluid was studied. More kinds of magnetic fluid and applications could be explored by researching magnetic fluid.

Research on Magnetism and Magnetization Intensity of Magnetic Fluid

Magnetic fluid is a liquid magnetic material with high magnetization, fluidity and superparamagnetism. The composition and the performance of magnetic fluid in magnetic field were introduced. Magnetic model of magnetic fluid for application was established. Magnetic particles could be seen as magnetic needles with certain N-S directions whose direction could be controlled by external magnetic field. Magnetization mechanism of magnetic fluid was researched. Measurement principle of magnetization intensity was studied and the formulas were deduced. The working principle of vibrating sample magnetometer was introduced and the magnetization curve of magnetic fluid was measured and plotted. It was concluded that magnetic fluid has superparamagnetism which means that the remanence and coercivity of aggregation of magnetic fluid are both zero. Magnetism is an important characteristic of magnetic fluid for engineering applications that magnetic fluid with high magnetization intensity will be explored and researched.

Numerical Analysis of the Flow of a Casson Fluid in Magnetic Field over an Inclined Nonlinearly Stretching Surface with Velocity Slip in a Forchheimer Porous Medium

In this work, we have studied a magnetohydrodynamic, Casson fluid flow with velocity slip over an inclined nonlinearly stretching surface in Non-Darcy porous medium, numerically. In the mathematical model, we have transformed the momentum equation, energy equation and mass concentration equations to non-dimensional ordinary differential equations using similarity variables. We have solved the equations numerically by bvp4c using MATLAB for the numerical computation, and took and axes so that figures are clearly visible. We have discussed and analysed the magnitude of the velocity, temperature, concentration, Local Skin friction, Local Nusselt number and Local Sherwood number using their representative parameters and the effects of these parameters on the respective boundary layer regions using graphs, figures and tables.

MAGNETOCALORIC EFFECT AND HEAT CAPACITY OF MAGNETIC FLUIDS

The magnetic fluids based on magnetite nanoparticles were synthesized using mixed surfactants (oleic acid/alkenyl succinic anhydride) dispersed in different carrier media (polyethylsiloxane and dialkyldiphenyl). The physicochemical properties of magnetic fluids (density, viscosity, saturation magnetization, magnetic phase concentration, magnetic core size) were determined. Magnetic fluids are stable in a wide temperature range. All the samples of the magnetic fluids exhibit typical superparamagnetic behavior. The magnetocaloric effect and the specific heat capacity of the magnetic fluids were first direct determined at 288–350 K in a magnetic field of 0–1.0 T. The field dependences of the magnetocaloric effect have a classic linear form. The temperature dependences of the magnetocaloric effect of magnetic fluids in magnetic fields have an extreme character. Thermodynamic parameters of magnetic fluids (magnetization namely enthalpy/entropy change) were determined. The specific heat capacity of magnetic fluid samples in a zero magnetic field was obtained at different temperatures (at 278–350 K) on a differential scanning calorimeter and on the original microcalorimeter. The temperature dependences of the heat capacity of magnetic fluids in magnetic fields have an extreme character. It was established that the difference in heat capacity values obtained in and without the magnetic field is within the experimental error. The extreme character of the heat capacity is reflected in the magnetocaloric effect temperature dependences.

Transverse Magnetosonic Waves and Viscoelastic Resonance in a Two-Dimensional Highly Viscous Electron Fluid

In high-mobility materials, conduction electrons can form a viscous fluid at low temperatures. We demonstrate that in a high-frequency flow of a two-dimensional electron fluid in a magnetic field the two types of excitations can coexist: those of the shear stress (previously unknown transverse magnetosound) and those associated with the charge density (conventional magnetoplasmons). The dispersion law and the damping coefficient of transverse magnetosound originate from the time dispersion of the viscosity of the fluid. Both the viscoelastic and the plasmonic components of the flow exhibit the recently proposed viscoelastic resonance that is related to the own dynamics of shear stress of charged fluids in a magnetic field. We argue that the generation of transverse magnetosound, manifesting itself by the viscoelastic resonance, is apparently responsible for the peak in photoresistance and peculiarities in photovoltage observed in ultrahigh-mobility GaAs quantum wells.

Equations of Symmetric MHD-Boundary Layer of Viscous Fluid with Ladyzhenskaya Rheology Law

One considers flow past a body in an electrically conductive viscous fluid in magnetic field, the fluid being subject to a nonlinear rheological law. Solutions of the corresponding system of magnetohydrodynamic boundary layer are examined in a neighborhood of a frontal critical point.

Natural Frequency and Stability Tuning of Cantilevered CNTs Conveying Fluid in Magnetic Field

This paper investigates the dynamics of cantilevered CNTs conveying fluid in longitudinal magnetic field and presents the possibility of controlling/tuning the stability of the CNT system with the aid of magnetic field. The slender CNT is treated as an Euler-Bernoulli beam. Based on nonlocal elasticity theory, the equation of motion with consideration of magnetic field effect is developed. This partial differential equation is then discretized using the differential quadrature method (DQM). Numerical results show that the nonlocal small-scale parameter makes the fluid-conveying CNT more flexible and can shift the unstable mode in which flutter instability occurs first at sufficiently high flow velocity from one to another. More importantly, the addition of a longitudinal magnetic field leads to much richer dynamical behaviors of the CNT system. Indeed, the presence of longitudinal magnetic field can significantly affect the evolution of natural frequency of the dynamical system when the flow velocity is successively increased. With increasing magnetic field parameter, it is shown that the CNT system behaves stiffer and hence the critical flow velocity becomes higher. It is of particular interest that when the magnetic field parameter is equal to or larger than the flow velocity, the cantilevered CNT conveying fluid becomes unconditionally stable, indicating that the dynamic stability of the system can be controlled due to the presence of a longitudinal magnetic field.

The sedimentation of magneto-rheological fluid monitoring system based on resistivity measuring

The aim of the research was to determine the resistivity of magnetorheological fluid in magnetic field when sedimentation occurs. The resistivity was measured with special created device. Three sections of magnetorheological fluid contained in glass tube were measured: top of the fluid, the middle and the bottom. The resistivity of the fluid was measured when it was conditioning and after constant time intervals. The resistivity changing showed that the results were suitable to the procedure for estimating the sedimentation of magnetorheological fluids. DOI: http://dx.doi.org/10.5755/j01.mech.22.5.14958

Assessment of magnetic fluid stability in non-homogeneous magnetic field of a single-tooth magnetic fluid sealer

A special experimental stand has been developed and made to test magnetic fluid. It represents a single-tooth magnetic fluid sealer. The type of dependence of the pressure differential on magnetic fluid sealer operation time is used as a criterion to determine magnetic fluid stability and magnetic fluid sealer service life under such conditions. The siloxane-based magnetic fluid was used as the test sample. The colloidal stability as well as stability of the synthesized magnetic fluid in magnetic fields in static mode were determined. It has been found that the obtained magnetic fluid is stable in static mode and, consequently, can be used to conduct necessary tests on stand. Short-term and life tests on stand have shown that MF remains stable and efficient for at least 360 days of continuous utilization.

Issledovanie infrakrasnogo spektra pogloscheniya magnitnoy zhidkosti v magnitnom pole (kratkoe soobschenie)

Issledovanie infrakrasnogo spektra pogloscheniya magnitnoy zhidkosti v magnitnom pole (kratkoe soobschenie)

Relativistic gravity and parity-violating nonrelativistic effective field theories

We show that the relativistic gravity theory can offer a framework to formulate the non-relativistic effective field theory in a general coordinate invariant way. We focus on the parity violating case in 2+1 dimensions which is particularly appropriate for the study on quantum Hall effects and chiral superfluids. We discuss how the non-relativistic spacetime structure emerges from relativistic gravity. We present covariant maps and constraints that relate the field contents in the two theories, which also serve as the holographic dictionary in context of gauge/gravity duality. A low energy effective action for fractional quantum Hall states is constructed, which captures universal geometric properties and generates non-universal corrections systematically. We give another holographic example with dyonic black brane background to calculate thermodynamic and transport properties of strongly coupled non-relativistic fluids in magnetic field. In particular, by identifying the shift function in the gravity as minus of guiding center velocity, we obtain the Hall viscosity with its relation to Landau orbital angular momentum density proportional to Wen-Zee shift. Our formalism has a good projection to lowest Landau level.

A New Method for Measuring the Actuating Pressure of Magnetic Fluid in Magnetic Field

A New Method for Measuring the Actuating Pressure of Magnetic Fluid in Magnetic Field

THEORETICAL RESEARCH OF MECHANICAL BEHAVIOR OF MAGNETO-RHEOLOGICAL FLUID

This paper is intended to research of mechanical behaviour of magneto-rheological fluid in magnetic field. This liquid is with highly non-linear properties in magnetic field and their mechanical behaviour cannot be obtained directly. Additional pressure generated by magnetic field strength causes change of magneto-rheological fluid sur-face, therefore the system can be treated as mechanical. There is presented algorithm of evaluation of researched liquid additional pressure from magnetic field influence, which is caused by current in the solenoid. There is algo-rithm and method proposed how finite element method can be used to find additional pressure. The results of this solution give understanding of additional pressure characteristics of magneto-rheological fluid and possibility to use it for magnetically driven mechanical drive. Finally, conclusions on results are made. DOI: http://dx.doi.org/10.5755/j01.mech.19.5.5527

Computation method of magnetic fluid in strong magnetic field

When the magnetic fluid lays in the magnetic field, interaction effects exist between them. Thus, the precise computation is considered as one of the precise methods of analyzing magnetic fluid in the magnetic field. Comparing with it, the linear computation will bring more error. The more error exists between the decoupled computation and the linear computation, the more saturation magnetization does on the border. Besides, the value of magnetic flux density is bigger when using the decoupled computation than that of linear computation. What’s more, the equal magnetic flux density linear on the border varies slightly in the strong magnetic field when using the two computations. In a weaker magnetic field, the difference is bigger.