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Peristaltic flows of non-Newtonian fluids with heat and mass transfer have several applications in physiology and industry, which provide motivation for analysis of such flows. This article provides analysis of a two-dimensional peristaltic flow of a non-Newtonian fluid whose rheological characteristics are depicted by the Johnson–Segalman (J–S) model. Heat and mass transfer attributes considering heat generation/absorption and the Soret and Dufour effects are studied for present flow. A novel aspect of this study is Magnetohydrodynamics, accounting interactions between fluid and applied as well as induced magnetic fields based on of Maxwell's equations. Mathematical model incorporating such effects is then simplified using the lubrication approach. The resulting equations, adhering to no-slip conditions for velocity, temperature, and concentration, are solved numerically, and the graphical results are meticulously examined. The study reports significant findings and introduces a mechanism to obtain outcomes under the influence of a constant applied magnetic field at various stages, particularly within the scope of a low magnetic Reynolds number. The results indicate that by adjusting pertinent parameters, the behavior of a Newtonian fluid under hydrodynamic conditions can be replicated. In these conditions, the velocity of the Newtonian fluid surpasses that of the J–S fluid affected by the applied magnetic field. Furthermore, increasing the Hartman number diminishes the magnetic field's impact. Moreover, higher Reynolds numbers result in augmented current density near the midpoint of the channel, with larger Weissenberg and Hartman numbers resulting in a reduced trapped bolus size. [ABSTRACT FROM AUTHOR]

AbstractIn models of fluid dynamics, the magnetic field is essential for preserving the stability of flow streams and found applications in magnetic resonance imaging, magnetic levitation, and geophysical exploration. Recognizing the significance of this magnetic influence, we aim to investigate the behavior of flow within a three-dimensional squeezed film of Casson fluid situated between two rotating disks, under the influence of an induced magnetic field and the Reynolds viscosity model. The study also meticulously examines the heat and mass transfers, taking into account the effects of thermo-diffusion and diffusion-thermo. The resulting torque on both the upper and lower surfaces is analyzed and presented in a tabulated format. The normalized system of equations is transformed into a set of first-order differential equations, which are then solved using the bvp4c numerical solver in MATLAB. The impacts of various parameters are graphically illustrated in two different scenarios (ϒ=0.0,0.5), i.e., constant and variable viscosity. It is observed that when the variable viscosity parameter is set to zero, the azimuthal velocity profile experiences a more pronounced increase as the rotational parameter rises. Conversely, the azimuthal magnetic profile exhibits a more significant decrease when considering the influence of the variable viscosity parameter. Finally, the results are compared with previous studies in the literature for a limiting case, and error is reduced between 0.000003% and 0.000002%. [ABSTRACT FROM AUTHOR]

In this paper, we study the asymptotic behavior of the stationary 3D magneto-micropolar fluid flow through a thin domain, whose thickness is given by a parameter 0 < ε ≪ 1 . Assuming that the magnetic Reynolds number is written in terms of the thickness ε , we prove that there exists a critical magnetic Reynolds number, namely R e m c = ε - 2 , such that for every magnetic Reynolds number R e m with order smaller or equal than R e m c , the magneto-micropolar fluid flow in the thin domain can be modeled asymptotically when ε tends to zero by a 2D Reynolds-like model, whose expression is also given. [ABSTRACT FROM AUTHOR]

Spiral galaxies, including the Milky Way, have large-scale magnetic fields with significant energy densities. The dominant theory attributes these magnetic fields to a large-scale dynamo. We review the current status of dynamo theory and discuss various numerical simulations designed either to explain particular aspects of the problem or to reproduce galactic magnetic fields globally. Our main conclusions can be summarized as follows: Idealized direct numerical simulations produce mean magnetic fields, whose saturation energy density tends to decline with increasing magnetic Reynolds number. This is still an unsolved problem. Large-scale galactic magnetic fields of microgauss strengths can probably be explained only if helical magnetic fields of small or moderate length scales can be rapidly ejected or destroyed. Small-scale dynamos are important throughout a galaxy's life and probably provide strong seed fields at early stages. The circumgalactic medium (CGM) may play an important role in driving dynamo action at small and large length scales. These interactions between the galactic disk and the CGM may provide important insights into our understanding of galactic dynamos. We expect future research in galactic dynamos to focus on the cosmological history of galaxies and the interaction with the CGM as means of replacing the idealized boundary conditions used in earlier work. [ABSTRACT FROM AUTHOR]

Results of the numerical modeling of the nonstationary heat transfer and magnetic hydrodynamics of an electrically conducting liquid in a spherical layer have been presented. A study has been made of the influence of small values of the magnetic Reynolds number and the dissipation of Joule heat on the evolution of the structure of liquid flow, the temperature field, magnetic induction, and the distribution of Nusselt numbers. [ABSTRACT FROM AUTHOR]

We report the effects of an externally applied magnetic field on an electrically conducting fluid flow in a locally constricted channel. With the use of finite-difference discretization and the ADI (Alternating directions implicit) scheme, the non-linear coupled magnetohydrodynamic (MHD) equations in two dimensions were numerically solved. When the magnetic Reynolds number RM >> 1, an induced magnetic field forms in the motion and significantly affects flow. The electromagnetic force (Lorentz force) is developed and acts as a damping force. It results the suppression of flow separation regions developed due to the channel constrictions. It delays the onset of flow separation and the flow become stable. By employing suitable value of magnetic field one can completely suppress the flow separation. The induced magnetic field and current density vectors are dense at the constriction site due to high velocity shear in the downstream of the constriction, resulting in the creation of high shear magnetic and electric fields.

A torsional fatigue test of a torsion bar should be carried out in accordance with the nature of the real loads by applying cyclic loads created by a special test bench based on arc induction motors. This test bench uses the principle of resonant oscillation excitation and has a torsion bar spring pretension device, a massive flywheel (rotor), and a drive to create a sign-variable torque. As a mechanism for excitation of resonant oscillations of torsion bars, two arc stators are used that cover a massive flywheel (rotor) and are equipped with three-phase windings controlled by an electronic unit with a noncontact automatic control system on the basis of a starting thyristor device. The use of the resonant principle of oscillation excitation based on arc induction motors makes it possible to significantly simplify the existing design of the test bench and increase the efficiency when testing torsion bars. The developed functional diagram of the bench electric-drive control system provides automatic maintenance of the flywheel oscillations with a given accuracy during testing. These factors significantly increase the economic effect of the implementation of the test bench. [ABSTRACT FROM AUTHOR]

The permanent magnets will be irreversibly demagnetized under high temperature and high velocity during the electromagnetic buffering. In this study, the magnetic field induced by eddy currents and the self-demagnetizing field of permanent magnet are taken into consideration together for demagnetization analyse. The magnetic Reynolds number is used to express the eddy currents demagnetization. The correction coefficient being expressed as the index of the air-gap width, the inner cylinder thickness, iron pole axial length and the permanent magnet demagnetization coefficient is introduced by magnetic path analysis to represent the self-demagnetization effect and the demagnetization extent. The electromagnetic buffer (EMB) prototype is tested under intensive impact loads of different strengths at room temperature. The accuracy of the nonlinear irreversible demagnetization finite element model is verified by demagnetization on damping force, velocity and displacement. Finally, high-velocity demagnetization and high-temperature demagnetization are analysed in order to obtain the distribution law of irreversible demagnetization.

This paper deals with a mathematical model of a fluid flowing between two parallel plates in a porous medium under the influence of electromagnetic forces (EMF). The continuity, momentum, and energy equations were utilized to describe the flow. These equations were stated in their nondimensional forms and then processed numerically using the method of lines. Dimensionless velocity and temperature profiles were also investigated due to the impacts of assumed parameters in the relevant problem. Moreover, we investigated the effects of Reynolds number, Hartmann number M, magnetic Reynolds number, Prandtl number, Brinkman number ℱ, and Bouger number 𝜔, beside those of new physical quantities (N, ). We solved this system by creating a computer program using MATLAB. [ABSTRACT FROM AUTHOR]

The laminar, viscous and incompressible flow of an electrically conducting fluid across an unconfined wedge structure in the presence of a transverse magnetic field has been studied. Two-dimensional numerical simulations have been performed for Reynolds number (Re) = 1-150 and Hartmann number (Ha) = 0-10 for a fixed blockage ratio (ß) = d/W = 1/30. The magnetic induction method in magnetohydrodynamics module built in ANSYS FLUENT solver has been employed to compute the flow fields. Results show that the vortex shedding can be completely eliminated if the applied magnetic field is strong enough. In the steady flow regime, it has been found that the recirculation length reduces with the increase in Ha. A minimal reduction in the drag coefficient is observed with the increase in Ha as long as unsteady flow is maintained (Ha < 7.3). However, the drag coefficient has a tendency to significantly increase with the increase in Ha for steady flow. Similarly, the lift amplitude decreases with the increase in Ha indicating a diminishing effect on the strength of vortices. A critical Hartmann number (Hacr) of 7.3 has been found for Re = 100 at which complete suppression of vortex shedding is observed. [ABSTRACT FROM AUTHOR]

This paper investigates the damping and demagnetization effect of an electromagnetic buffer (EMB) under impact load. The motional eddy currents are calculated first, and the Ampere circuital theorem is employed to calculate the induced magnetic field. The demagnetization effect is formulated by the magnetic Reynolds number with a correction coefficient km. Following this, the time-step finite element (FE) model of the buffering system is constructed based on the nonlinear B–H curve. The accuracy and feasibility of the FE model is preliminarily verified by small-scale impact test. The characteristics of damping displacement, velocity, damping force and damping coefficient are obtained. Then, the demagnetization effect is analysed by eddy current, magnetic field distribution, through the intensive impact load test at room temperature and time-step FE model. The value of km is obtained through the intensive impact test and the simplified expression of critical velocity. The results show that the demagnetization effect is obvious with the increase of velocity. By introducing the correction coefficient of magnetic Reynolds number, the eddy current demagnetization process is more realistic. [ABSTRACT FROM AUTHOR]

In this study the effect of magnetic Reynolds number variation on magnetic distribution of natural convection heat transfer in an enclosure is numerically investigated. The geometry is a two dimensional enclosure which the left wall is hot, the right wall is cold and the top and bottom walls are adiabatic. Fluid is molten sodium with Pr=0.01 and natural convection heat transfer for Rayleigh number, Ra=105 , and magnetic Reynolds numbers 10-1, 10-3 and 10-5 are considered and the governing equations including continuum, momentum, energy and magnetic induction are solved together concurrent. The numerical method finite volume and simpler algorithm for coupling the velocity and pressure is used. The results show for high magnetic Reynolds number the non-dimensional magnetic field in X and Y directions approximately are constant because diffusion of magnetic Reynolds number is more than advection but as magnetic Reynolds number increases the magnetic field in enclosure is not equal to applied magnetic field and is not constant and deviation from one is increased so that for Rem=10-1 the non-dimensional magnetic field in X direction from 0.09 to 6.6 and in Y direction from -1.164 to 4.05 changes.

In this study, the electrically conducting fluid flow inside a channel with local symmetric constrictions, in the presence of a uniform transverse magnetic field is investigated using Lattice Boltzmann Method (LBM). To simulate Magnetohydrodynamics (MHD) flow, the extended model of D2Q9 for MHD has been used. In this model, the magnetic induction equation is solved in a similar manner to hydrodynamic flow field which is easy for programming. This extended model has a capability of simultaneously solving both magnetic and hydrodynamic fields; so that, it is possible to simulate MHD flow for various magnetic Reynolds number (Rem). Moreover, the effects of Rem on the flow characteristics are investigated. It is observed that, an increase in Rem, while keeping the Hartman number (Ha) constant, can control the separation zone; furthermore, comparing to increasing Ha, it doesn't result in a significant pressure drop along the channel.

We consider the classical problem of Magnetohydrodynamic (MHD) flow past a circular cylinder in the presence of an imposed magnetic field aligned to the flow. Our analysis includes the computation of magnetic field in the interior of the cylinder because in an experimental setup, the magnetic field will naturally pass through the cylinder. As such, we have solved the Maxwell's equations both in the fluid flow region as well as in the interior of the cylinder with appropriate continuity conditions for magnetic field as it penetrates the cylinder. The fully nonlinear MHD equations are solved numerically using a highly accurate finite difference scheme. The influence of magnetic field in controlling boundary layer separation is discussed through the analysis of pressure gradient and the radial and transverse velocity gradients. In fact, magnetic field penetrated inside the cylinder helps to suppress flow separation more effectively than otherwise. A non-monotonic behavior of interaction parameter on the flow separation is observed for low values of magnetic Reynolds numbers (R m). Most importantly, we examine the realm of Quasi-Static approximation in the two-dimensional MHD flows against the corresponding computationally expensive fully nonlinear MHD solutions. Our results suggest that even if R m = 0. 5 , the percentage error in using Quasi-Static approximation can reach up to 17.5%. Thus we have analyzed and quantified the differences between the fully nonlinear treatment and the Quasi-Static approximation for this classical flow configuration for the first time. [ABSTRACT FROM AUTHOR]

As part of the EU New Horizon 2020 project on a Magnetohydrodynamic (MHD) Enhanced Entry System for Space Transportation (MEESST) superconducting magnetic coils will be exposed within an MHD probe to a high enthalpy air plasma. This study assesses key parameters for MHD flow manipulation experiments with the aid of emission spectroscopy measurements of high enthalpy air plasma flows. Thus, the electric conductivity of the plasma and the respective experimental Stuart number and magnetic Reynolds number are derived and compared to literature. The results show that the Lorentz forces are dominating the viscous and inertia forces of the plasma flow by orders of magnitude. When the MHD probe will be exposed to the investigated plasma flow, a significant MHD effect should be observable. • Successful assessment of MHD flow parameters in high enthalpy air plasma. • Accounting for Hall effects is crucial in MHD flow manipulation experiments. • Significant MHD effect expected when introducing probe to high enthalpy air plasma. [ABSTRACT FROM AUTHOR]

We investigate the influence of the magnetic Reynolds number Rem on the signal from electrodes in an the electromagnetic flowmeter. Conditions for eliminating this dependence by applying an inhomogeneous magnetic field, several pairs of electrodes, and a numerical integration algorithm are considered. We demonstrate the possibility of calibrating the flowmeter using a low-capacity liquid-metal flow fixture. [ABSTRACT FROM AUTHOR]

In this study, the electrically conducting fluid flow inside a channel with local symmetric constrictions, in the presence of a uniform transverse magnetic field is investigated using Lattice Boltzmann Method (LBM). To simulate Magnetohydrodynamics (MHD) flow, the extended model of D2Q9 for MHD has been used. In this model, the magnetic induction equation is solved in a similar manner to hydrodynamic flow field which is easy for programming. This extended model has a capability of simultaneously solving both magnetic and hydrodynamic fields; so that, it is possible to simulate MHD flow for various magnetic Reynolds number (Rem). Moreover, the effects of Rem on the flow characteristics are investigated. It is observed that, an increase in Rem, while keeping the Hartman number (Ha) constant, can control the separation zone; furthermore, comparing to increasing Ha, it doesn't result in a significant pressure drop along the channel. [ABSTRACT FROM AUTHOR]

Lyapunov direct method has been used to study the nonlinear stability of laminar flow between two parallel planes in the presence of a coplanar magnetic field for streamwise perturbations with stress-free boundary planes. Two Lyapunov functions are defined. By means of the first, it is proved that the transverse components of the perturbations decay unconditionally and asymptotically to zero for all Reynolds numbers and magnetic Reynolds numbers. By means of the second, it is showed that the other components of the perturbations decay conditionally and exponentially to zero for all Reynolds numbers and the magnetic Reynolds numbers below $$\frac{\pi ^2}{2M}$$ , where M is the maximum of the absolute value of the velocity field of the laminar flow. [ABSTRACT FROM AUTHOR]