Uniform Transverse Magnetic Field Research Articles

Hexagonal warping effects on Bloch oscillations in proximitized Rashba systems

Bloch oscillations (BOs) in Rashba systems, taking into account the effects of hexagonal warping and proximity-induced band gap, are reported. We find that in addition to real-space trajectories, the group and Berry velocities of Bloch electrons exhibit novel BOs which strongly depend on the crystal momentum. This oscillatory motion is affected significantly by variations in the strength of hexagonal warping and the proximity-induced band gap, originating from the substantial changes in the energy spectrum induced by these factors. In addition, it is shown that the Bloch oscillations are modified considerably under the influence of applied uniform in-plane electric and transverse magnetic fields, which allow for a geometric visualization of the Bloch dynamics. Interestingly, when the system is subjected to these fields simultaneously, it undergoes a dynamic phase transition between confined and de-confined states. This phase transition is tuned by the relative strength of the applied fields and is further influenced by variations in the strength of hexagonal warping and proximity-induced band gap. The appearance of such a transition is attributed to the interplay between the external fields and the intrinsic properties of the crystal lattice. Moreover, we find that the direct-current drift velocity shows negative differential conductivity, which is a characteristic feature of the BO regime.

Laminar convective heat transfer combining buoyancy and thermal radiation of Carreau fluid within a concentric and eccentric annulus

The present study concerns a steady-state laminar combined thermal radiation and buoyancy-driven conjugate magnetohydrodynamic (MHD) natural convective flow and heat transfer inside a fully porous medium eccentric circular annulus bounded by two infinite horizontal cylinders occupied by a Carreau fluid permeated by a uniform transverse magnetic field (B0 ) and inclined by an angle (α). The convective and thermal radiation are approximated by the Boussinesq and Roseland models, respectively. The numerical integration was performed using the implicit finite volume method. The convective terms in the momentum and energy equations were Discretized using the second-order upwind method. On the other hand, the diffusive terms were Discretized using the central difference scheme. The pressure-velocity coupling was solved using the SIMPLE approach. The findings suggest a clear trend of enhancement in the heat transfer rate when the aspect ratio and annulus eccentricity increase. This pattern is more pronounced in the negative vertical eccentricities. It is worth noting that the eccentric annulus, which has an annulus aspect ratio of 1.6 and a vertical eccentricity of −0.8, offers the best performance regarding the heat transfer mechanism inside the annulus gap. The heat transfer mechanism turns out to be strongly affected by thermal radiation, Hartmann number, and magnetic field inclination angle. The increased thermal radiation parameter and the decreased flow behavior index improve the heat transfer mechanism between the Carreau fluid and the inner cylinder in the annular gap. Furthermore, the average Nusselt number increases considerably as the induced magnetic field inclines.

Influence of plasticity on the magnetic-field-induced bending deformation in a magneto-active elastomer with superparamagnetic nanoparticles

The influence of residual plastic deformation on the bending deformation of a magnetoactive elastomer (MAE) beam with non-coercive superparamagnetic manganite (La0.6Ag0.2Mn1.2O3) nanoparticles induced by a transverse uniform magnetic field has been studied. It was found that the MAE bending induced by the magnetic field switching-on/switching-off is mainly cyclic elastic. Plastic deformation leads to the emergence of residual bending and hysteresis in the field dependence of the bending. It was shown that the residual bending that appears after the first magnetic field switch-on eliminates the uncertainty of the bending direction at the next magnetization. Due to the residual plastic deformation, the bending direction of the superparamagnetic MAE with nanoparticles does not change when the direction of the applied magnetic field is inverted, in contrast to the MAE with microparticles where the uncertainty of the bending direction is eliminated due to the residual magnetization of weakly coercive ferromagnetic microparticles; therefore, the bending direction changes its sign with magnetic field reversion. In the low fields, the bending value for the MAEs with superparamagnetic particles is proportional to the square of the magnetic field strength. Model estimates on the residual deformation influence on the beam bending at beam magnetization reversal were obtained.

The Onset of Instability in A Magnetohydrodynamic Channel Flow through Porous Media of Casson Fluid

A detailed study is made on the stability of linear two-dimensional disturbances of Plane Poiseuille Flow (PPF) of Casson fluid through porous media in the presence of a vertical uniform magnetic field, B0 which is extremely useful in metals, mines, and fuels industries. Using the method of normal modes, the disturbance equations are derived. The resulting eigenvalue problem is then solved by the spectral collocation method using Chebyshev-based polynomials. The critical values of the triplets ( Rec, αc, cc ) are obtained for various values of the Casson parameter, η , Hartmann number, Ha , and porous parameter, σp. The stability of the system is discussed using the neutral stability curves for each value of the parameters present in the problem. It is found that the stability regions are enlarged for small values of η and large values of the porous parameter, σp and Hartmann number, Ha. It is also observed that the stability characteristics of plane Poiseuille flow in a porous medium are remarkably different from non-porous cases. The results obtained here contribute to the contemporary efforts to better understand the stability characteristics of PPF of Casson fluid flow through porous media in the presence of a uniform transverse magnetic field.

Electromagnetohydrodynamic (EMHD) convective transport of a reactive dissipative carreau fluid with thermal ignition in a non-Darcian vertical duct

A mathematical model is developed to simulate the steady, laminar exothermic reactive electromagneto-hydrodynamic combustible non-Newtonian natural convective transport in a vertical duct. Static uniform axial electrical field and transverse magnetic field are imposed. The Frank-Kamenetskii thermal explosion theory is utilized and also the Carreau fluid model, the latter due to its ability to simulate shear-thinning, Newtonian and shear-thickening behaviour. The duct contains a homogenous, isotropic porous medium and to accomodate Forchheimer inertial drag effects, a non-Darcian model is deployed. The duct walls are permeable enabling suction and injection effects to be studied. Viscous and Joule heating (Ohmic dissipation) are also featured in the model. Following a scaling transformation, the dimensionless emerging non-linear ordinary differential boundary value problem is solved with a robust numerical method (Mathematica shooting algorithm). Validation with an Adomian decomposition method (ADM) is included.

Magnetohydrodynamic Couette flow of alumina–water nanofluid over a deformable porous channel under uniform transverse magnetic field with entropy optimisation

The present study is concerned about magnetohydrodynamic Couette flow of nanofluid with entropy analysis in the presence of injection and suction over a deformable permeable channel containing nanoparticles of alumina (Al2O3). The influences of non-linear thermal radiation and activation energy are considered. The leading partial differential equations are simplified to non-linear ordinary differential equations by applying appropriate similarity transformation. The simplified governing equations are solved by utilising MATLAB bvp4c finite difference technique. Here, we observed the behaviour of various physical parameters on solid displacement, temperature, velocity, concentration, entropy generation, Bejan number and skin friction. Observation reflects that drag parameter enhances solid displacement, while reduces fluid velocity, and a significant behaviour is seen in skin friction. Radiation parameter and chemical reaction parameter diminish the fluid temperature and concentration, respectively. Moreover, volume fraction parameter reflects some significant behaviour for entropy generation number and Bejan number. Rate of heat transfer enhances due to the raising of radiation parameter. Fluid flow through a deformable porous regime established by biological applications such as study on articular cartilage, artery walls, skin, soft tissue and so on.

Thermal Performance of Autocatalytic Chemical Reaction for Hybrid Nanomaterial Fluid Flow

The mass and heat transfer in hybrid magnetohydrodynamic (MHD) nanofluids is controlled by an autocatalytic chemical mechanism, which is the subject of the current study's thorough analysis. The focus of the work is on the nanolayers at interfaces, which link nanoparticles with the supporting fluids and enable coupled mass and heat transfer phenomena.To further investigate its effects, a uniform transverse magnetic field is added to the study.By using similarity methods, the governing nonlinear coupled partial differential equation that describes this sophisticated system is converted into a collection of ordinary differential equations (ODEs). Two numerical approaches( Bvp4c) and the Shooting method, are used to solve the ODEs in order to get precise answers and do a comparison study. One interesting finding about the improvement of thermal performance is that a rise in nanolayer thickness (between 1 and 4) considerably adds to the enhancement. Additionally, it is discovered that improvements in the chemical reaction parameter, which ranges from 0.15 to 0.27, cause the Sherwood number to rise.It is noteworthy that the results of this study add to a better understanding of the complex interactions between magnetohydrodynamics, chemical processes, and nanofluid dynamics. The numerical techniques used highlight the significance of accurate mathematical modeling in illuminating the complexity of such systems. In addition to strengthening the theoretical foundation, this study offers useful information that could have an impact on heat transfer and nanofluid technology applications.

Heat transfer and entropy generation on mixed convection hydromagnetic slip-flow in a channel filled with porous medium: Adomian decomposition approach

This study analyses the heat transfer and entropy generation on mixed convection hydromagnetic fluid flow in a permeable parallel wall vertical channel; filled with an optically thick and electrically conducting liquid permeated by a uniform transverse magnetic field. The study considers the nonlinearity in thermal radiation, the irregular thermal heat produced/consumed, and the slipperiness and mass flux at the walls. The nonlinear coupled governing partial differential equations are reduced to ordinary dimensionless types. The Adomian Decomposition Method (ADM) is applied to solve the emerging boundary value problem. Comparisons are made for some basic emergent scientific parameters using the evaluated values of the velocity and temperature profiles for ADM and numerical algorithm (RKF 4-5) in the Maple, and the results are impressive. Entropy generation numbers are computed through the Bejan formulation. The results are presented for the velocity, temperature and entropy generation profiles and discussed quantitatively. Amongst others, it is perceived that velocity increases with heat generation and suction-based parameters while entropy generation surges consequentially to the improved Grashof and Darcy numbers in the entirety of the flow regime. This study finds applications in modern engineering systems for energy loss control, frequently encountered in the manufacturing, nuclear energy and processing industries.

Influence of Dofour and Soret on Eyrig-Powell Nanofluid Flow from A Circular Cylinder with Viscous Dissipation

The impact of Viscous dissipation on the heat and mass transfer characteristics of an Eyring Powell nanofluid flow past a horizontal circular cylinder is intensively investigated in the presence of Dufour and Soret effects. The free laminar flow is subject to a uniform transverse magnetic field. The continuity, momentum, energy, and concentrations equations are transformed into a nonlinear system of partial differential equations using appropriate non-similarity variables. The transformed system was solved numerically using the fourth order Runge Kutta method. The effect of parameters including Prandtl number, Dufour effect, Soret effect and Schmidt number were studied and presented graphically. Nusselt and Sherwood numbers have also been derived and discussed numerically.

Quantum-information theory of magnetic field influence on circular dots with different boundary conditions

Influence of the transverse uniform magnetic field B on position (subscript ρ) and momentum (γ) Shannon quantum-information entropies S ρ,γ Fisher informations I ρ,γ and informational energies O ρ,γ is studied theoretically for the 2D circular quantum dots (QDs) whose circumference supports homogeneous either Dirichlet or Neumann boundary condition (BC). Comparative analysis reveals similarities and differences of the influence on the properties of the structure of the surface interaction with the magnetic field. A conspicuous distinction between the two spectra are crossings at the increasing induction of the Neumann energies with the same radial quantum number n and adjacent non-positive angular indices m. At the growing B, either system undergoes Landau condensation when its characteristics turn into their uniform field counterparts. It is shown that for the Dirichlet system this transformation takes place at the smaller magnetic intensities; e.g. the Dirichlet sum on its approach from above to a fundamental limit is at any B smaller than the corresponding Neumann quantity what physically means that the former geometry provides more total information about the position and motion of the particle. It is pointed out that the widely accepted disequilibrium uncertainty relation , with d being a dimensionality of the system, is violated by the Neumann QD in the magnetic field. Comparison with electrostatic harmonic confinement is performed; in particular, contrary to the hard-wall QDs, for this configuration the sums S ρ + S γ and the products I ρ I γ and O ρ O γ do not depend on the field. Physical interpretation is based on the different roles of the two BCs and their interplay with the field: Dirichlet (Neumann) surface is a repulsive (attractive) interface.

Numerical study on the flow and heat transfer of molten salt in a horizontal pipe applied transverse magnetic field

Based on a modification of a magnetohydrodynamic turbulence model, a numerical study was performed to investigate the effects of transverse uniform and gradient magnetic field on the turbulent flow and heat transfer characteristics of a low melting point molten salt in a stainless steel pipe. With the Hartmann number from 0 to 80, the numerical results showed that the fluid flow displayed anisotropic distributions under the magnetic field with decrease of velocity in the mainstream region, and decrease of turbulent intensity, whereas the flow velocity increased in the boundary layer near the Hartmann and Roberts wall. Especially, a velocity jet phenomenon was observed in the Roberts boundary layers at higher Hartmann number in the uniform magnetic field or the positive gradient magnetic field. Under the gradient magnetic field, the flow and heat transfer of molten salt displayed much more variations than under the uniform magnetic field. The magnetohydrodynamic calculation results proposed here might be helpful to the design of the composite heat transfer system for molten salt in actual industrial applications.

Spontaneous change of symmetry in a magnetoactive elastomer beam at its critical bending induced by a magnetic field

The features of the critical bending deformation and magnetization of a magnetoactive elastomer (MAE) beam with a fixed end in a transverse uniform magnetic field have been studied. After the beam reaches a critical bending, the symmetry of the beam shape and the symmetry of the MAE magnetic state change spontaneously. At the critical point, a continuous transition from the highly symmetric magnetic state in the unbent MAE beam to the low symmetric magnetic state in the bent MAE beam (this is the angular state with the effective magnetization inclined to the field) takes place. The beam bending occurs due to the gain in the magnetic energy of the beam. The formation of an angular magnetic state in it has a magnetoelastic origin and is characterized by the critical behavior of the mutually related bending and longitudinal effective magnetization of the MAE, but it is the magnetization that plays the role of order parameter. Furthermore, there is no longitudinal magnetization in the absence of bending and, vice versa, there is no bending in the absence of longitudinal magnetization. The influence of a low remanent magnetization, which eliminates the uncertainty in the bending direction, on the critical bending has been analyzed. The role of the magnetorheological effect, which affects the critical field magnitude and leads to the appearance of field-induced bending hysteresis near the critical point, has also been elucidated.

Computational analysis of conductive fluid flow with tangential components of magnetic flux density and electric field in metallic and non-metallic circular pipe

This paper has focused on the study of flow characteristics of a steady conductive fluid through a circular pipe in the presence of an applied transverse uniform magnetic field. A numerical simulation of the fluid flow was performed using a multi-physics computational tool. The radial velocity distribution due to the effect of the tangential component of induced magnetic flux density and electric fields at various axial positions is examined in metallic and non-metallic surfaces of the circular pipe. This simulation study helps to analyse the effect of drag force on the variation in axial velocity close to the metallic and non-metallic walls. The induced electric potential is directed along the normal to the Laplacian tangential surface of the pipe. In addition to that, sigmoidal-shaped field profiles are observed when the fluid flow crosses from the upstream to downstream of the magnet edge and vice versa along the axial length of the circular pipe. Simultaneously, it is observed that the average velocity of the fluid flow decreases for a laminar and increases for turbulent Reynolds number. Streamline plots pertinent flow variable such as flow velocity are presented for non-conducting and conducting walls.

Unsteady Magnetohydrodynamics (MHD) Natural Convective Flow of Nanofluids Over an Infinite Perpendicular Absorbent Plate

The magnetic fields played the significant roles in plentiful field they are, biologically, chemically, mechanically as well as medically all investigations. In clinical as well as medical investigation the magnets were extremely imperative to create 3-dimensional images of anatomical as well as diagnostics significance from nuclear magnetic resonances signal. In views of those applications, the purpose of present research is to the unsteady MHD convective flow past a moving vertical porous plate in nanofluids in the presence of a uniform transverse magnetic field has been carried out. The governing equations are solved using Laplace transform technique and the solutions are presented in closed form. The numerical computations of velocity and nanofluid temperature the rate of heat transfer and the shear stress at the plate are presented graphically for several values of the pertinent parameters. An increase in radiation parameter leads to decrease the fluid velocity as well as temperature in the boundary layer region. The velocity enhances with increasing permeability parameter. An increase in Grashof number and an increase in time lead to increase the fluid temperature. The rate of heat transfer at the plate is found to be higher for Cu-water nanofluid. The shear stress at the plate for Cu-water nanofluid is found to be lower. The present study has many applications in engineering devices.

Impact of couple stress and variable viscosity on heat transfer and flow between two parallel plates in conducting field

<abstract> <p>This study explores the flow properties of a couple stress fluid with the consideration of variable viscosity and a uniform transverse magnetic field. Under the effect of irreversible heat transfer, a steady fluid flow has taken place between two parallel inclined plates. The fluid flows due to gravity and the constant pressure gradient force. The plates are fixed and isothermal. The governing equations have been solved analytically for velocity and temperature fields. The total rate of heat flow and volume flow across the channel, skin friction, and Nusselt number at both plates are calculated and represent the impacts of relevant parameters through tables and graphs. The findings show that velocity, temperature, and the total rate of heat flow across the channel are enhanced by increasing the couple stress parameter and the viscosity variation parameter, while increasing the values of the Hartmann number reduces them.</p> </abstract>

Two layer thin film flow over a stretching sheet with uniform transverse magnetic field

The objective of the present work is to study the effect of uniform transverse magnetic field on two immiscible thin liquid film flow over a linear stretching sheet. Applying similarity transformations, the guiding Navier–Stokes equations have been transformed into a system of non-linear partial differential equations, which are numerically solved by the finite difference method. The effects of the governing parameters viz. magnetic field parameter Mn, density ratio m, viscosity ratio n, thickness ratio δ and Reynolds number Re1 are analyzed in detail. It is found that the effect of varying Reynolds number is more pronounced on film thinning in presence of uniform transverse magnetic field.

MHD convective rotating flow of viscoelastic fluid past an infinite vertical oscillating porous plate with Hall effects

AbstractIt is considered the unsteady and incompressible magnetohydrodynamic rotating free convection flow of viscoelastic fluid with simultaneous heat and mass transfer near an infinite vertical oscillating porous plate under the influence of uniform transverse magnetic field and taking Hall current into account. The governing equations of the flow field are then solved by a regular perturbation method for a small elastic parameter. The expressions for the velocity, temperature, and concentration have been derived analytically and also its behavior is computationally discussed with reference to different flow parameters with the help of graphs. The skin friction on the boundary, the heat flux in terms of the Nusselt number, and the rate of mass transfer in terms of the Sherwood number are also obtained and their behavior discussed. The resultant velocity enhances with increasing Hall parameter and rotation parameter. The reversal behavior is observed with increasing viscoelastic parameters. The resultant velocity enhances and experiences retardation in the flow field with increasing radiation parameters, whereas the secondary velocity component increases with increasing rotation parameters. The temperature diminishes as the Prandtl number and/or the frequency of oscillations. The concentration reduces at all points of the flow field with the increase in the Schmidt number.

Steady-State Solutions for MHD Motions of Burgers’ Fluids through Porous Media with Differential Expressions of Shear on Boundary and Applications

Steady-state solutions for two mixed initial-boundary value problems are provided. They describe isothermal MHD steady-state motions of incompressible Burgers’ fluids over an infinite flat plate embedded in a porous medium when differential expressions of shear stress are given on a part of the boundary. The fluid is electrically conductive under the influence of a uniform transverse magnetic field. For the validation of the results, the expressions of the obtained solutions are presented in different forms and their equivalence is graphically proved. All of the obtained results could easily be particularized to give exact solutions for the incompressible Oldroyd-B, Maxwell, second-grade, and Newtonian fluids that were performing similar motions. For illustration, the solutions corresponding to Newtonian fluids are provided. In addition, as an application, the velocity fields were used to determine the time required to reach the steady or permanent state for distinct values of magnetic and porous parameters. We found that this time declined with increasing values of the magnetic or porous parameters. Consequently, the steady state for such motions of Burgers’ fluids was earlier reached in the presence of a magnetic field or porous medium.

Impact of thermal diffusion and chemical reaction on oscillatory MHD convective flow of a viscoelastic fluid through a porous medium in a slip flow regime

AbstractThe purpose of the current investigation is to analyze the influence of thermal diffusion on magnetohydrodynamic viscoelastic fluid flow with concurrent heat and mass transfer near an oscillating porous plate in a slip flow Regime under the influence of a uniform transverse magnetic field. The uniqueness of the present study is to examine the effects of viscoelastic property (Walters B' model) on the flow and heat transfer phenomena when a transverse magnetic field and time‐dependent fluctuating suction at the boundary surface are present in a porous medium with a uniform porous matrix. A regular perturbation technique is used to solve the governing equations for small elastic parameters. Graphical representations are used to show how different parameters affect skin friction, temperature, concentration, and velocity. It is observed that concentration distribution as well as the coefficient of friction is enhanced due to the thermal diffusion effect. It is noticed that the visco‐elastic parameters reduce the velocity of the fluid. In addition, chemical reactions and suction factors cause the flow field's temperature to drop. Furthermore, the fluid concentration drops under the chemical reaction effect.

Heat transport analysis in buoyancy-driven flow of Maxwell fluid induced by a vertically stretching sheet inspired by Cattaneo Christov theory

We used non-Fourier's approach to model the heat transfer equations in magneto-hydrodynamic Maxwell nanofluid flow due to vertical stretching sheet under the influence of buoyancy force. The impact of uniform transverse magnetic field is also considered. This problem is analyzed with two heating processes: constant wall temperature (CWT) and prescribed surface temperature (PST). The heat and mass transport features are explored by implementing the modified Fourier's and Fick's laws.The governing equations are transformed into ordinary differential equations (ODEs) through appropriate similarity transformations. The resulting equations are solved numerically using the bvp4c program in MATLAB. The impact of physical parameter on the velocity, thermal, and solutal distributions is discussed in detail and presented graphically for aiding the flow. In this study, the velocity boosts unsteadiness parameter and thermal buoyancy parameter. Both velocity and temperature behave in opposite ways when affected by a magnetic field. Moreover, the building strength of the thermal relaxation time parameter does not escalate the thermal transport.