Magnetic Field Of Uniform Strength Research Articles

MHD free convective flow through porous medium in the presence of hall current, radiation and thermal diffusion

An unsteady free convective flow through porous media of viscous, incompressible, electrically conducting fluid through a vertical porous channel with thermal radiation is studied. A magnetic field of uniform strength is applied perpendicular to the vertical channel. The magnetic Reynolds number is assumed very small so that the induced magnetic field effect is negligible. The injection and suction velocity at both plates is constant and is given by v0. The pressure gradient in the channel varies periodically with time along the axis of the channel. The temperature difference of the plates is high enough to induce the radiative heat. Taking Hall current and Soret effect into account, equations of motion, energy, and concentration are solved. The effects of the various parameters, entering into the problem, on velocity, temperature and concentration field are shown graphically.

Effects of heat absorption and chemical reaction on a three dimensional MHD convective flow past a porous plate

An attempt has been made to investigate the effects of heat sink and chemical reaction on a three dimensional Magneto hydrodynamics (MHD) convective flow with mass transfer of an incompressible viscous electrically conducting fluid past a porous vertical plate with transverse sinusoidal suction velocity. A magnetic field of uniform strength is assumed to be applied transversely to the direction of the main flow. The magnetic Reynolds number is considered to be small that induced magnetic field can be neglected. The governing equations are solved by regular perturbation technique. The expression for velocity field, temperature field, species concentration, current density, the skin friction, Nusselt number and Sherwood number at the plate are obtained in non dimensional forms. The effect of Hartman number, chemical reaction parameter, heat sink parameter on the velocity field, zeroth order skin friction and the amplitude of the first order skin friction, first order Nusselt number and the first order Sherwood number at the plate are discussed graphically. It is seen that chemical reaction and heat sink have significant effects on the flow and on the heat and mass transfer characteristics. Key words: Three-dimensional convective flow, heat transfer, incompressible viscous fluid, wall shear stress, heat sink.

Magnetohydrodynamics and Radiation Effects on the Flow due to Moving Vertical Porous Plate with Variable Temperature

The combined effects of magnetohydrodynamics and thermal radiations on unsteady flow of an electrically conducting fluid past an impulsively started infinite vertical porous plate with variable temperature is investigated. A magnetic field of uniform strength is applied along an axis perpendicular to the plate. The plate temperature is raised linearly with time. An exact solution is obtained by Laplace transformation technique. The dependence of the amplitude of velocity and skin-friction on various parameters are discussed in detail with the help of graphs.

Exact Solution Of MHD Mixed Convection Periodic Flow In A Rotating Vertical Channel With Heat Radiation

Magnetohydrodynamic (MHD) mixed convection flow of a viscous, incompressible and electrically conducting fluid in a vertical channel is analyzed analytically. A magnetic field of uniform strength is applied perpendicular to the planes of the channel walls. The fluid is acted upon by a periodic variation of the pressure gradient in the vertically upward direction. The temperature of one of the plates is non-uniform and the temperature difference of the walls of the channel is high enough to induce heat transfer due to radiation. The fluid and the channel rotate in unison with an angular velocity about the axis normal to the plates of the channel. An exact analytical solution of the problem is obtained. Two cases of small and large rotation have been considered to assess the effects of different parameters involved in the flow problem. The velocity field, the amplitude and the phase angle of the shear stress are shown graphically and discussed in detail. During analysis it is found that the flow problem studied by Makinde and Mhone (2005) is incorrect physically and mathematically

Corrigendum to “Heat and Mass Transfer Effect on MHD Flow of a Viscoelastic Fluid through a Porous Medium Bounded by an Oscillating Porous Plate in Slip Flow Regime”

Unsteady flow of an eclectically conducting and incompressible viscoelastic liquid of the Walter model with simultaneous heat and mass transfer near an oscillating porous plate in slip flow regime under the influence of a transverse magnetic field of uniform strength is presented. The governing equations of the flow field are solved by a regular perturbation method for small elastic parameter, and the expressions for the velocity, temperature, concentration, skin friction , the heat flux in terms of the Nusselt number , and the rate of mass transfer in terms of the Sherwood number are obtained. The effects of the important flow parameters on the dynamics are discussed. Findings of the study reveal that the rarefaction parameter accelerates the fluid particles in the flow domain. Elastic parameter contributes to sudden fall of the velocity near the plate. Magnetic force contributes to greater skin friction as the time elapses. Destructive reaction reduces, whereas generative reaction enhances the concentration distribution.

MHD Mass Transfer Flow past a Vertical Porous Plate Embedded in a Porous Medium in a Slip Flow Regime with Thermal Radiation and Chemical Reaction

This problem presents the effects of thermal radiation and chemical reaction on MHD unsteady mass transfer flow past a semi-infinite vertical porous plate embedded in a porous medium in a slip flow regime with variable suction. A magnetic field of uniform strength is assumed to be applied transversely to the direction of the main flow. Perturbation technique is applied to transform the non-linear coupled governing partial differential equations in dimensionless form into a system of ordinary differential equations. The resulting equations are solved analytically and the solutions for the velocity, temperature and concentration fields are obtained. The effects of various flow parameters on velocity, temperature and concentration fields are presented graphically. For different values of the flow parameters involved in the problem, the numerical calculations for the Nusselt number, Sherwood number and skin-friction co-efficient at the plate are performed in tabulated form. It is seen that chemical reaction causes the velocity field and concentration field to decrease and the chemical reaction decreases the rate of viscous drag at the plate.

Heat and Mass Transfer Effect on MHD Flow of a Viscoelastic Fluid through a Porous Medium Bounded by an Oscillating Porous Plate in Slip Flow Regime

Unsteady flow of an eclectically conducting and incompressible viscoelastic liquid of the Walter model with simultaneous heat and mass transfer near an oscillating porous plate in slip flow regime under the influence of a transverse magnetic field of uniform strength is presented. The governing equations of the flow field are solved by a regular perturbation method for small elastic parameter, and the expressions for the velocity, temperature, concentration, skin friction , the heat flux in terms of the Nusselt number , and the rate of mass transfer in terms of the Sherwood number are obtained. The effects of the important flow parameters on the dynamics are discussed. Findings of the study reveal that the rarefaction parameter accelerates the fluid particles in the flow domain. Elastic parameter contributes to sudden fall of the velocity near the plate. Magnetic force contributes to greater skin friction as the time elapses. Destructive reaction reduces, whereas generative reaction enhances the concentration distribution.

On non-linear magneto convection in a mushy layer with joule heating

This paper studies the flow pattern of non-linear magneto convection that can be realized in a horizontal mushy layer and in the presence of joule heating, which is the amount of heat produced by the induced magnetic field. We consider the appropriate system of equations and the associated boundary conditions for the flow in the mushy layer subjected to a vertical magnetic field of uniform strength. Under certain assumptions and conditions, we determine the stable finite-amplitude solutions of the resulting system using a perturbation approach and stability analysis. We find, in particular, that for a wide range of values of the joule heating parameter and sufficiently small amplitude of the flow, the only stable convective flow is in the form of subcritical down-hexagons with down-flow at the cells' centers and up-flow at the cells' boundaries. This result is in sharp contrast to the case in the absence of joule heating where instead the subcritical up-hexagons with up-flow at the cells' centers and down-flow at the cells' boundaries can be stable. In the presence of joule heating the stable subcritical down-hexagons were found to be enhanced with increasing the strength of the externally imposed magnetic field.

Dufour Effects on Unsteady Hydromagnetic Radiative Fluid Flow past a Vertical Plate through Porous Medium

The objective of the present study is to investigate diffusion-thermo (Dufour effect) and radiation effects on unsteady MHD free convection flow past an impulsively started infinite vertical plate with variable temperature and uniform mass diffusion in the presence of transverse applied magnetic field through porous medium. At time t > 0, the plate is given an impulsive motion with constant velocity in the vertical upward direction against to the gravitational field. At the same time the plate temperature is raised linearly with time t and the level of concentration near the plate is raised to . A magnetic field of uniform strength is applied normal to the direction to the flow. The dimen- sionless governing equations are solved in closed form by Laplace-transform technique. The effect of flow parameters on velocity, temperature, concentration, the rate of heat transfer and the rate of mass transfer are shown through graphs.

MODELING OF HEAT AND MASS TRANSFER IN A ROTATING VERTICAL POROUS CHANNEL WITH HALL CURRENT

In this study we have obtained an exact solution to the problem of heat and mass transfer in a rotating vertical porous channel taking into account the effects of Hall current. A strong magnetic field of uniform strength is applied along the axis of rotation. The entire system rotates about the axis normal to the plates with a uniform angular velocity. The porous channel is subjected to a constant suction/injection velocity as well as uniform free stream velocity. The nonlinear and coupled governing equations are solved by perturbation technique. The analytical expressions for primary and secondary velocity components, temperature and concentration fields, and shear stresses are obtained. The effects of the magnetic field, rotation of the channel, buoyancy force, Hall current, injection-suction parameter, and the temperature oscillation frequency are described during the course of discussion. The results are presented graphically and discussed.

Endoscope effects on MHD peristaltic flow of a power‐law fluid

To understand the influence of an inserted endoscope and magnetohydrodynamic (MHD) power‐law fluid on peristaltic motion, an attempt has been made for flow through tubes. The magnetic field of uniform strength is applied in the transverse direction to the flow. The analysis has been performed under long wavelength at low‐Reynolds number assumption. The velocity fields and axial pressure gradient have been evaluated analytically. Numerical results are also presented and discussed.

Influence of moving magnetic field on three dimensional Couette flow

A three dimensional steady fully developed MHD Couette flow of a viscous incompressible electrically conducting fluid is analysed. The lower stationary porous plate is subjected to a periodic injection velocity and the upper porous plate in uniform motion to a constant suction velocity. A magnetic field of uniform strength applied normal to the planes of the plates is fixed with the moving plate. Neglecting the induced magnetic field, an approximate solution for the flow field is obtained and discussed with the help of graphs.

MHD Three-Dimensional Couette Flow with Transpiration Cooling

An analysis of the Couette flow between two horizontal parallel porous flat plates of an electrically conducting, viscous, incompressible fluid is presented. The stationary plate is subjected to a transverse sinusoidal injection of the fluid and its corresponding removal by constant suction through the other plate in uniform motion. The flow becomes three-dimensional due to such an injection velocity. A magnetic field of uniform strength is also applied normal to the planes of the plates. The effects of the injection/suction velocity and the magnetic field on the flow field, skin friction, and heat transfer are reported.

The Magnetohydrodynamic Kelvin‐Helmholtz Instability. III. The Role of Sheared Magnetic Field in Planar Flows

We have carried out simulations of the nonlinear evolution of the magnetohydrodynamic (MHD) Kelvin-Helmholtz (KH) instability for compressible fluids in 2.5 dimensions, extending our previous work by Frank et al. and Jones et al. In the present work we have simulated flows in the x-y plane in which a "sheared" magnetic field of uniform strength smoothly rotates across a thin velocity shear layer from the z-direction to the x-direction, aligned with the flow field. The sonic Mach number of the velocity transition is unity. Such flows containing a uniform field in the x-direction are linearly stable if the magnetic field strength is great enough that the Alfvénic Mach number MA = U0/cA < 2. That limit does not apply directly to sheared magnetic fields, however, since the z-field component has almost no influence on the linear stability. Thus, if the magnetic shear layer is contained within the velocity shear layer, the KH instability may still grow, even when the field strength is quite large. So, here we consider a wide range of sheared field strengths covering Alfvénic Mach numbers, MA = 142.9 to 2.

Flow of Two-Immiscible Fluids in Porous and Nonporous Channels

This study considers steady, laminar flow of two viscous, incompressible, electrically-conducting and heat-generating or absorbing immiscible fluids in an infinitely-long, impermeable parallel-plate channel filled with a uniform porous medium. A magnetic field of uniform strength is applied normal to the flow direction. The channel walls are assumed to be electrically nonconducting and are maintained at two different temperatures. When present, the porous medium is assumed to act as an electrical insulator and that it is in local thermal equilibrium with the fluid. The transport properties of both fluids are assumed to be constant. This study is expected to be useful in understanding the influence of the presence of slag layers on the flow and heat transfer aspects of coal-fired Magnetohydrodynamic (MHD) generators when the porous medium is absent and the effects of thermal buoyancy and a magnetic field on enhanced oil recovery and filtration systems where the porous medium is present. The problem is formulated by employing the balance laws of mass, linear momentum, and energy for both phases. Continuous conditions for the velocity and temperature as well as the shear stress and heat flux of both phases at the interface are employed. The resulting governing ordinary differential equations are solved numerically subject to the boundary and interface conditions for the velocity and temperature distributions of both fluids in the channel. Analytical solutions for a special case of the problem where the porous medium is absent or only its inertia effect is neglected are obtained. Comparisons with previously reported velocity profiles are performed and excellent agreements are obtained. A parametric study illustrating the influence of the physical parameters involved in the problem is conducted and the results are presented graphically and discussed. [S0098-2202(00)02101-5]

MHD free convection from an infinite vertical plate in a rotating fluid with Hall and ionslip currents

An explicit finite-difference method is employed to study the MHD free convection fluid flow past an impulsive started vertical infinite plate when a strong magnetic field of uniform strength is applied transversely to the direction of flow. The fluid and the plate are in a state of rigid rotation with a uniform angular velocity O about the z+-axis taken normal to the plate. The velocity and temperature profiles are shown on graphs and results are discussed in terms of the Hall parameter βe, the ionslip parameter βi, and the time t.

MHD convective flow in a rotating fluid with Hall and ion-slip currents

Taking Hall and Ion-slip currents into account the steady magnetohydrodynamic convective flow of a partially ionized gas past an infinite vertical porous plate in a rotating frame of reference is investigated theoretically. A strong magnetic field of uniform strength is applied perpendicular to the plate and the fluid is subjected to a normal suction velocity while the heat flux at the plate is constant. An analytic solution of the problem is obtained and the effect of Hall and ion-slip currents, as well as the other parameter entering into the problem, are discussed and shown graphically.

The effects on the flow field of retaining the Joule heating and viscous dissipation term in the energy equation for the hydromagnetic free-convective oscillatory flow past a porous limiting surface, I

With viscous dissipation and Joule heating taking into account the hydromagnetic two-dimensional oscillating free-convection flow, of a viscous, incompressible and electrically conducting fluid, past an infinite vertical porous limiting surface, is studied. For the solution of the problem it is considered that, the free-stream velocity, the plate temperature and the induced magnetic field are oscillating in the time about constant mean values. The flow is subjected to a constant suction velocity, through the porous surface, and a magnetic field of uniform strength is applied transversely to the direction of the flow. Analytical expressions for the flow field are obtained by solving the coupled non-linear system of equations which describe the flow. The influence of the various parameters entering into the problem is also extensively discussed signifying the importance of retaining the Joule heating and viscous dissipation term in the energy equation.

Magnetohydrodynamic free convective flow and mass transfer through a porous medium bounded by an infinite vertical porous plate with constant heat flux

A theoretical analysis of steady free convective and mass transfer flow is presented when a viscous, incompressible, and electrically conducting fluid flows through a porous medium occupying a semi-infinite region of the space bounded by an infinite vertical porous plate. A magnetic field of uniform strength is applied perpendicular to the plate and the fluid is subjected to a normal suction velocity while the heat flux at the plate is constant. An analytic solution of the problem is obtained and the effects of a porous medium, a magnetic parameter, as well as the other parameter entering into the problem, are discussed and shown graphically.

Hydromagnetic thermal convection between non-uniformly heated plates

The effect of the vertical magnetic field of uniform strength on the stability of natural convection in a thin horizontal fluid layer subject to horizontal as well as vertical temperature gradient has been studied on the basis of linear theory. The boundaries are taken to be rigid, perfectly thermally and electrically conducting having prescribed temperatures and the horizontal temperature gradient is assumed to be small. The analysis is restricted to the case when Prandtl number is greater than magnetic Prandtl number which is met by a large margin under most terristrial conditions. It has been found that the preferred mode of disturbance is stationary and will be a transverse roll or a longitudinal roll depending on three parameters namely Prandtl number, Chandrasekhar number and the ratio of Prandtl number to magnetic Prandtl number. The critical Rayleigh numbers for various values of the above three parameters have been reported.