Unsteady Magnetohydrodynamic Flow Research Articles

Hall Effects on Unsteady Magnetohydrodynamic Flow of a Nanofluid Past an Oscillatory Vertical Rotating Flat Plate Embedded in Porous Media

In the current investigative paper, the impact of Hall current on an unsteady magnetohydrodynamic liberated convection revolving flow of a nanofluid restricted with a uniform absorbent medium over an oscillatory moving vertical smooth plate with convective as well as diffusive frontier conditions has been reviewed. The non-dimensionalized governing differential equations by the appropriate frontier conditions are resolved by the perturbations technique. The impacts of the physical constants on the flow as well as the heat transfer features are displayed graphically and analyzed for Cu as well as Al2O3nanoparticles. For the engineering industry, the skin friction coefficient, local Nusselt number, along with the Sherwood’s number are examined numerically in detail.

Time varying control of magnetohydrodynamic duct flow

Optimal control of the unsteady, laminar, fully developed flow of a viscous, incompressible and electrically conducting fluid is considered under the effect of a time varying magnetic field B0(t) applied in the direction making an angle with the y–axis. Thus, the coefficients of convection terms in the Magnetohydrodynamics (MHD) equations are also time-dependent. The coupled time-dependent MHD equations are solved by using the mixed finite element method (FEM) in space and the implicit Euler scheme in time. FEM solutions are obtained for various values of the Hartmann number, Reynolds number, magnetic Reynolds number and for several types of time dependence of applied magnetic field at transient level and steady-state.In this study, we aim to control the unsteady MHD flow by using the time varying coefficient function f(t) in the applied magnetic field B0(t)=B0f(t) as a control function. In addition, control problem is designed to involve the determination of the optimal parameters of the system (Reynolds number, magnetic Reynolds number and the angle θ) regarded as control variables.In the optimization, a discretize-then-optimize approach with a gradient based algorithm is followed. Cost function is designed to regain the prescribed velocity and induced magnetic field profiles as well as the smooth control function with respect to time. Controls are investigated for the regularization parameters included in the cost function. Optimal solutions are achieved for several states of the flow considering Hartmann number and at the time level where the flow stabilizes.

Fast evaluation for magnetohydrodynamic flow and heat transfer of fractional Oldroyd‐B fluids between parallel plates

AbstractIn this work, we establish a model to describe the unsteady magnetohydrodynamic (MHD) flow of fractional Oldroyd‐B fluid between parallel plates on heat transfer, by introducing the fractional derivative into the constitutive equation. The flow is driven by magnetic, electroosmotic and pressure gradient forcings. In the numerical implementation, the spectral collocation method combined with fast algorithm based on sum‐of‐exponentials (SOE) approximation is performed to solve the model. Effects of several parameters on the velocity profiles, temperature field and Nusselt number are investigated graphically.

Unsteady MHD Mixed Convection Flow of Water over a Sphere with Mass Transfer

This paper examines the unsteady magnetohydrodynamic (MHD) mixed convection flow over a sphere combined with variable fluid properties. An implicit finite difference scheme, together with the quasi-linearization, is used to find non-similar solutions for the governing equations. The vanishing skin friction is prevented or at least delayed by enhancing the mixed convection in both the cases of steady and unsteady fluid flow. Both skin friction and heat transfer coefficients are found to be increasing with an increase in time or MHD parameter.

Entropy Optimization in Nonlinear Mixed Convective Flow of Nanomaterials Through Porous Space

Abstract Our intention in this article is to investigate entropy optimization in nonlinear mixed convective unsteady magnetohydrodynamic flow of nanomaterials in porous space. An exponentially stretched sheet creates the liquid flow. Nanomaterial is considered electrically conducting. The concentration and energy expressions comprise viscous dissipation, Joule heating, thermophoresis and Brownian motion aspects. Arrhenius activation energy is considered. Computation of entropy generation based upon the second law of thermodynamics is made. Nonlinear partial expressions are obtained via suitable dimensionless variables. Resultant expressions are tackled by the OHAM technique. Features of numerous variables on entropy, temperature, velocity and concentration are graphically visualized. Skin friction and the temperature gradient at the surface are also elaborated. Comparative analysis is deliberated in tabulated form to validate the previously published outcomes. Velocity is reduced significantly via the suction parameter. The entropy rate increases for higher values of Brinkman, Biot and Hartmann numbers.

Theoretical investigation of unsteady MHD flow within non-stationary porous plates

Porous-permeable structures with magnetohydrodynamics (MHD) flow have a lot of applications in various disciplines of engineering. Transport of ferro-fluid in magnetic field has attained more focus in recent years. In this work, an analysis is accomplished to investigate the MHD transport of in-compressible viscid ferro-fluid (electrically conductive) amid two movable porous-permeable plates (PPP). Here asymptotic method is then selected to solve the model. In this study, the effects of diverse considerable parameters and constraints like surface permeability, Reynold's factor, and Hartmann's factor are elaborated in details.

Analysis of unsteady magnetohydrodynamic radiative thin liquid film flow, heat and mass transfer over a stretching sheet with variable viscosity and thermal conductivity

The present article is related to the study of magnetohydrodynamic (MHD) heat and mass transfer in a thin liquid film over a permeable unsteady stretching surface in the presence of chemical reaction, applied magnetic field, viscous dissipation, and thermal radiation with variable viscosity and thermal conductivity. Computed results for unsteadiness parameter, temperature ratio parameter, radiation parameter in the presence/absence of the viscous dissipation and Ohmic heating are analyzed and discussed. The computed results reveal that the viscous and Ohmic dissipations reduce the temperature gradient profiles in the thin liquid film. Further, the thermal radiation decreases the cooling rate of the thin liquid film but the reverse effect is seen by increasing the Prandtl number.

Unsteady MHD natural convection flow of Casson fluid incorporating thermal radiative flux and heat injection/suction mechanism under variable wall conditions

Unsteady magnetohydrodynamic flow of Casson fluid over an infinite vertical plate is examined under ramped temperature and velocity conditions at the wall. Thermal radiation flux and heat injection/suction terms are also incorporated in the energy equation. The electrically conducting fluid is flowing through a porous material and these phenomena are governed by partial differential equations. After employing some adequate dimensionless variables, the solutions are evaluated by dint of Laplace transform. In addition, the physical contribution of substantial parameters such as Grashof number, radiation parameter, heat injection/suction parameter, porosity parameter, Prandtl number, and magnetic parameter is appropriately elucidated with the aid of graphical and tabular illustrations. The expressions for skin friction and Nusselt number are also derived to observe wall shear stress and rate of heat transfer. A graphical comparison between solutions corresponding to ramped and constant conditions at the wall is also provided. It is observed that graphs of the solutions computed under constant conditions are always superior with respect to graphs of ramped conditions. The magnetic field decelerates the flow, whereas the radiative flux leads to an upsurge in the flow. Furthermore, the shear stress is a decreasing function of the magnetic parameter.

Comparative study by DTM for unsteady viscous flow between the jet engines combustion unit subjected to inclined magnetic field

Purpose The purpose of this study to analyze the unsteady magneto hydrodynamic incompressible viscous fluid flow along the porous parallel plates in which constant periodic suction/injection takes place at lower and upper plate, respectively. By the proper choice of stream function, they obtained exact solution analytically. Velocity components are obtained from exact solution. Design/methodology/approach Emissions of the pollutants from the aviation sectors are doubled compared to 2000. There are many recent developments that are actively developed to combat the emission by increasing the performance of the Jet engines. The role of the computational fluid dynamics and the numerical approaches are crucial in terms of research and development. Findings Velocity profiles like axial and radial have been drawn for various values of M, D, α and θ. The exact solutions have been solved by differential transformation method. The closed form analytical solutions are obtained for the stream function, axial and radial velocities and flow velocity. Originality/value The effects of Darcy parameter, magnetic parameter, Suction Reynolds number and frequency parameter on lower and upper plates are discussed through graphs.

Unsteady MHD flow of Maxwell fluid with Caputo–Fabrizio non-integer derivative model having slip/non-slip fluid flow and Newtonian heating at the boundary

The purpose of this manuscript is to investigate the unsteady magnetohydrodynamics flow of a Maxwell fluid with conjugate effects of heat and mass transfer under the slip and non-slip conditions at the boundary. Moreover, we apply the Caputo–Fabrizio fractional derivative to model the proposed problem. We consider the fluid in a porous medium over a vertical plate with ramped temperature. We take into consideration the influence of thermal radiation in the energy equations. We solve the governing equations by Laplace transform technique, and we use the Stehfest’s algorithm to find the inverse Laplace transform. Hence, we obtain the semianalytical solutions for temperature, concentration and velocity in case of ramped temperature as well as for both slip and non-slip conditions and general motion of the plate. We demonstrate the numerical results by some figures.

Unsteady MHD Couette viscous fluid flow through silver metallic parallel plates with an inclined magnetic field and angular velocity subjected to constant suction at lower plate

Abstract In this paper, we discussed unsteady magneto hydrodynamic incompressible viscous couette flow along the silver metallic parallel plates in which constant periodic suction takes place at the bottom porous silver metallic shield subjected to the magnetic field with inclination along with the rotation of system. By means of appropriate choice of stream function we obtained exact solution analytically. Axial Velocity component and radial Velocity component are obtained from the analytical solution. Velocity profiles like axial and transverse are examined for different parameters α , K r , M a n d ω t . The effects of Magnetic parameter, Suction Reynolds number and Rotation parameter on the plates are discussed and illustrated graphically.

Unsteady Viscous Dissipative Flow of Salty Water in the Presence of a Magnetic Field in a Semi-Infinite Porous Medium

In this paper, an investigation of unsteady free convective magneto-hydro dynamic (MHD) flow of salty water in the presence of a transverse magnetic field has been carried out. An electrically conducting and incompressible fluid is assumed to flow past a semi-infinite vertical porous plate. A constant magnetic field is applied normally to the vertical plate. The Prandtl numbers for salt water are taken to be 1 at 20˚C. The governing equations of the problem contain non-linear partial differential equations that are transformed into ordinary differential equations. An explicit finite difference scheme has been used to solve the transformed ordinary equations generated from this flow problem. The velocity profiles and temperature distribution of the flow field have been discussed and presented graphically.

Unsteady magnetohydrodynamic flow of a compressible liquid through a stainless steel plate of porous medium

Abstract The unsteady MHD flow of a compressible liquid through a stainless steel plate of porous medium described in terms of a non-linear partial differential equation for a liquid pressure or a linear differential equation for the density if gravitational effects are considered to be negligible. In gravitational flow fields the formulation yields a non-linear equation for both density and pressure. A transformation is given and it shows that in the absence of gravitational effects, the solution of the non-linear boundary value problem in terms of the pressure involves no complexity than the solution of the linear problem in terms of the density. More over this transformation gives in addition the solution to a problem in gravity flow.

Assessment of irreversible losses of non-Newtonian nanofluid flow underlying Hall current, chemical reaction and thermal radiation

PurposeTo amend the efficiency of engineering processes and electronic devices, it is very urgent to assess the irreversibility in the term entropy generation (EG). The efficiency of energy transportation in a system can be improved by minimization of the rate of EG. In this context, the aim of the present study is to estimate irreversible losses of an unsteady magnetohydrodynamic (MHD) flow of a viscous incompressible electrically conducting non-Newtonian molybdenum disulfide-polyethylene glycol Casson nanofluid past a moving vertical plate with slip condition under the influence of Hall current, thermal radiation, internal heat generation/absorption and first-order chemical reaction. Molybdenum disulfide (MoS2) nanoparticles are dispersed in the base fluid polyethylene glycol (PEG) to make Casson nanofluid. Casson fluid model is considered to characterize the rheology of the non-Newtonian fluid, whereas Rosseland approximation is adopted to simulate the thermal radiative heat flux in the energy equation.Design/methodology/approachThe closed-form solutions are obtained for the model equations by using the Laplace transform method (LTM). Graphs and tables are prepared to examine the impact of pertinent flow parameters on the pertinent flow characteristics. The energy efficiency of the system via the Bejan number is studied extensively.FindingsAnalysis reveals that Hall current has diminishing behavior on entropy production of the thermal system. Strengthening of the magnetic field declines the velocity components and prop-ups the rate of EG. Adding nanoparticles into the base fluid reduces the EG, whereas there are an optimum volume fraction of nanoparticles for which the EG is minimized. Further, the rate of decay of EG is prominent in molybdenum disulfide-polyethylene glycol in comparison to PEG.Practical implicationsThe results of this study would benefit the industrial sector in achieving the maximum heat transfer at the cost of minimum irreversibilities with an optimal choice of embedded thermophysical parameters. In view of this agenda, this study would be adjuvant in powder technology, polymer dynamics, metallurgical process, manufacturing dynamics of nano-polymers, petroleum industries, chemical industries, magnetic field control of material processing, synthesis of smart polymers, etc.Originality/valueThe novelty of this study is to encompass the analytical solution by using the LTM. Such an exact solution of non-Newtonian fluid flow is rare in the literature. Limited research articles are available in the field of EG analysis during the flow of non-Newtonian nanoliquid subject to a strong magnetic field.

Unsteady magnetohydrodynamic flow of generalized second grade fluid through porous medium with Hall effects on heat and mass transfer

This work investigates the unsteady magnetohydrodynamic flow of generalized second grade fluid through a porous medium with Hall effects on heat and mass transfer. The second grade fluid with a fractional derivative is used for the constitutive equation. A second-order fractional backward difference formula in the temporal direction and a spectral collocation method in the spatial direction are proposed to solve the model numerically. In the numerical implementation, a fast method is applied to decrease the memory requirement and computational cost. The velocity, temperature, and concentration profiles are discussed through graphs. The effects of various parameters on the velocity profiles, temperature field, and concentration field are shown. Results indicate that as the fractional derivative γ increases and the Hall parameter m decreases, the amplitudes of the velocity components decrease.

HEAT AND MASS TRANSFER ON UNSTEADY MHD FLOW THROUGH AN INFINITE OSCILLATING VERTICAL POROUS SURFACE

Analytical solutions of an unsteady magnetohydrodynamic (MHD) flow with heat and mass transfer characteristics of an incompressible, viscous, electrically conducting, and Boussinesq fluid over a vertical oscillating plate embedded in a Darcian porous medium in the presence of a thermal radiation are presented. The fluid considered here is a gray, absorbing/emitting radiating, but nonscattering medium. At time t > 0, the plate temperature and concentration near the plate are raised linearly with time t. The dimensionless governing coupled unsteady boundary layer partial differential equations are solved by the Laplace transform technique. An increase in permeability parameter (K) is found to increase fluid velocities and shear stress in the regime. Also it was found that when the conduction-radiation parameter (R) increased, the fluid velocity and the temperature profiles decreased. Applications of the study are found in materials processing and solar energy collector systems.

Effect of nonlinear radiation on 3D unsteady MHD stagnancy flow of Fe3O4/graphene–water hybrid nanofluid

ABSTRACT Three-dimensional unsteady magnetohydrodynamic stagnancy flow of hybrid nanoliquid, with nonlinear radiation and uneven heat rise/sag, is studied hypothetically. We considered Fe3O4/graphene nanoparticles embedded in water. The physical problem is modelled mathematically and resolved using Runge–Kutta Fourth order with a shooting procedure. Influences of pertinent parameters on the flow and energy transport are noted numerically and graphically. Moreover, the wall friction and the local Nusselt number are computed and a comparative analysis of nano/hybrid nanofluids is performed with the help of streamlines and isotherms. It is found that the drive and energy transport of nano/hybrid nanofluid is highly influenced by the variation in the particle volume fraction as well as unsteadiness factor. Also, the average temperature of nanofluid in the saddle stagnation region is higher than that of hybrid nanofluid.

Transient magnetohydrodynamic flow and heat transfer of fractional Oldroyd-B fluids in a microchannel with slip boundary condition

The unsteady magnetohydrodynamic flow of viscoelastic fluids through a parallel plate microchannel under the combined influence of magnetic, electro-osmotic, and pressure gradient forcings is investigated. The fractional Oldroyd-B fluid is used for the constitutive equation to simulate the viscoelastic behavior of fluid in the microchannel. Considering the important role of slip boundary condition in microfluidics, the Navier slip model at wall is adopted. The Laplace and Fourier cosine transforms are performed to derive the analytical expression of velocity distribution. Then, by employing the finite difference method, the numerical solution of the velocity distribution is given. In order to verify the validity of our numerical approach, numerical solutions and analytical solutions of the velocity distribution are contrasted with the exact solutions of the Newtonian fluid in previous work, and the agreements are excellent. Furthermore, based on the values of the velocity distribution for the fully developed flow, the energy equation including volumetric Joule heating, electromagnetic couple effect, and energy dissipation is solved to give the temperature distribution in the microchannel by using the finite difference method. Finally, the influence of fractional parameters and pertinent system parameters on the fluid flow and heat transfer performance and the dependence of the dimensionless Nusselt number Nu on the Hartmann number Ha and Brinkman number Br are discussed graphically.

Similarity solution for unsteady magnetohydrodynamic flow between two parallel porous plates with an angular velocity

The objective of this paper is to analyse the unsteady magnetohydrodynamic flow of viscous fluid with an angular velocity between parallel porous plates when the fluid is being withdrawn through both the walls of the channel at the same rate. The problem is reduced to a third-order linear differential equation which depends on a Suction Reynolds number R and Hartmann number with angular velocity M1 for which an exact solution is obtained.

Unsteady MHD oscillatory visco-elastic fluid flow through an inclined channel in presence of chemical reaction with Soret and Dufour effects

The purpose of present paper is to analyze the Soret and Dufour effects on an unsteady magneto hydrodynamic oscillatory flow of radiative, visco-elastic fluid through an inclined channel filled with saturated porous medium with non-uniform wall temperature in presence of first-order chemical reaction. The governing dimensionless momentum equation coupled with the energy and mass diffusion equations are solved analytically. The expressions for velocity, temperature, concentration, skin friction, Nusselt number and Sherwood number are obtained and are analyzed graphically for various values of the dimensionless flow parameters.