Presence Of Variable Magnetic Field Research Articles

Unsteady Hydromagnetic Non-Newtonian Nanofluid Flow Past a Porous Stretching Sheet in the Presence of Variable Magnetic Field and Chemical Reaction

Unsteady Hydromagnetic Non-Newtonian Nanofluid Flow Past a Porous Stretching Sheet in the Presence of Variable Magnetic Field and Chemical Reaction

On the Design of Cylindrical Magnetorheological Clutches

Magnetorheological fluids (MRFs) exhibit variable mechanical properties in response to magnetic stimuli. Thanks to their rapid and reversible viscosity changes, MRFs can be utilized in a variety of applications including torque transmission devices such as clutches. In this work, the geometrical design of cylindrical MR clutches is investigated with the aim of optimizing the torque transmission capability. Effects of design parameters such as radius, gap size, effective length, and MRF volume are investigated in the presence of variable magnetic field. Magneto-mechanical behavior of some MR fluids with different particle content are investigated by means of two different constitutive models to simulate the clutch performance in a range of geometrical parameters. It is shown that the transmitted torque increases nonlinearly by inner radius of the clutch, for example, in the studied range, 150% higher torque is achieved for only 40% larger radius. The clutch’s gap size does not much affect the torque, however, since it significantly affects the required volume of MRF, a lower gap size is favorable. The torque is also calculated for constant volumes of the MRFs. At a certain volume, although a higher radius translates to a shorter length, it is still favorable. For example, a 40% increase in the design radius, almost doubles the transmitted torque for both the studied MRFs. Moreover, a clutch filled by an MRF with higher particle content can transmit higher torques. It is also concluded that increasing the clutch’s radii is an easier way to improve the mean torque while altering the applied magnetic field is a better way to adjust the range of achievable torques. The simulations also demonstrate the importance of an accurate and reliable constitutive model in the design of MR devices. It is shown that Bingham model is not reliable at high magnetic fields as it underestimates the transmitted torque though calibrated at each field intensity. However, the employed nonlinear model provides more reliable results by only being calibrated at an arbitrary field.

Numerical Study of the Effect of Nanofluid on Heat Transfer of a Channel in the Presence of Variable Magnetic Field with Obstacles

Numerical Study of the Effect of Nanofluid on Heat Transfer of a Channel in the Presence of Variable Magnetic Field with Obstacles

Heat transfer and pressure drop in a sinus blowing of copper oxide- water non-Newtonian nanofluid in a sudden expansion process in the presence of variable magnetic field: a numerical solution

ABSTRACT In the current article, the effect of nanofluid blast on the forced convection heat transfer in the intra-channel turbulent flow with a sudden expansion is investigated. The different cases of Newtonian, non-Newtonian, and incompressible fluids have been studied. The effects of non-Newtonian fluid index, magnetic field, nanoparticle volume fraction and nanofluid blowing frequency parameters on the pressure drop and heat transfer in the intra-channel flow have been reviewed. The simulation was performed using finite volume method as the solution strategy. The results revealed that higher values of Re and nanoparticles volume fraction resulted in the Nusselt number increasement. Also, increasing the magnetic field and decreasing the non-Newtonian fluid index increased the forced heat transfer coefficient and subsequently the Nusselt number. The results showed that the sinus velocity caused to increase the rate of the heat transfer and slightly lower friction coefficient. However, higher frequencies caused increasing of heat transfer and friction coefficient. Finally, it was founded that higher values of the Re had the most influence on the performance of the system and the magnetic field and sinus velocity were in the next step.

Influence of Heat and Mass Transfer on Two-Phase Blood Flow with Joule Heating and Variable Viscosity in the Presence of Variable Magnetic Field

In this paper, simultaneous effects of viscous dissipation and Joule heating on unsteady two-phase blood flow through a stenosed artery in the presence of variable applied magnetic field have been investigated. The present two-layered model of blood flow consists of a central core of suspended erythrocytes and a cell-depleted plasma layer surrounding the core. It is assumed that the viscosity of the cell-free plasma layer is constant while the viscosity of the core is a function of the hematocrit level. A consistent system of nonlinear partial differential equations is solved numerically using shooting methods to estimate the flow rate, flow resistance and wall shear stress. The quantitative profile analysis of velocity, temperature and concentration as well as the Nusselt number and Sherwood number is carried out over the entire arterial segment. To validate the model, a comparative study has been done between the present results and the experimental results for the cell velocity distribution of 40% RBC containing blood which exhibits that the present results are in fairly good agreement with the experimental results. The velocity contours have been plotted to understand the flow pattern in the diseased narrowed artery, which alters significantly in the downstream of the stenosis under the influence of magnetic field.

Free Convective 3D Stretched Radiative Flow of Nanofluid in Presence of Variable Magnetic Field and Internal Heating

Free Convective 3D Stretched Radiative Flow of Nanofluid in Presence of Variable Magnetic Field and Internal Heating

Computational model on pulsatile flow of blood through a tapered arterial stenosis with radially variable viscosity and magnetic field

An unsteady two-fluid model of blood flow through a tapered arterial stenosis with variable viscosity in the presence of variable magnetic field has been analysed in the present paper. In this article, blood in the core region is assumed to obey the law of Jeffrey fluid and plasma in the peripheral layer is assumed to be Newtonian. The values for velocity, wall shear stress, flow rate and flow resistance are numerically computed by employing finite-difference method in solving the governing equations. A comparison study between the velocity profiles obtained by the present study and the experimental data represented graphically shows that that the rheology of blood obeys the law of Jeffrey fluid rather than that of Newtonian fluid. The effects of parameters such as taper angle, radially variable viscosity, hematocrit, Jeffrey parameter, magnetic field and plasma layer thickness on physiologically important parameters such as wall shear stress distribution and flow resistance have been investigated. The results in the case of radially variable magnetic field and constant magnetic field are compared to observe the effect of magnetic field in driving the blood flow. It is observed that increase in hematocrit increases the wall shear stress. The values of wall shear stress and flow resistance are obtained at various time instances and compared. It is pertinent to note that the magnitudes of flow resistance are higher in the case of converging tapered than non-tapered and diverging tapered artery.

Nanofluid heat transfer in a permeable enclosure in presence of variable magnetic field by means of CVFEM

This research is about modeling the influence of Lorentz forces on Fe3O4–water nanofluid heat transfer enhancement in a permeable cavity. Shape factor influence on thermal conductivity of nanofluid is taken into consideration. Vorticity stream function formulation is utilized. The solutions of final equations are obtained by Control Volume based Finite Element Method. Graphs are shown for different values of radiation parameter (Rd), Darcy number (Da), nanofluid volume fraction (ϕ), Rayleigh number (Ra) and Hartmann number (Ha). Results indicate that heat transfer rate enhances with augment of Hartmann number. Selecting Platelet shaped nanoparticles leads to greatest heat transfer rate.

The effect of variable magnetic field on heat transfer and flow analysis of unsteady squeezing nanofluid flow between parallel plates using Galerkin method

This paper presents a thermal and flow analysis of an unsteady squeezing nanofluid flow and heat transfer using nanofluid based on Brinkman model in presence of variable magnetic field. Galerkin method is used to solve the non-linear differential equations governing the problem. Squeezing flow between parallel plates is very applicable in the many industries and it means that one or both of the parallel plates have vacillation. The effects of active parameters such as the Hartman number, squeeze number, and heat source parameter are discussed. Results for temperature distribution and velocity profile, Nusselt number, and skin friction coefficient by Galerkin method are presented. As can be seen in results, the values of Nusselt number and skin friction coefficient for CuO is better than Al2O3. Also, according to figures, as nanofluid volume fraction increases, Nusselt number increases and skin friction coefficient decreases, increase in the Hartman number results in an increase in velocity and temperature profiles and an increase in squeeze number can be associated with the decrease in the velocity. <br><br><font color="red"><b> This article has been corrected. Link to the correction <u><a href="http://dx.doi.org/10.2298/TSCI171204246E">10.2298/TSCI171204246E</a><u></b></font>

Ramification of variable thickness on MHD TiO2 and Ag nanofluid flow over a slendering stretching sheet using NDM

The present investigation reveals the effect of variable thickness on the steady two-dimensional boundary layer flows of a TiO2-water and Ag-water nanofluid through a slendering stretching sheet. The whole analysis has been performed in the presence of variable magnetic field and variable surface temperature. Similarity transformation has been introduced to renovate the non-linear partial differential equations into ordinary ones and then they were solved using the innovative technique of Natural decomposition method (NDM). The influence of pertinent parameters on velocity and temperature distribution has been illustrated by means of graphs and tables approach. Our analysis conveys that the temperature of the nanofluid reduces due to enhancing of the variable thickness parameter. The rate of heat transfer is significantly reduced for the Ag-water nanofluid with the positive impact of nanoparticle volume fraction.

Unsteady squeezing nanofluid simulation and investigation of its effect on important heat transfer parameters in presence of magnetic field

This paper presents a thermal and flow analysis of an unsteady squeezing nanofluid flow and heat transfer using nanofluid based on Brinkman model in presence of variable magnetic field. Galerkin Method (GM) is used to solve the nonlinear differential equations governing the problem. Squeezing flow between parallel plates are very applicable in the many industries and it means that one or both of the parallel plates have vacillation. The effects of active parameters such as the Hartman number, squeeze number and heat source parameter are discussed. Results for temperature distribution and velocity profile, Nusselt number and skin friction coefficient by Galerkin Method (GM) are presented. As can be seen in results, the values of Nusselt number and skin friction coefficient for CuO is better than Al2O3’s. Also, according to figures, as nanofluid volume fraction increases, Nusselt number increases and skin friction coefficient decreases, increase in the Hartman number results in an increase in velocity and temperature profiles and an increase in squeeze number can be associated with the decrease in the velocity.

Numerical investigation on two-fluid model (micropolar-Newtonian) for pulsatile flow of blood in a tapered arterial stenosis with radially variable magnetic field and core fluid viscosity

In the present study, an unsteady two-fluid model of blood through a tapered arterial stenosis with variable viscosity in the presence of variable magnetic field has been investigated. In this model, blood in the core region is assumed to be micropolar and plasma in the peripheral layer as Newtonian. Finite difference method is employed in solving the governing equations. The solutions for velocity, flow rate, wall shear stress and flow resistance are computed numerically. A comparison between the velocity profiles obtained by the present study and the experimental data is made and a good agreement between them is found. The model is used to study the effect of parameters such as taper angle, radially variable viscosity, hematocrit, the coupling number, the micropolar parameter, magnetic field and plasma layer thickness on physiologically important parameters such as wall shear stress distribution in the stenotic region and flow resistance. The results in the case of constant magnetic field and variable magnetic field are compared to study the effects of magnetic field on the flow of blood. It is found that the magnitudes of wall shear stress and flow resistance are higher in the case of variable magnetic field. It is important to note that the flow resistance is higher for magneto-micropolar fluid than the micropolar fluid. The wall shear stress decreases with increasing hematocrit parameter whereas flow resistance increases with hematocrit when the applied pressure gradient is held fixed. The model clearly shows the situation of a patient with a tapered arterial stenosis under feverish condition. Due care has been taken to compare the present theoretical results with the existing ones including experimental results and good agreement between them has been observed both qualitatively and quantitatively.

Slip Flow Effects over Hydromagnetic Forced Convective Flow over a Slendering Stretching Sheet

Theobjectiveofthisstudyistodeterminethecharacteristicsofhydromagneticflowoveraslendering stretching sheet in slip flow regime. Steady, two dimensional, nonlinear, hydromagnetic laminar flow of an incompressible, viscous and electrically conducting fluid over a stretching sheet with variable thickness in the presence of variable magnetic field and slip flow regime is considered. Governing equations of the problem are converted into ordinary differential equations utilizing similarity transformations. The resulting non-linear differential equations are solved numerically by utilizing Nachtsheim-swigert shooting iterative scheme for satisfaction of asymptotic boundary conditions along with fourth order Runge-Kutta integration method. Numerical computations are carried out for various values of the physical parameters and their effects over the velocity and temperature are analyzed. Numerical values of dimensionless skin friction coefficient and non-dimensional rate of heat transfer are also obtained.

Mn doping instigated multiferroicity and magneto-dielectric coupling in KNbO3

KNb1−xMnxO3 (0 ≤ x ≤ 0.07) samples were synthesized by a two-step process, ball milling of the precursors and then sintering subsequently. Mn doping at Nb site induces a weak ferromagnetism at room temperature and it has been explained with the help of bound magnetic polaron model. Magnetization values at 15 kOe initially increase followed by a decrease with increase in the Mn concentration. Two phase transitions—orthorhombic to tetragonal and tetragonal to cubic, above room temperature were analyzed from the differential scanning calorimetry and temperature dependent dielectric studies. It elucidates the effect of Mn concentration on phase transition temperatures. All the samples exhibit a peak behaviour in the dielectric constant Vs temperature plot at phase transition temperatures. The samples also exhibit leaky ferroelectric loops at room temperature. PUND measurement reveals the true ferroelectric polarization of the samples. The probable origin of magneto-dielectric effect is discussed based on the dielectric study in the presence of variable magnetic field at a frequency of 1 kHz.

Non-uniform magnetic field effect on nanofluid hydrothermal treatment considering Brownian motion and thermophoresis effects

In this paper, heat and mass transfer of nanofluid in presence of variable magnetic field is investigated. The effects of Brownian motion and thermophoresis are taken into account. Control Volume-based Finite Element Method is applied to solve the governing equations in which both effect of ferrohydrodynamic and magnetohydrodynamic are considered. The effects of Rayleigh number, Hartmann number arising from MHD, buoyancy ratio number and Lewis number on the flow and heat transfer characteristics have been examined. Results are presented in the form of streamline, isotherm, isoconcentration and heatline plots. Results show that Nusselt number has direct relationship with Rayleigh number, buoyancy ratio number and Lewis number while it has reverse relationship with Hartmann number.

Temperature dependent viscosity and thermal conductivity effects on hydromagnetic flow over a slendering stretching sheet

The primary focus of this work is to numerically investigate the influence of temperature dependent viscosity and thermal conductivity on hydromagnetic flow over slendering stretching sheet. In the process held at high temperature like glass blowing, the fluid properties like viscosity and thermal conductivity may gets influenced in such temperature which motivated us to analyze those kind of problem. Considering steady, two dimensional, nonlinear, laminar flow of an incompressible, viscous and electrically conducting fluid over a stretching sheet with variable thickness in the presence of variable magnetic field. Numerical computations are carried out for various values of the physical parameters and the effects over the velocity and temperature are analyzed. Numerical values of dimensionless skin friction coefficient and non-dimensional rate of heat transfer are also obtained and presented in tabulated form. It is noticed that, in additional to the magnetic field there are two more regulators which can manipulate to maintain the optimal heat for the glass blowing process to attain required shapes.

Heat transfer and flow analysis of nanofluid flow between parallel plates in presence of variable magnetic field using HPM

In this study, effect of variable magnetic field on nanofluid flow and heat transfer analysis between two parallel disks is investigated. By using the appropriate transformation for the velocity, temperature and concentration, the basic equations governing the flow, heat and mass transfer were reduced to a set of ordinary differential equations. These equations subjected to the associated boundary conditions were solved analytically using Homotopy perturbation method. The analytical investigation is carried out for different governing parameters namely: squeeze number, suction parameter, Hartmann number, Brownian motion parameter, thermophrotic parameter and Lewis number. Results show that Nusselt number has direct relationship with Brownian motion parameter and thermophrotic parameter but it is a decreasing function of squeeze number, suction parameter, Hartmann number and Lewis number.

Ferrofluid heat transfer treatment in the presence of variable magnetic field

In this paper, the Control Volume-based Finite Element Method (CVFEM) is applied to simulate Fe3O4 -water nanofluid mixed convection heat transfer in a lid-driven semi annulus in the presence of a non-uniform magnetic field. The calculations were performed for different governing parameters, namely, Richardson number, viscosity parameter, nanoparticle volume fraction, magnetic number and Hartmann number. Results show that the Nusselt number has a direct relationship with Richardson number and nanoparticle volume fraction, while it has a reverse relationship with Hartmann number and magnetic number. Also, it can be found that the Nusselt number increases by considering magnetic-field-dependent viscosity.

Thermal radiation effects on hydromagnetic flow over a slendering stretching sheet

The main objective of this work is to analyze how the heat transfer rate of variable thickness stretching sheet gets influenced by the thermal radiation environment in the presence of magnetic field. For which, steady, two-dimensional, nonlinear, hydromagnetic laminar flow of an incompressible, viscous, radiating and electrically conducting fluid over a stretching sheet with variable thickness in the presence of variable magnetic field and thermal radiation are considered. The physical model was solved numerically using Nachtsheim–Swigert shooting iteration technique along with fourth order Runge–Kutta integration method. Numerical solutions are obtained for various values of the physical parameters involved in the problem. The heat transfer rate gets suppressed due to significant effect of magnetic field strength and radiation.

Nanofluid flow and heat transfer between parallel plates considering Brownian motion using DTM

The problem of nanofluid hydrothermal behavior in presence of variable magnetic field is investigated analytically using Differential Transformation Method. The fluid in the enclosure is water containing different types of nanoparticles: Al2O3 and CuO. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In this model effect of Brownian motion on the effective thermal conductivity is considered. The comparison between the results from Differential Transformation Method and previous work are in well agreement which proved the capability of this method for solving such problems. The effect of the squeeze number, nanofluid volume fraction, Hartmann number and heat source parameter on flow and heat transfer is investigated. The results show that skin friction coefficient increases with increase of the squeeze number and Hartmann number but it decreases with increase of nanofluid volume fraction. Nusselt number increases with augment of nanoparticle volume fraction, Hartmann number while it decreases with increase of the squeeze number.