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Showing papers on "Hartmann number published in 2015"


Journal ArticleDOI
TL;DR: In this paper, the effects of Brownian motion on the effective viscosity and thermal conductivity of nanofluid were investigated. And the results were presented graphically in terms of streamlines, isotherms and isokinetic energy.

556 citations


Journal ArticleDOI
TL;DR: In this article, force convection heat transfer in a lid driven semi annulus enclosure is studied in presence of non-uniform magnetic field and the calculations were performed for different governing parameters namely, the Reynolds number, nanoparticle volume fraction and Hartmann number.

311 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of the squeeze number, nanofluid volume fraction, Hartmann number and heat source parameter on flow and heat transfer was investigated, and the results showed that skin friction coefficient increases with increase of the Nusselt number and Hartmann numbers but it decreases with an increase in the volume fraction.

311 citations


Journal ArticleDOI
TL;DR: In this paper, the effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo-Kleinstreuer-Li) correlation.
Abstract: In this paper magnetohydrodynamic free convection flow of CuO–water nanofluid in a square enclosure with a rectangular heated body is investigated numerically using Lattice Boltzmann Method (LBM) scheme. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. The influence of pertinent parameters such as Hartmann number, nanoparticle volume fraction and Rayleigh number on the flow, heat transfer and entropy generation have been examined. The results show that the heat transfer rate and Dimensionless entropy generation number increase with increase of the Rayleigh number and nanoparticle volume fraction but it decreases with increase of the Hartmann number.

279 citations


Journal ArticleDOI
TL;DR: In this article, the effect of spatially variable magnetic field on ferrofluid flow and heat transfer is investigated and the combined effects of ferrohydrodynamic and magnetohydrodynamic have been taken into account.
Abstract: Effect of spatially variable magnetic field on ferrofluid flow and heat transfer is investigated. The enclosure is filled with Fe3O4–water nanofluid. Control volume based finite element method (CVFEM) is applied to solve the governing equations. The combined effects of ferrohydrodynamic and magnetohydrodynamic have been taken into account. The influences of Magnetic number, Hartmann number, Rayleigh number and nanoparticle volume fraction on the flow and heat transfer characteristics have been examined. Results show that enhancement in heat transfer decrease with increase of Rayleigh number while for two other active parameters different behavior is observed. Also it can be concluded that Nusselt number is an increasing function of Magnetic number, Rayleigh number and nanoparticle volume fraction while it is a decreasing function of Hartmann number.

240 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated thermal radiation in a semi annulus enclosure with Ferrohydrodynamic and magnetohydrodynamic (MHD) flow and heat transfer and showed that Nusselt number is an increasing function of Rayleigh number, nanoparticle volume fraction, magnetic number while it is a decreasing function of with Hartmann number and radiation parameter.
Abstract: In this paper, ferrofluid flow and heat transfer in a semi annulus enclosure is investigated considering thermal radiation. The enclosure has a wall with constant heat flux boundary condition. Combined effects of Ferrohydrodynamic (FHD) and magnetohydrodynamic (MHD) are considered. It is assumed that the magnetization of the fluid is varying linearly with temperature and magnetic field intensity. Control Volume based Finite Element Method (CVFEM) is applied to solve the governing equations. The calculations were performed for different governing parameters namely; the Radiation parameter, Rayleigh number, nanoparticle volume fraction, Magnetic number arising from FHD and Hartmann number arising from MHD. Results show that Nusselt number is an increasing function of Rayleigh number, nanoparticle volume fraction, magnetic number while it is a decreasing function of with Hartmann number and radiation parameter.

218 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated flow and heat transfer of magnetohydrodynamic (MHD) pseudo-plastic nanofluid in a finite film over unsteady stretching surface with internal heating effects.

207 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of magnetic field on nanofluid flow, heat, and mass transfer between two horizontal coaxial cylinders are studied using a two-phase model, and the effect of viscous dissipation is also taken into account.
Abstract: In this study, the effects of magnetic field on nanofluid flow, heat, and mass transfer between two horizontal coaxial cylinders are studied using a two-phase model. The effect of viscous dissipation is also taken into account. By using the appropriate transformation for the velocity, temperature, and concentration, the basic equations governing the flow, heat, and mass transfer are reduced to a set of ordinary differential equations. These equations subject to the associated boundary conditions are solved numerically using the fourth-order Runge–Kutta method. The effects of Hartmann number, Reynolds number, Schmidt number, Brownian parameter, thermophoresis parameter, Eckert number, and aspect ratio on flow, heat, and mass transfer are examined. Results show that the Nusselt number has a direct relationship with the aspect ratio and Hartmann number but it has a reverse relationship with the Reynolds number, Schmidt number, Brownian parameter, thermophoresis parameter, and Eckert number.

194 citations


Journal ArticleDOI
TL;DR: In this article, the effect of non-uniform magnetic field on nanofluid forced convection heat transfer in a lid driven semi-annulus is studied and the effects of Brownian motion and thermophoresis are taken into account.

189 citations


Journal ArticleDOI
TL;DR: In this article, the effect of magnetic field on heat transfer of Al 2 O 3 -water nanofluid in a two-dimensional horizontal annulus was investigated using the lattice Boltzmann method.

163 citations


Journal ArticleDOI
TL;DR: In this article, 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.
Abstract: 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

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of different shaped obstacles (circular, square and diamond) installed under the influence of a uniform magnetic field and uniform heat generation was numerically investigated.
Abstract: In this study, natural convection in a nano-fluid filled cavity having different shaped obstacles (circular, square and diamond) installed under the influence of a uniform magnetic field and uniform heat generation was numerically investigated. The cavity was heated from below and cooled from the vertical sides while the top wall was assumed to be adiabatic. The temperatures of the side walls vary linearly. The governing equations were solved by using Galerkin weighted residual finite element formulation. The numerical investigation was performed for a range of parameters: external Rayleigh number (104 ≤ RaE ≤ 106), internal Rayleigh number (104 ≤ RaI ≤ 106), Hartmann number (0 ≤ Ha ≤ 50), and solid volume fraction of the nanofluid (0 ≤ ϕ ≤ 0.05). It is observed that the presence of the obstacles deteriorates the heat transfer process and this is more pronounced with higher values of Re E . Averaged heat transfer reduces by 21.35%, 32.85% and 34.64% for the cavity with circular, diamond and squared shaped obstacles compared to cavity without obstacles at RaI = 106. The effect of heat transfer reduction with square and diamond shaped obstacles compared to case without obstacle is less effective with increasing values of Hartmann number. Second law analysis was also performed by using different measures for the normalized total entropy generation.

Journal ArticleDOI
TL;DR: In this article, the effect of an external oriented magnetic field on heat transfer and entropy generation of Cu-water nanofluid flow in an open cavity heated from below was investigated.

Journal ArticleDOI
TL;DR: In this paper, the influence of magnetic field on peristaltic flow of a Casson fluid model is considered, and the model is modelled first time under long wavelength and low Reynold's number approximation.

Journal ArticleDOI
TL;DR: In this article, the closed-form solutions of peristaltic flow of Jeffery fluid under the simultaneous effects of magnetohydrodynamics (MHD) and partial slip conditions in a rectangular duct are studied.

Journal ArticleDOI
TL;DR: In this article, the effects of Brownian motion and thermophoresis have been included in the model of nanofluid and the governing equations are solved via homotopy perturbation method.
Abstract: In this study, two phase simulation of nanofluid flow and heat transfer between parallel plates is investigated. The important effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The governing equations are solved via homotopy perturbation method. According to comparison with previous works, this method has good accuracy to solve this problem. The semi analytical investigation is carried out for different governing parameters namely; the squeeze number, Hartmann number, Schmidt number and Eckert number. The results indicate that absolute skin friction coefficient decreases with increase of Hartmann number and squeeze number. Also it can be found that that Nusselt number is an increasing function of Hartmann number, Eckert number and Schmidt number but it is a decreasing function of squeeze number.

Journal ArticleDOI
TL;DR: In this paper, a 3D numerical simulation of an electrically conducting fluid under the influence of a magnetic field in an inclined cylindrical annulus has been performed, where inner and outer cylinders are maintained at uniform temperatures and other walls are thermally insulated.
Abstract: Three-dimensional (3D) numerical simulation of natural convection of an electrically conducting fluid under the influence of a magnetic field in an inclined cylindrical annulus has been performed. The inner and outer cylinders are maintained at uniform temperatures and other walls are thermally insulated. The governing equations of this fluid system are solved by a finite volume (FV) code based on SIMPLER solution scheme. Detailed numerical results of heat transfer rate, Lorentz force, temperature and electric fields have been presented for a wide range of Hartmann number (0 ≤ Ha ≤ 60) and inclination angle (0 ≤ γ ≤ 90). The results indicate that a magnetic field can control the magnetic convection of an electrically conducting fluid. Depending on the direction and strength of the magnetic field, the suppression of convective motion was observed. For vertical cylindrical annulus, increasing the strength of the magnetic field causes the loss symmetry, and as the consequence, isotherms lose their circular shape. With increasing the Hartmann number the average Nusselt number approaches a constant value. For vertical annulus, the effect of Hartmann number on the average Nusselt number is not prominent compared to the case of horizontal annulus.

Journal ArticleDOI
TL;DR: In this paper, the velocity and volume flow rate of an electrically conducting, incompressible and viscous Jeffrey fluid between two slit microparallel plates with corrugated walls are analyzed by using numerical computation.
Abstract: By employing the perturbation method, the approximate analytical solutions of velocity and volume flow rate are presented for electromagnetohydrodynamic (EMHD) flow of an electrically conducting, incompressible and viscous Jeffrey fluid between two slit microparallel plates with corrugated walls. The corrugations of the two walls are described as periodic sinusoidal waves with small amplitude either in phase or half-period out of phase. The effects of the corrugations on the EMHD flow velocity are analyzed by using numerical computation. The variations of velocity profiles and mean velocity parameter and their dependences on the Reynolds number Re, Hartmann number Ha, dimensionless wave number λ of the wall perturbation, the dimensionless relaxation time λ1ω and retardation time λ2ω are explained graphically.

Journal ArticleDOI
TL;DR: In this article, a 3D numerical simulation and multi-objective optimization of natural convection in a cylindrical annulus mold filled with molten potassium under a magnetic field is carried out.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the natural convection in an open cavity with non uniform thermal boundary condition, where the cavity was filled with a water-Al 2 O 3 nanofluid and subjected to a magnetic field in the presence of heat generation or absorption.

Journal ArticleDOI
TL;DR: In this paper, the influence of the Reynolds number (between 20 and 200), Hartmann number and solid volume fraction of the nanoparticle (between 0 and 0.04) on the fluid flow and heat transfer are numerically investigated for different orientation angles of the magnetic field.

Journal ArticleDOI
TL;DR: In this article, the combined effects of hydrodynamic slip, magnetic field, suction/injection and convective boundary conditions on the global entropy generation in steady flow of an incompressible electrically conducting fluid through a channel with permeable plates are studied.

Journal ArticleDOI
TL;DR: In this paper, the peristaltic flow of Jeffrey fluid in an asymmetric rotating channel is studied and the effect of the Hartmann number, the ratio of relaxation to retardation times, time-mean flow, rotation and the phase angle on the pressure gradient, pressure rise, streamline, axial velocity and shear stress are discussed in detail and shown graphically.

Journal ArticleDOI
TL;DR: In this paper, the effects of magnetic field and heat transfer on the peristaltic flow of an incompressible couple stress fluid through porous medium in an inclined asymmetric channel have been studied under the long wavelength approximation.

Journal ArticleDOI
TL;DR: In this paper, the second law of thermodynamics analysis in a three-dimensional microchannel filled with a nanofluid under a magnetic field is numerically studied and the temperature fields, variation of horizontal velocity, thermal resistance, pressure drop, Hartmann and Reynolds numbers are investigated.
Abstract: In this paper, mixed convection as well as second law of thermodynamics analysis in a three-dimensional microchannel filled with a nanofluid under a magnetic field are numerically studied. The temperature fields, variation of horizontal velocity, thermal resistance, pressure drop, Hartmann and Reynolds numbers are investigated. Moreover, heat, frictional and magnetic entropy generation are surveyed in different volume fractions. Analyzing the results of numerical simulations indicates that with increasing Hartmann number, maximum horizontal velocity along the centre line and the inlet and outlet thermal resistance decrease in the microchannel. On the other hand, by enhancing the strength of the imposing magnetic field, heat entropy generation mitigates, while frictional and magnetic ones increase. However, the increasing of two last is very small compared to heat entropy generation. The ratio of Nuavg/(pressure drop) is greater than 10. Therefore, the thermal gain of this microchannel fairly dominates the loss of pressure reduction.

Journal ArticleDOI
TL;DR: In this article, the Lattice Boltzmann Method is applied in order to simulate the magnetic field effect on nanofluid flow and convective heat transfer in a cubic cavity.
Abstract: In this study, Lattice Boltzmann Method is applied in order to simulate the magnetic field effect on nanofluid flow and convective heat transfer in a cubic cavity. The enclosure is filled with ​Al2O3–water nanofluid. Koo–Kleinstreuer–Li correlation is applied to calculate the effective viscosity and thermal conductivity of nanofluid. The effects of active parameters such as Hartmann number, nanoparticle volume fraction and Rayleigh number on flow and heat transfer have been examined. Results indicate that enhancement in heat transfer has direct relationship with Hartmann number while it has inverse relationship with Rayleigh number. Nusselt number increases with increase of nanoparticle volume fraction and Rayleigh number while it decreases with increase of Hartmann number.

Journal ArticleDOI
15 Mar 2015-Energy
TL;DR: In this paper, the authors investigated the impact of entropy generation on peristaltic flow in a tube and found that the entropy generation number attains high values in the region close to the walls of a tube, while it gains low values near the center of the tube.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the Joules heating effects on stagnation point flow of Newtonian and non-Newtonian fluids over a stretching cylinder by means of GA and found the analytical and numerical solutions for the said mathematical model.
Abstract: Purpose – The purpose of this paper is to study the Joules heating effects on stagnation point flow of Newtonian and non-Newtonian fluids over a stretching cylinder by means of genetic algorithm (GA). The main emphasis is to find the analytical and numerical solutions for the said mathematical model. The work undertaken is a blend of numerical and analytical studies. Effects of active parameters such as: Hartmann number, Prandtl number, Eckert number, Nusselt number, Skin friction and dimensionless fluids parameters on the flow and heat transfer characteristics have been examined by graphs and tables. Compression is also made with the existing benchmark results. Design/methodology/approach – Analytical solutions of non-linear coupled equations are developed by optimal homotopy analysis method (OHAM). A very effective and higher order numerical scheme hybrid GA and Nelder-Mead optimization Algorithms are used for numerical investigations. Findings – An excellent agreement with the existing results in limit...

Journal ArticleDOI
TL;DR: In this article, a two-sided lid-driven enclosure in the presence of a horizontal magnetic field has been analyzed by finite difference Lattice Boltzmann method (FDLBM) for laminar mixed convection of non-Newtonian nanofluids.

Journal ArticleDOI
TL;DR: In this article, a numerical study of entropy generation and MHD mixed convection flow of a nanofluid in a vertical porous channel is made, where both assisting and opposing flows are considered.