Papers by Keyword: Magnetic Field

Abstract: The two dimensional study of natural convection in vertical cylindrical annular enclosure filled with Cu-water nanofluid under magnetic fields is numerically analyzed. The vertical walls are maintained at different uniform hot and cold temperatures, T_H and T_C, respectively. The top and bottom walls of the enclosure are thermally insulated. The governing equations are solved numerically by using a finite volume method. The coupling between the continuity and momentum equations is effected using the SIMPLER algorithm. Numerical analysis has been carried out for a wide range of Rayleigh number (10³ ≤Ra≤10⁶), Hartmann number (1 ≤Ha≤100) and nanoparticles volume fraction (0 ≤φ≤0.08). The influence of theses physical parameters on the streamlines, isotherms and average Nusselt has been numerically investigated.

Abstract: The objective of the current problem is to explore the impact of wall motion on flow, heat and species concentration of a UCM fluid in a magnetohydrodynamic Darcian channel. The flow is confined between two moving walls. The effects of the wall motion on the physical quantities for expanding and contracting cases are studied through non-dimensional numbers and variables. Numerical solutions for the highly nonlinear differential equations are obtained by reducing the governing PDE to ODE using well-established similarity variables. The variation of skin friction, Nusselt and Sherwood numbers has been investigated with the help of surface plots so that the influence of the squeezing number on the other non-dimensional parameters can be deeply understood. The results suggest that the squeezing channel intensifies the mass transfer and skin friction at the walls and it also increases the velocity, temperature and concentration of the fluid across the channel.

Abstract: The data on the occurrence of martensitic transformation in steel under the action of a magnetic field were obtained by the electric resistivity method. The obtained data indicate the possibility of stress-assisted martensite formation in the temperature range of M_s-M_d (in which superplasticity of austenite is observed). This possibility is due to the magnetic heterogeneity of austenite. Nanosized regions with a ferromagnetic order are present in the paramagnetic matrix. They can perceive the energy of the external magnetic field through the magnetostrictive stresses and change the fields of the elastic forces in the crystal lattice. All this leads to a decrease in the energy of formation of the nucleation center.

Abstract: The main topic of this paper is the development of a mathematical model, based on the Lattice Boltzmann equations (LBE), which is proposed for the simulation of the complex convective flow, held in an electrically conducting melt, driven by the combined action of buoyancy, surface-tension, and electromagnetic forces. The lattice Boltzmann method (LBM) is relatively novel and contrasts with the usual well-known methods to physical modeling in the domain of computational fluid dynamics (CFD). Indeed, the LBM describes the fluid (i.e. lattice fluid) at a microscopic level (molecular) and proposes models for the collision between molecules. The full continuum-level physics (i.e. the macroscopic hydrodynamic fields) is implicitly contained in the LB model. Indeed those macroscopic quantities are defined as moments of the so-called particle distribution functions. In the present work, a two-dimensions (2D) LBE-based model is developed to the simulation of convection melt flow driven by the combination of natural buoyancy, surface tension, and electromagnetic forces. The model is applied to numerical modeling of the problems of buoyancy, surface-tension, and electromagnetic driven convection melt flow in an enclosure. The melt system used has a low Prandtl number, which is appropriate to crystal growth melts.

Abstract: An analysis is carried on an unsteady two-dimensional squeezing radiative flow of an incompressible, viscous, electrically conducting fluid in the presence of time-varying transverse magnetic field and chemical reaction. The crux of the analysis centres round, time-varying magnetic field, squeezing of the channel, chemical reaction of diffusing species and radiative heat transfer. These phenomena affect momentum, thermal energy and solutal transport mechanism significantly. The modified governing equations with complex boundary conditions contribute to intricacy of the solution. The Runge-Kutta sixth order integration scheme with shooting technique has been applied to solve the ordinary differential equations under similarity transformations. The analysis reveals that the numerical method applied in the present analysis is as effective and consistent as that of Homotopy Analysis Method (HAM). Further, it is interesting to note that the squeezing of the channel width acts adversely to the resistive force due to the presence of a magnetic field and hence suggests a controlling device to nullify the effect.

Abstract: It was experimentally established earlier that the increment of the electrode wire melting coefficient at submerged arc welding and surfacing with magnetic fields action (with equal parameters of the welding mode) depends on the chemical composition of the wires. It is suggested that this effect depends on the magnetic properties of the welding materials, i.e. electrode wire and base metal. To measure the magnetic properties of welding materials, a method has been developed in which the magnetic properties of welding materials on samples are investigated. The samples were made in the form of tori, on which the primary and secondary windings were placed. The primary circuit contains an ammeter and a voltmeter, as well as a wattmeter that allows to take into account losses in the sample on hysteresis and Foucault currents, and the secondary circuit contains a voltmeter. Experimental data on the magnetic properties of some welding and surfacing wires, as well as of base metals, are obtained. A simplified method is proposed, in which torus samples are also used, but on which only one winding is placed, over which a direct current is flowed. The value of the increment of the electrode wire melting coefficient at arc welding with the action of magnetic fields increases with increasing their magnetic permeability.

Abstract: The paper is focused on the effect of homogenous and inhomogeneous magnetic fields on crystallization, and some physical and chemical properties of silver azide (morphology, electric resistance, defect structure, reactivity) as well. The authors put forward an efficient procedure for growing crystals with specified sizes, reactivity and minimized impurities.

Abstract: This paper deals with synovial joints which are characterized by their large degree of motion. In synovial joints, magnetic field in addition to electric field is added to disperse the nutrients from the synovial fluid to cartilage by considering both BJ and BJR conditions. The governing equation of the physical model is solved analytically and computations are carried out for the parameters involved in the system under different boundary conditions. The obtained computational results indicate that a drastic improvement can be found for the efficiency of artificial joints with combined effects of electric and magnetic fields on electrohydrodynamic dispersion of biological bearings.

Abstract: An investigation has been performed to analyze the impacts of Soret and Dufour on natural convective and heat absorbing flow of viscoelastic radiative nanofluid driven by a linearly stretched sheet considering inclined magnetic field. By making use of suitable linear transformations, the mathematical equations of problem are changed into the extremely non-linear coupled system of ordinary differential equations. Further, solutions of these differential equations are obtained by implementing GFEM (Galerkin finite element method). The consequence of various controlling pertinent parameters on nanofluid velocity, solutal concentration, temperature and nanofluid concentration are illustrated by means of various graphs while from engineering aspect numerical values of the shear stress, wall temperature gradient, solutal and nanoparticles concentration rate at the stretched sheet are presented in different tables. The numerical results are compared for mono and double diffusive nanofluids which yield that the aligned magnetic field, viscoelasticity, solutal and Brownian diffusivity have significant impacts on the flow field. The reliability of implemented method is authenticated by comparing our results with the previously published results under certain conditions, which signifies the correctness of the implemented method. The present investigation is applicable in several industrial processes such as coolant application, nano-drug delivery, cooling of microchip, heat exchanger technology, biological fluid movement and oceanography etc.Keywords: Magnetic field; Viscoelastic nanofluid; Thermal radiation; Heat absorption

Abstract: In this work, the convective flow of heat generating hydromagnetic fluid through a leaky channel is investigated. Due to channel porosity, the asymmetrical slip conditions are imposed on both walls. The coupled dimensionless partial differential equations are reduced to a system of second-order boundary-value problems based on some flow assumptions and solved by Adomian decomposition method (ADM). Variations in velocity and temperature profiles are presented and discussed in detail. The result of the analysis revealed that increasing Hartmann number decreases the flow velocity while the slip parameters enhance the flow.