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1 – 10 of 688Sebastian Prinz, Jörg Schumacher and Thomas Boeck
This paper aims to address the performance of different subgrid-scale models (SGS) for hydro- (HD) and magnetohydrodynamic (MHD) channel flows within a collocated finite-volume…
Abstract
Purpose
This paper aims to address the performance of different subgrid-scale models (SGS) for hydro- (HD) and magnetohydrodynamic (MHD) channel flows within a collocated finite-volume scheme.
Design/methodology/approach
First, the SGS energy transfer is analyzed by a priori tests using fully resolved DNS data. Here, the focus lies on the influence of the magnetic field on the SGS energy transport. Second, the authors performed a series of 18 a posteriori model tests, using different grid resolutions and SGS models for HD and MHD channel flows.
Findings
From the a priori analysis, the authors observe a quantitative reduction of the SGS energy transport because of the action of the magnetic field depending on its orientation. The a posteriori model tests show a clear improvement because of the use of mixed-models within the numerical scheme.
Originality/value
This study demonstrates the necessity of improved SGS modeling strategies for magnetohydrodynamic channel flows within a collocated finite-volume scheme.
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Santosh Chaudhary and Mohan Kumar Choudhary
The purpose of this paper is to investigate two-dimensional viscous incompressible magnetohydrodynamic boundary layer flow and heat transfer of an electrically conducting fluid…
Abstract
Purpose
The purpose of this paper is to investigate two-dimensional viscous incompressible magnetohydrodynamic boundary layer flow and heat transfer of an electrically conducting fluid over a continuous moving flat surface considering the viscous dissipation and Joule heating.
Design/methodology/approach
Suitable similarity variables are introduced to reduce the governing nonlinear boundary layer partial differential equations to ordinary differential equations. A numerical solution of the resulting two-point boundary value problem is carried out by using the finite element method with the help of Gauss elimination technique.
Findings
A comparison of obtained results is made with the previous work under the limiting cases. Behavior of flow and thermal fields against various governing parameters like mass transfer parameter, moving flat surface parameter, magnetic parameter, Prandtl number and Eckert number are analyzed and demonstrated graphically. Moreover, shear stress and heat flux at the moving surface for various values of the physical parameters are presented numerically in tabular form and discussed in detail.
Originality/value
The work is relatively original, as very little work has been reported on magnetohydrodynamic flow and heat transfer over a continuous moving flat surface. Viscous dissipation and Joule heating are neglected in most of the previous studies. The numerical method applied to solve governing equations is finite element method which is new and efficient.
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Fabio Andrade Pontes, Emanuel Negrão Macêdo, Clauderino da Silva Batista, João Alves de Lima and João Nazareno Nonato Quaresma
The purpose of this study is to show the procedure, application and main features of the hybrid numerical-analytical approach known as generalized integral transform technique by…
Abstract
Purpose
The purpose of this study is to show the procedure, application and main features of the hybrid numerical-analytical approach known as generalized integral transform technique by using it to study magnetohydrodynamic flow of electrically conductive Newtonian fluids inside flat parallel-plate channels subjected to a uniform and constant external magnetic field.
Design/methodology/approach
The mathematical formulation of the analyzed problem is given in terms of a streamfunction, obtained from the Navier–Stokes and energy equations, by considering steady state laminar and incompressible flow and constant physical properties.
Findings
Convergence analyses are performed and presented to illustrate the consistency of the integral transformation technique. The results for the velocity and temperature fields are generated and compared with those in the literature as a function of the main governing parameters.
Originality/value
A detailed analysis of the parametric sensibility of the main dimensionless parameters, such as the Reynolds number, Hartmann number, Eckert number, Prandtl number and electrical parameter, for some typical situations is performed.
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Tasawar Hayat, Zeenat Bashir, Sumaira Qayyum and Ahmed Alsaedi
This paper aims to explore the study of magnetohydrodynamic viscous fluid flow past on a stretching cylinder with nonlinear thermal radiation having gyrotactic microorganisms.
Abstract
Purpose
This paper aims to explore the study of magnetohydrodynamic viscous fluid flow past on a stretching cylinder with nonlinear thermal radiation having gyrotactic microorganisms.
Design/methodology/approach
Appropriate transformations reduce the nonlinear partial differential equation to ordinary ones. Subsequent nonlinear equations are calculated to get convergent series solutions.
Findings
Fluid velocity declines for elevating values of magnetic field parameter. For larger values of curvature parameter near the cylinder temperature reduces.
Originality/value
To the best of the authors’ knowledge, magnetohydrodynamic boundary layer flow of viscous fluid by nonlinear stretching cylinder with nonlinear thermal radiation having gyrotatic microorganisms is not studied yet. The purpose is to study this.
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The investigation of fluid flow over a rotating disk has been increasing due to the spread of machine technology. Because of this development, we scrutinized the…
Abstract
Purpose
The investigation of fluid flow over a rotating disk has been increasing due to the spread of machine technology. Because of this development, we scrutinized the Magnetohydrodynamic (MHD) flow of hybrid nanofluid caused by a decelerating rotating disk with Ohmic heating, Soret and Dufour effects. The disk's angular velocity is taken to be an inversely time-dependent linear function. Moreover, the temperature-dependent viscosity of hybrid nanofluid is incorporated in the present investigation. Methanol is considered as base fluid, while copper oxide (CuO) and magnesium oxide (MgO) are nanoparticles.
Design/methodology/approach
Estimated fundamental partial differential equations of flow problems are altered as a dimensionless system of ordinary differential equations using appropriate similarity transformation and solved using a numerical technique: BVP Midrich scheme in Maple software. The impression of emerging non-dimensional parameters is portrayed graphically. All outcomes are shown in the velocity, temperature and concentration profiles.
Findings
The developed flow problem involves a non-dimensional parameter (A) that reveals the deceleration of the disk. For larger values of A, the disk decelerates faster and for some fixed time, the fluid surrounding the disk revolves more rapidly than the disk itself. The radial velocity of fluid diminishes and axial velocity becomes uniform when the disk is subjected to wall suction velocity (B).
Originality/value
This analysis is significant in biomedical engineering, cancer therapeutic, manufacturing industries and nano-drug suspension in pharmaceuticals. The novelty of the current study is the hybrid nanofluid flow with Ohmic heating, Soret and Dufour effects on a decelerating rotating disk. To the best of the author's knowledge, no such consideration has been published in the literature.
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Recent interest in high temperature lubrication, in particular liquid metal lubrication, has prompted an investigation of the possible use of hydromagnetic effects to increase…
Abstract
Recent interest in high temperature lubrication, in particular liquid metal lubrication, has prompted an investigation of the possible use of hydromagnetic effects to increase bearing pressurisation and load capacity. It has been found that by applying an external magnetic field along with an external current source a significant increase in pressurisation can be achieved over the hydrodynamical bearing. With the application of a magnetic field alone, that is under open circuit conditions, no appreciable pressurisation can be achieved except for extremely large magnetic fields. Several bearing geometries are analysed, the journal bearing, thrust bearing, and slider bearing, all with the same general conclusions. Various possible magnetic field and electrode configurations are discussed.
Yuan Ping, Haiyan Su and Xinlong Feng
The purpose of this paper is to propose a local parallel finite element algorithm based on fully overlapping domain decomposition technique to solve the incompressible…
Abstract
Purpose
The purpose of this paper is to propose a local parallel finite element algorithm based on fully overlapping domain decomposition technique to solve the incompressible magnetohydrodynamic equations.
Design/methodology/approach
The algorithm uses a lower-order element pair to compute an initial approximation by the Oseen-type iteration and uses a higher-order element pair to solve a linear system in each processor.
Findings
Besides, the convergence analysis of local parallel finite element algorithm is given. Finally, numerical experiments are presented to verify the efficiency of the proposed algorithm.
Originality/value
Compared with the numerical solution of the common two-step method, this method is easy to realize and can produce a more accurate solution. And, this approach is executed in parallel, so it saves a lot of computational time.
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Sahin Ahmed, Abdul Batin and Ali J. Chamkha
The purpose of this paper is to examine the effects of Darcian drag force and radiation-conduction on unsteady two-dimensional magnetohydrodynamic flow of viscous, electrically…
Abstract
Purpose
The purpose of this paper is to examine the effects of Darcian drag force and radiation-conduction on unsteady two-dimensional magnetohydrodynamic flow of viscous, electrically conducting and Newtonian fluid over a vertical plate adjacent to a Darcian regime in presence of thermal radiation and transversal magnetic field. A well-tested, numerically stable Crank-Nicolson finite-difference procedure is employed for the conservation equations. Excellent agreement is obtained for numerical solutions with previously published work.
Design/methodology/approach
In this investigation, an efficient, accurate, extensively validated and unconditionally stable finite-difference scheme based on the Crank-Nicolson model is developed to solve the governing coupled, non-linear partial differential equations. The accuracy and effectiveness of the method are demonstrated.
Findings
Different numerical results are obtained and presented graphically to explain the effect of various physical parameters on the velocity and temperature profiles, local, as well as average, skin friction and Nusselt number. It is found that, with a rise in Darcian drag force, flow velocity and temperature are reduced, but increased for all times. Both average and local skin frictions are reduced considerably with an increase in Darcian drag force, but reversed behavior is observed for the local Nusselt number. Increasing the thermal radiation effects accelerated the flow velocity as well as the fluid temperature and wall local skin friction in a saturated porous medium, but effectively reduced the local Nusselt number and average Nusselt number at the wall. Comparison with previously published works in the limits shows excellent agreement.
Research limitations/implications
The analysis is valid for unsteady, two-dimensional laminar flow of an optically thick no-gray gas, electrically conducting, and Newtonian fluid past an isothermal vertical surface adjacent to the Darcian regime with variable surface temperature. An extension to three-dimensional flow case is left for future work.
Practical implications
Practical interest of such study includes applications in electromagnetic lubrication, boundary cooling, bio-physical systems and in many branches of engineering and science. It is well known that the effect of thermal radiation is important in space technology and high temperature processes. Thermal radiation also plays an important role in controlling heat transfer process in polymer processing industry.
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The purpose of this article is to analyze the magnetohydrodynamic viscous liquid flow with heat absorption/generation. Flow is induced by an unsteady stretching curved surface. A…
Abstract
Purpose
The purpose of this article is to analyze the magnetohydrodynamic viscous liquid flow with heat absorption/generation. Flow is induced by an unsteady stretching curved surface. A time-dependent magnetic field is utilized.
Design/methodology/approach
The resulting nonlinear system is solved through shooting method.
Findings
An increment in the values of curvature A and unsteadiness parameters correspond to higher velocity, temperature and concentration fields. There is a reduction in the temperature and related layer via Prandtl number. Skin friction is increasing factor of magnetic number. Local Nusselt and Sherwood numbers are lower for greater magnetic number.
Originality/value
To the best of author's knowledge, no such consideration has been given in the literature yet.
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Sundarammal Kesavan, Ali J. Chamkha and Santhana Krishnan Narayanan
– The purpose of this paper is to consider magnetohydrodynamic (MHD) squeeze film characteristics between finite porous parallel rectangular plates with surface roughness.
Abstract
Purpose
The purpose of this paper is to consider magnetohydrodynamic (MHD) squeeze film characteristics between finite porous parallel rectangular plates with surface roughness.
Design/methodology/approach
Based upon the MHD theory, this paper analyzes the surface roughness effect squeeze film characteristics between finite porous parallel rectangular plates lubricated with an electrically conducting fluid in the presence of a transverse magnetic field.
Findings
It is found that the magnetic field effects characterized by the Hartmann number produce an increased value of the load carrying capacity and the response time as compared to the classical Newtonian lubricant case. The modified averaged stochastic Reynolds equation governing the squeeze film pressure is derived.
Research limitations/implications
The present study has considered both Newtonian fluids and non-Newtonian liquids.
Practical implications
The work represents a very useful source of information for researchers on the subject of MHD squeeze film with finite porous parallel rectangular plates lubricated with an electrically conducting fluid.
Originality/value
This paper is relatively original and illustrates the squeeze film characteristics between finite porous parallel rectangular plates with MHD effects.
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