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Sultana M.,Mathematics Discipline | Haque M.M.,Mathematics Discipline | Alam M.M.,Mathematics Discipline | Ferdows M.,Japan Atomic Energy Agency | And 2 more authors.
European Journal of Scientific Research | Year: 2011

A unsteady MHD heat transfer by free convective micropolar fluid flow through an infinite vertical porous medium under the action of strong magnetic field have been studied numerically with induced magnetic field. This investigation is performed for the turbulent boundary layer cooling problem with constant suction velocity. The unconditionally stable implicit finite difference technique is used to solve the non-dimensional momentum, angular momentum, magnetic induction and energy equations. The computed values of fluid velocity, angular velocity, induced magnetic field and temperature distributions as well as the steady-state wall shear stress, wall couple stress, current density and Nusselt number are shown graphically. Finally, the important findings are listed here. © EuroJournals Publishing, Inc. 2011.


Haque M.M.,Mathematics Discipline | Alam M.M.,Mathematics Discipline | Ferdows M.,Japan Atomic Energy Agency | Ferdows M.,University of Dhaka | Postelnicu A.,Transilvania University of Brasov
European Journal of Scientific Research | Year: 2011

Unsteady MHD heat and mass transfer by free convective micropolar fluid flow over an infinite vertical porous medium under the action of transverse magnetic field with thermal diffusion have been studied numerically in the presence of constant heat source. This investigation is performed for both cooling and heating problem with constant suction velocity when the medium is subjected to constant heat and mass fluxes. A finite difference technique with stability and convergence analysis is used to solve the non-dimensional momentum, angular momentum, energy and concentration equations. The computed values of fluid velocity, angular velocity, temperature and concentration distributions, wall shear stress, wall couple stress, Nusselt number and Sherwood number are shown graphically. Finally, a qualitative comparison with previous work is tabulated. © EuroJournals Publishing, Inc. 2011.


Mondal R.N.,Mathematics Discipline | Uddin M.S.,Mathematics Discipline | Yanase S.,Okayama University
International Journal of Fluid Mechanics Research | Year: 2010

A numerical study is presented for the solution structure, stability and transitions of non-isothermal flow through a curved square duct by using a spectral method and covering a wide range of the Dean number, Dn, 0 ≤ Dn ≤ 6000 and the curvature, δ, 0 < δ ≤ 0.5. A temperature difference is applied across the vertical sidewalls for the Grashof number Gr Combining double low line 500, where the outer wall is heated and the inner one cooled. First, steady solutions are obtained by the Newton-Raphson iteration method. As a result, two branches of asymmetric steady solutions are obtained. Linear stability of the steady solutions is then investigated. It is found that only the first branch is linearly stable in a couple of interval of Dn for small δ; for large δ, however, the same branch is linearly stable in a single but wide interval of Dn though the branching pattern of the bifurcation diagram is unchanged. When there is no stable steady solution, time evolution calculations as well as their spectral analysis show that typical transition occurs from steady flow to chaos through various flow instabilities, if Dn is increased. It is also found that the transition to periodic or the chaotic state is delayed if the curvature is increased. © 2010 Begell House, Inc.


Mondal R.N.,Jagannath University | Islam Md.S.,Mathematics Discipline
Procedia Engineering | Year: 2013

In this paper, a comprehensive numerical study is presented for the fully developed two-dimensional flow of viscous incompressible fluid through a curved rectangular duct of aspect ratio 3. Unsteady solutions are obtained by using a spectral method and covering a wide range of Dean number 100 ≤ Dn ≤ 1000 and the Grash of number 100 ≤ Gr ≤ 2000. The outer wall of the duct is heated while the inner wall is cooled. The main concern of this study is to find out the unsteady flow behavior i.e whether the unsteady flow is steady-state, periodic, multi-periodic or chaotic, if the Dean number or the Grash of number is increased. It is found that the unsteady flow is a steady-state solution for Dn = 100 at Gr 100 and Gr 2000 but periodic at Gr = 500, 1000, 1500. If the Dean number is increased, the unsteady flow becomes chaotic for any value of Gr in the range. Contours of secondary flow patterns and temperature profiles are also obtained, and it is found that the unsteady flow consists of a two-, four-, six-and eight-vortex solutions. It is also found that the chaotic flow enhances heat transfer more significantly than the steady-state or periodic solutions, if the Dean number is increased. © 2013 The Authors. Published by Elsevier Ltd.

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