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1

Oscillatory hartmann two-fluid flow and heat transfer in a horizontal channel

Umavathi J. C., Mateen A., Chamkha A. J., Al-Mudhaf A.

International Journal of Applied Mechanics and Engineering

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2006

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Vol. 11, no 1

155-178

EN

An unsteady Hartmann flow of two immiscible fluids through a horizontal channel with time-dependent oscillatory wall transpiration velocity is investigated. One of the fluids is assumed to be electrically conducting while the other fluid and the channel walls are assumed to be electrically insulating. Separate solutions for each fluid are obtained and these solutions are matched at the interface using suitable matching conditions. The partial differential equations governing the flow and heat transfer are transformed to ordinary differential equations and closed-form solutions are obtained in both fluids' regions of the channel for steady and unsteady conditions. The closed-form results are presented graphically for various values of the Hartmann number, frequency parameter, periodic frequency parameter viscosity and conductivity ratios as well as the Prandtl number to show their effect on the flow and heat transfer characteristics.

2

Thermophoresis free convection from a vertical cylinder embedded in a porous medium

Chamkha A. J., Jaradat M., Pop I.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no 3

471-481

EN

This paper deals with the steady free convection over an isothermal vertical circular cylinder embedded in a fluid-saturated porous medium in the presence of the thermophoresis particle deposition effect. The governing partial differential equations are transformed into a set of non-similar equations, which are solved numerically using an implicit finite-difference method. Comparisons with the previously published work are performed and the results are found to be in excellent agreement. Many results are obtained and a representative set of these results is displayed graphically to illustrate the influence of the various physical parameters on the wall thermophoretic deposition velocity and concentration profiles.

3

Free convection from a vertical cylinder embedded in a porous medium filled with cold water

Chamkha A. J., Bercea C., Pop I.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no 2

273-283

EN

A free convection boundary layer flow along a heated vertical cylinder embedded in a porous medium saturated with pure or saline water at low temperatures, up to 20oC, is considered. The boundary layer analysis is formulated in terms of Darcy's law and a new density equation of state, which is of very high accuracy and of simple form, is postulated. Numerical solutions are presented and the flow field characteristics are analysed in detail for both cases of downward and upward flows. A very good agreement between the present results and those reported for particular situations was found.

4

Mixed radiation-convection boundary layer flow of an opically dense fluid along a vertical flat plate in a non-Darcy porous medium

Takhar H. S., Beg O. A., Chamkha A. J., Filip D., Pop I.

International Journal of Applied Mechanics and Engineering

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2003

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Vol. 8, no 3

483-496

EN

The combined effects of thermal radiation flux, thermal conductivity, Reynolds number and non-Darcian (Forcheimmer drag and Brinkman boundary resistance) body forces on steady laminar boundary layer flow along a vertical surface in an idealized geological porous medium are investigated. The classical Rosseland one-dimensional diffusion approximation is implemented in the energy equation to avoid solving the general integro-differential equation for radiative transfer. Pseudo-similarity transformations are invoked and the resulting highly coupled and non-linear set of ordinary differential equations for momentum and energy equations are solved numerically using a well-tested and highly accurate shooting Runge-Kutta quadrature with a Merson-Gill algorithm. It is shown that the dimensionless velocity functions generally increase with rising radiation parameter and the Prandtl number, and the dimensionless temperature functions decrease as the non-Darcian body forces decrease. It is also shown that the dimensionless temperature functions rise in magnitude with rising radiation parameter and the Prandtl number but are depressed by lowered non-Darcian resistance parameter and rising Reynolds number. Generally radiation is seen to substantially boost the overall heat transfer.