Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
35
6
2008
MHD Flow and Heat Transfer Past a Semi-Infinite Vertical Plate Embedded in a Porous Medium of Variable Permeability
493-509
Dulal
Pal
Department of Mathematics, Visva-Bharati University Santiniketan, India
A numerical model is developed to study the effects of variable permeability and magnetic field on mixed convection from a vertical plate embedded in a porous medium incorporating the variation of thermal conductivity. The conservation equations that govern the problem are reduced to a system of nonlinear ordinary differential equations. Because of nonlinearity, the governing equations are solved numerically by employing shooting algorithm with Runge-Kutta-Fehlberg integration scheme. The effects of magnetic field on velocity and temperature distributions are studied in detail by considering uniform permeability (UP) and variable permeability (VP) of the porous medium and the results are depicted graphically. The important finding of the present work is that the magnetic field has considerable effects on the boundary layer velocity and on the rate of heat transfer for both the cases of permeability (i.e., UP and VP) of the porous medium. The present numerical results are in good agreement with those provided by other numerical method on a special case.
Radiative Heat Transfer of a Two-Fluid Flow in a Vertical Porous Stratum
510-543
Jawali C.
Umavathi
Department of Mathematics, Gulbarga University, Kalaburgi-585106, Karnataka, India
Ali J.
Chamkha
Department of Mechanical Engineering, Prince Sultan Endowment for Energy and
Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Kingdom of Saudi
Arabia; RAK Research and Innovation Center, American University of Ras Al Khaimah, United Arab Emirates, 10021
M. H.
Manjula
Department of Mathematics, Gulbarga University, Gulbarga, India
Ali F.
Al-Mudhaf
Manufacturing Engineering Department, The Public Authority for Applied Education and Training, P. O. Box 42325, Shuweikh, 70654 Kuwait
The effect of thermal radiation on mixed convection flow of two immiscible fluids in a vertical porous stratum is considered in the presence of a heat source or sink. The flow model is based on the Darcy-Lapwood-Brinkman equation. The general governing momentum and energy equations for the immiscible fluids are coupled and nonlinear and cannot be solved in closed form. However, approximate analytical solutions are obtained for small values of ε = Pr Ec (the product of the Prandtl and Eckert numbers) using the regular perturbation method, while numerical solutions are found for large values of ε. A representation of the results is presented graphically to illustrate the influence of the physical parameters on the solutions. It is found that both the velocity and temperature fields can be controlled effectively by altering the values of the viscosity ratio, width ratio, and heat generation or absorption coefficient.
Hydromagnetic Combined Convection from a Radiating Vertical Stretching Sheet with Surface Mass Transfer
544-556
S.M.M.
EL-Kabeir
Department of Mathematics, Salman bin Abdulaziz University, College of Science and Humanity Studies, Al-Kharj, 11942, Saudi Arabia; Department of Mathematics, Aswan University, Faculty of Science, 81528, Egypt
M. Modather M.
Abdou
Department of Mathematics, Faculty of Science Aswan, South Valley University, Aswan, Egypt; Department of Mathematics, College of Science and Humanity Studies, Salman Bin AbdulAziz University, Al-Kharj, KSA
Rama Subba Reddy
Gorla
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH, 44115 USA; Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA; Department of Mechanical & Civil Engineering, Purdue University Northwest, Westville, IN 46391, USA
A three-dimensional boundary layer solution is presented to investigate the effects of thermal radiation and a transverse magnetic field on the combined convective flow over a vertical stretching surface with suction and blowing. A parametric study illustrating the influence of the radiation parameter R, surface mass transfer parameter φw, and magnetic parameter Mn on friction factor as well as the Nusselt number is presented. The results of the parametric study are shown in graphical as well as tabular forms. The Rosseland approximation is used to describe the radiative heat flux in the energy equation.
Entropy Minimization in Phase Change Energy Systems
557-569
Rama Subba Reddy
Gorla
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH, 44115 USA; Department of Mechanical Engineering, University of Akron, Akron, Ohio 44325, USA; Department of Mechanical & Civil Engineering, Purdue University Northwest, Westville, IN 46391, USA
Thamilselvan
Nallappan
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH, USA
Larry W.
Byrd
Thermal Structures Branch, Air Vehicles Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, OH 45433, USA
David M.
Pratt
Thermal Structures Branch, Air Vehicles Directorate, Air Force Research Laboratory, Wright Patterson Air Force Base, OH 45433, USA
In phase change transport devices, capillary forces drive the overall circulation of working fluid from an evaporator section to a condenser section. An analysis has been provided for the entropy generated for the combined heat and mass transfer in a circular tube in terms of the gradients of velocity, temperature, and concentration as well as the physical properties of the fluid. The heat and mass transfer rates are assumed to be uniform on the surface of the tube. The optimum geometric configuration that corresponds to the minimization of entropy generated and minimization of fluid flow resistance is identified.
Steady and Unsteady Flow Investigations on the Effect of Different Number of Diffuser Vanes
570-780
Ning
He
SPMP, Shanghai Port Machinary LTD, Shanghai, P.R. China
This paper presents a computational analysis of a high-speed centrifugal compressor stage where emphasis is focused on both the steady and unsteady flow investigations and on the effect of different number of diffuser vanes on the stage operating range. The simulations were carried out for a centrifugal stage with a backswept impeller and several diffusers with 11, 22 and 33 vanes. For the steady simulations, an averaging approach was used at the interface between the impeller and the diffuser. For the unsteady simulations, geometry scaling was used to deal with the problem of unequal pitch. As the number of diffuser vanes was increased, the pressure recovery coefficient in the semi-vaneless space at surge condition was found to reduce. Also, as the number of diffuser vanes was increased, the flow distortion became more pronounced in the vaneless and semi-vaneless space. It is proposed that this more distorted flow is harmful to the pressure recovery in the semi-vaneless space giving stages with more diffuser vanes narrower flow ranges. It was also found that the diffuser area ratio is not the dominant factor influencing the flow range when the number of diffuser vanes changes.
Combined Effect of Short Roughness Strip and Concentrated Wall Suction on Coherent Structure in a Turbulent Boundary Layer
581-593
M. O.
Oyewola
Department of Mechanical Engineering University of Ibadan Ibadan, Nigeria
A. A.
Adesina
School of Chemical Engineering and Industrial Chemistry, University of New South Wales,
Hot-wire measurements have been undertaken in a turbulent boundary layer in order to examine the combined effect of short roughness strip and localized wall suction on near-wall coherent structures. The short roughness strip is placed immediately after the suction strip and the suction is applied through a short porous strip for a range of suction rates. The results of Reynolds stresses indicate that the pseudo-equilibrium of the organized motion of the layer have been altered due to the suppression of the near-wall coherent structures. This is evident in the attenuation of the spectra and co-spectra relative to the undisturbed layer. Although, short roughness strip altered the magnitude and wavelength of the effect of suction on the layer, the results suggest that the short roughness strip and suction act independently on the mechanism of the layer.