Begell House Inc.
International Journal of Fluid Mechanics Research
FMR
2152-5102
35
3
2008
Effects of Radiation on Mass and Heat Transfer of a Fluid Through a Porous Medium Over a Stretching Sheet with Suction and Internal Heat Generation or Absorption
203-218
Walid
Aissa
Mechanical Power Department, Faculty of Energy Engineering, Aswan University, Aswan, Egypt
In this paper, the effects of radiation on mass and heat transfer of a laminar boundary layer flow through a porous medium past a linearly stretching surface with suction and internal heat generation (or absorption) are investigated. The study considers the surface with a prescribed uniform surface temperature or prescribed wall heat flux. The transformed momentum and energy equations are solved numerically using a fourth order Runge-Kutta method. Graphs are presented in terms of velocity and temperature fields for various fluid and flow parameters.
Effect of PEM Fuel Cell Operation on Gas Diffusion Layers and Membrane Stresses
219-234
Maher A.R. Sadiq
Al-Baghdadi
Mechanical & Energy Department, Higher Institute of Mechanical Engineering, Yefren, P.O. Box 65943, Libya
Haroun A. K. Shahad
Al-Janabi
Department of Mechanical Engineering, International Technological University, 115 Dollis Hill Lane, London NW2 6HS, UK
A three-dimensional, multi-phase, non-isothermal computational fluid dynamics model of a proton exchange membrane fuel cell has been developed to investigate the hygro- and thermal stresses in PEM fuel cell, which developed during the cell operation due to the changes of temperature and relative humidity. The behaviour of the gas diffusion layers and membrane during operation of a unit cell has been studied and investigated under real cell operating conditions. The results show that the non-uniform distribution of stresses, caused by the temperature gradient in the cell, induces localized bending stresses, which can contribute to delaminating between the membrane and the gas diffusion layers. These stresses may explain the occurrence of cracks and pinholes in the membrane under steady-state loading during regular cell operation. The results show that the maximum von Mises stress in fuel cell for the low, intermediate and high load conditions were 3.12, 3.16, and 3.23 MPa respectively.
Influence of Radiation and Viscous Dissipation on Three-Dimensional Fluctuating Couette Flow and Heat Transfer with Suction/Injection
235-257
Rama C.
Chaudhary
The University of Rajasthan, Department of Mathematics, Jaipur, India
Preeti
Jain
The University of Rajasthan, Department of Mathematics, Jaipur, India
An analysis of three-dimensional unsteady Couette flow between two horizontal parallel porous plates with radiation effect on temperature distribution is presented here. The lower stationary plate is subjected to transverse sinusoidal suction velocity distribution fluctuating with time and the upper porous plate in uniform motion is subjected to constant injection. Due to the periodic variation of suction velocity, the flow becomes three-dimensional. The heat transfer characteristic has also been discussed on taking viscous dissipation into account. The governing equations are solved by adopting complex variable notations and the expressions for the main flow, cross flow and temperature fields are obtained. The wall shear stress and rate of heat transfer in terms of amplitude and phase are finally discussed, incorporating the effects of main controlling parameters as they appear in the governing equations. The results of this parametric study are shown graphically and physical aspects of the problem are discussed.
A Two-Layered Suspension Flow Induced by Peristaltic Waves
258-272
Amit
Medhavi
Department of Mechanical Engineering, SMS Institute of Technology, Sultanpur Road, Lucknow, India
U. K.
Singh
Department of Mechanical Engineering, Kamla Nehru Institute of Technology, Sultanpur, U. P., India
A two-layered suspension flow, consisting of a central layer of a particle-fluid suspension and a peripheral layer of a Newtonian viscous fluid (same as the suspending medium in the central layer), induced by sinusoidal peristaltic waves has been studies. The expressions for the velocity profiles, the pressure drop and the friction force have been obtained. The pressure drop has been shown to be increasing with the particle concentration in the core region and also with the flow rate. The magnitude of the pressure drop is found to be higher in one-layered (one-fluid) analysis than in two-layered (two-fluid) for a given value of the particle concentration and also for a given value of the flow rate. It is noticed that for small values of the flow rate, the pressure drop decreases rapidly with increasing amplitude ratio. However, this property is different for larger values of the flow rate. The friction force possesses character similar to the pressure drop (an opposite character to the pressure rise) for any given set of parameters.
Interaction Particle − Turbulence in Dispersed Two-Phase Flows Using the Eulerian − Lagrangian Approach
273-286
Mohamed Ali
Mergheni
CORIA UMR 6614 CNRS - Université et INSA de Rouen, France; (LESTE) Ecole Nationale d'Ingenieurs de Monastir; Ecole Superieure des Sciences et Technologie de Hammam Sousse, Sousse, Tunisie
H. Ben
Ticha
(LESTE) Ecole Nationale d'Ingenieurs de Monastir, 5019 Monastir, Tunisie
J. C.
Sautet
CORIA UMR 6614 CNRS - Université et INSA de Rouen, Avenue de l'Université, BP 12, 76801 Saint Etienne du Rouvray, Cedex, France
Sassi Ben
Nasrallah
Laboratoire d'Études des Systèmes Thermiques et Énergétiques, Ecole Nationale d'Ingénieurs
de Monastir, Monastir 5019 Tunisie
In this paper numerical simulations of dispersed particulate two-phase flows, based on the Eulerian − Lagrangian approach, are presented with special emphasis on two-way coupling and turbulence modification. The gas phase was calculated based on the Eulerian approach by solving the Navier − Stokes equations. The disperse phase was treated by the Lagrangian approach. The direct influence of the dispersed phase on the continuous phase is usually taken into account by formulating appropriate source terms for all quantities under consideration. In order to validate the proposed model, the gas-particle flow configuration laden with small particles is considered, namely an axisymmetric particle−laden jet flow and an upward pipe flow Modarress et al. The numerical results show good agreement with the experimental data.
Unsteady Flow in the Volute of a Centrifugal Pump with Large Blade Exit Angle
287-298
Wen-Guang
Li
Department of Fluid Machinery, Lanzhou University of Technology, 730050, Lanzhou, China
The unsteady flows in three sections of the volute with rectangular section were mapped by using LDV at both best efficiency and part-loading points respectively while pumping water. The pump is a single-stage, cantilevered centrifugal pump, its impeller is in a closed configuration and the blade outlet angle is 44°. The results show that the fluid velocity fluctuates periodically with the impeller angular positions with respect to a measurement point where the flow was investigated. As increase in the distance from impeller outlet, the velocity damps rapidly and its periodical fluctuation is suppressed. The magnitude of the fluctuation is about 0.2−0.7 of the averaged velocity and decreases with the increase in the distance. The fluctuation magnitude in the flow angle seems larger than that in velocity by 1 − 2 order. The more the measurement point closes to the tongue of volute, the larger the fluctuation in both velocity and flow angle becomes. The averaged velocity declines with increase in the distance from the impeller outlet. However, the averaged flow angle rises at first, then decreases. The liquid angular moment is not conservational and the flow is not axisymmetrical as well in the volute.