Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
11
3
2008
Study of Liquid Distribution during Capillary Rise in Fabrics Using an Electrical Resistivity Technique: Influence of Structure and Composition
An experimental technique has been developed for studying the liquid organization and distribution during capillary rise in fabrics. To detect the small quantity of water that travels along fabric, we used a new electrical method. This method is based on the measurement of the electrical resistance and led to the determination of time-space water content evolution. The obtained results allowed us to deduce the quantity of liquid in the fabric area, the liquid distribution inside the fabric, and finally, the capillary pressure curve of the fabrics and the flow velocity.
Faten
Fayala
Laboratoire d'Etudes des Systèmes Thermiques et Energétiques; and Département de Génie Textile, Ecole Nationale d'Ingénieurs de Monastir, (E.N.I.M), 5019 Monastir, Tunisie
Mohamed
HAMDAOUI
Laboratoire d'Etudes des SystÃ¨mes Thermiques et EnergÃ©tiques; and DÃ©partement de GÃ©nie Textile, Ecole Nationale d'IngÃ©nieurs de Monastir, (E.N.I.M), 5019 Monastir, Tunisie
Patrick
Perre
Laboratoire de Genie des Procedes et des Materiaux, Ecole Centrale Paris, CentraleSupelec, campus de Chatenay-Malabry Grande Voie des Vignes F-92 295 Chatenay-Malabry Cedex, Paris, France
Sassi Ben
Nasrallah
Laboratoire d'Études des Systèmes Thermiques et Énergétiques, Ecole Nationale d'Ingénieurs
de Monastir, Monastir 5019 Tunisie
231-240
Flow in a Curved Porous Channel with a Rectangular Cross Section
Laminar flow in a curved channel with a rectangular cross section is investigated. The channel is occupied by a fluid-saturated porous medium. The flow is driven by a constant azimuthal pressure gradient. The Brinkman extension of the Darcy law is utilized; the momentum equation takes into account the Darcy and Brinkman drag terms. An analytical solution for the velocity field is obtained using a generalized Fourier series. The velocity profile depends on the geometry of the channel (the inner and outer radii of the channel walls and the aspect ratio of the cross section) and the Darcy number.
Andrey V
Kuznetsov
Department of Mechanical and Aerospace Engineering, North Carolina State University, Campus Box 7910, Raleigh, NC 27695-7910, USA
A. A.
Avramenko
Institute of Engineering Thermophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine
241-246
Numerical Simulation of Mixed Convection in a Channel Irregularly Heated and Partially Filled with a Porous Medium
This article studies the numerical simulation of the heat transfer and the mixed convection of an incompressible fluid filling a horizontal channel where some porous blocks are intermittently inserted in transverse to the channel axis. The porous blocks are subjected to heat flux q, while the fluid compartments are subjected to heat flux q'. The local thermal equilibrium is assumed between the fluid and solid particles. We used the Darcy-Brinkman model for the flow in a porous medium. The control volume approach is used for solving the governing moment and energy equations of the mixed convection. Numerical results of the flow, the temperature fields, and the streamlines are presented and discussed. The effects of some characteristic parameters, the Reynolds number, Re, the Darcy number, Da, and the thermal conductivity ratio, Rk, on the behavior flow are analyzed. We have determined particularly the stability curve and the optimal values of Rayleigh, Reynolds, and Darcy numbers permitting the maximum heat transfer from solid particles to fluid ones with the minimum of pressure drop through the channel.
S.
Jaballah
LETTM Laboratory, Department of Physics, Faculty of Sciences of Monastir, 5019 Monastir, Tunisia
Rachid
Bennacer
L2MGC F-95000, University of Cergy-Pontoise, 95031 Cergy-Pontoise Cedex, Paris, France; ENS-Cachan Dpt GC/LMT/CNRS UMR 8535, 61 Ave. du Président Wilson, 94235 Cachan Cedex, France
Habib
Sammouda
Higher School of Science and Technology of Hammam Sousse- Sousse university- Tunisia
Ali
Belghith
Faculte des Sciences de Tunis, Laboratoire des Transferts de Chaleur et de Masse, Campus Universitaire, 1060 Tunis, Tunisia
247-257
Conjugate Natural Convection in a Porous Enclosure Sandwiched by Finite Walls under Thermal Nonequilibrium Conditions
Conjugate natural convection in a thermal nonequilibrium vertical porous layer sandwiched between two equal thickness walls is studied numerically in this article. The horizontal heating is considered, where the outer surfaces of the vertical walls are isothermal at different temperatures with adiabatic horizontal boundaries. The governing parameters considered are the ratio of the wall thickness to its height (D), the wall to fluid thermal conductivity ratio (Rk), and the Rayleigh number (Ra). Two additional parameters arise if the local thermal nonequilibrium model is considered. They are the porosity-scaled thermal conductivity ratio for the porous media (Kr) and the heat transfer coefficient parameter (H). A parametric study is carried out to show the effect of these parameters on the heat transfer and fluid flow characteristics. The numerical results are presented in terms of average Nusselt number for fluid, solid, and wall in addition to the isotherms and flow patterns with different values of these parameters. The total (effective) average Nusselt number is based on the average heat transfer and the arithmetic mean (effective) thermal conductivity of the porous medium. The variations of the total average Nusselt number with Rayleigh number are presented for different values of other parameters.
Nawaf H.
Saeid
Flow Modeling and Simulation Research Cluster, Universiti Teknologi Brunei, Tungku Link,
Gadong, BE 1410, Brunei Darussalam
259-275
Influence of Hall Current on Rotating Flow of a Burgers' Fluid through a Porous Space
This article looks at the effect of Hall current on the flows of a Burgers' fluid in a rotating frame of reference. To characterize the flows in a porous space, a modified Darcy's law has been used. Analytical solutions valid for all values of the frequency are obtained and discussed through several graphs.
S. B.
Khan
Department of Mathematics, Quaid-i-Azam University, Islamabad, 45320, Pakistan
Masood
Khan
Department of Mathematics, Quaid-i-Azam University, Islamabad 44000, Pakistan
277-287
Nonlinear Buoyant Convection in Mushy Layers during Alloy Solidification
We consider the problem of nonlinear steady buoyant convection in horizontal mushy layers during alloy solidification. We analyze the effects of several parameters on the stationary modes of convection in the form of either hexagons or nonhexagons such as rolls, rectangles, and squares. No assumption is made on the thickness of the mushy layer, and a number of simplifying assumptions made in previous nonlinear analyses are relaxed here to study a richer set of phenomena. Using both analytical and numerical methods, we determine the steady solutions to the weakly nonlinear problem. The results of the analyses and computations indicate, in particular, that depending on the range of values of the parameters, bifurcation to nonhexagonal convection can be either supercritical or subcritical, while bifurcation to hexagon pattern convection, corresponding to the smallest value of the Rayleigh number, is subcritical. For variable permeability, subcritical down-hexagons with down-flow at the cell centers and up-flow at the cell boundaries, which have been observed in related experiments, and supercritical nonhexagons were predicted in a particular range of values of the parameters.
B. S.
Okhuysen
Los Alamos National Laboratory, Los Alamos, NM 87545, USA
Daniel N.
Riahi
School of Mathematical and Statistical Sciences,
One West University Boulevard, University of Texas Rio Grande Valley, Brownsville, Texas 78520 USA
291-303
Vortex Instability of Mixed Convection Boundary Layer Flow Adjacent to a Nonisothermal Horizontal Surface in a Porous Medium with Variable Permeability
A linear stability theory is used to analyze the vortex instability of mixed convection boundary layer flow in a saturated porous medium adjacent to a horizontal surface, where the wall temperature is a power function of the distance from the origin. The permeability of the medium is assumed to vary exponentially with distance from the wall. The entire mixed convection regime is divided into two regions. The first region covers the forced convection-dominated regime, which is characterized by the parameter ξf = Rax/Pex3/2 and the eigenvalue Peclet number. The second region covers the free convection-dominated regime, which is characterized by the parameter ξn = Pex/Rax2/3 and the eigenvalue Rayleigh number. The two solutions provide results that cover the entire mixed-convection regime from pure forced- to pure free-convection limit. Velocity and temperature profiles as well as local Nusselt number for the base flow are presented for the uniform permeability (UP) and variable permeability (VP) cases. The critical Peclet and Rayleigh numbers and the associated wave numbers for both the UP and VP cases are obtained. It is found that the VP effect tends to increase the heat transfer rate and destabilize the flow to the vortex mode of disturbance.
Ahmed M.
Elaiw
Department of Mathematics, Faculty of Science, Al-Azhar University, Assiut 71511, Egypt
Fouad S.
Ibrahim
Department of Mathematics, University College, Umm Al-Qura University, Makkah, Saudi
Arabia; Department of Mathematics, Faculty of Science, Assiut University, Assiut, Egypt
305-321