Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
13
1
2010
ANISOTROPIC DIFFUSION IN FIBROUS POROUS MEDIA
Some porous media possess fibrous structures. Examples include the geologically deformed porous rocks, white matter in human brain tissue, and fiber-reinforced composite materials. These anisotropic porous media show strong diffusive anisotropy. This study focused on a system consisting of randomly placed parallel rods as a model of fibrous porous media, and describes the analysis of three-dimensional diffusive anisotropy through the lattice random walk computer simulations. The rods were completely impermeable, and nonsorbing random walkers migrate in the percolated pore space between the parallel rods. Direction-dependent self-diffusivity was calculated by taking the time derivative of the mean square displacement of the walkers, and its three-dimensional shape was expressed graphically as a shell-like object by polar representation. Systematic simulations for varied rod packing densities revealed that the shell-like object was no longer convex ellipsoidal, but was constricted in the direction normal to the rod axis when the maximum-to-minimum diffusivity ratio of the diffusion ellipsoids exceeded 1.5 (i.e., when the rod volume fraction exceeded 34 vol %). An analytical solution of the direction-dependent self-diffusivity with constriction is presented for the lattice walk along a straight pore. The solution suggests that the ellipsoid constriction observed for the randomly placed parallel rods is a remnant of the anisotropic pore structure of the hexagonal closest packing, which is the end member of the rod packing. The onset condition of the constriction of the shape of the direction-dependent self-diffusivity is investigated analytically using a diffusion tensor expression. The analysis reveals that the constriction occurs when the maximum-to-minimum diffusivity ratio exceeds exactly 1.5, which agrees well with the simulation results. The critical value of 1.5 can also be applicable to the geologically deformed natural porous rocks having more complex pore structure compared with the simple rod packing system.
Yoshito
Nakashima
National Institute of Advanced Industrial Science and Technology (AIST), Central 7, Higashi 1-1-1, Tsukuba, Ibaraki 305-8567, Japan
Susumu
Kamiya
National Institute of Advanced Industrial Science and Technology (AIST), Central 7, Higashi 1-1-1, Tsukuba, Ibaraki 305-8567, Japan
1-11
IMPACT OF PULL SPEED ON WETOUT FOR A DETACHED INJECTION CHAMBER IN RESIN INJECTION PULTRUSION
This work investigates the use of a tapered injection chamber "detached" from the pultrusion die in order to reduce the maximum resin pressures occurring inside the injection chamber; thus making the process more economical and efficient. This work also seeks to achieve complete fiber reinforcement wetout and thus produce quality pultruded parts in the resin-injection pultrusion process. Complete wetout of the dry fiber reinforcement by the liquid resin depends strongly on pull speed. Typically, higher pull speeds yield higher resin pressures inside the tapered section of the injection chamber; higher liquid resin pressures are undesirable from safety and design considerations. A 3D finite volume technique was developed to simulate the flow of polyester resin through glass rovings. Results illustrate the impact of the tapering of the injection chamber walls on the minimum injection pressure necessary to achieve complete fiber matrix wetout and the maximum resin pressure occurring inside the injection chamber. Important injection chamber design information is also presented.
Jeffrey A.
Roux
University of Mississippi, Department of Mechanical Engineering, USA
Anil L.
Jeswani
University of Mississippi, Department of Mechanical Engineering, USA
13-27
OSCILLATORY ROTATING FLOWS OF A FRACTIONAL JEFFREY FLUID FILLING A POROUS SPACE
Exact analytic solutions have been developed for three oscillatory flow problems in a rotating system. Constitutive equations of a Jeffrey fluid are considered. An incompressible and electrically conducting fluid occupies a porous space. The Hall and slip effects are analyzed. Fractional calculus and Fourier transform approaches are utilized in the present analysis. Graphs are plotted, and physical interpretation is made for the several cases of interest.
Masood
Khan
QAU
Kamran
Fakhar
Department of Mathematics, Faculty of Science, University Technology Malaysia; Ibnu Sina Institute for Fundamental Science Studies, (UTM)
Norsarahaida Saidina
Amin
Department of Mathematics, Faculty of Science, University Technology Malaysia, 81300 Skudai, Johor, Malaysia
29-38
HYDROGEN ADSORPTION IN ORDERED MESOPOROUS CARBON SYNTHESIZED BY A SOFT-TEMPLATE APPROACH
An ordered mesoporous carbon was synthesized with soft-template approach as a potential adsorbent for hydrogen storage through physical adsorption. The carbon adsorbent prepared in this work has a Brunauer-Emmett-Teller (BET) specific surface area of 798 m2/g, uniform pore size distribution with an average pore diameter of 6.26 nm, and pore volume of 0.87 cm3/g. Hydrogen adsorption equilibrium and kinetics in the carbon adsorbent were measured in a volumetric adsorption apparatus at 77,194.5, and 298 K. A hydrogen adsorption capacity of 1.27 wt % was observed at 1.05 bar and 77 K, hydrogen diffusivity in the carbon is estimated to be 1 × 10−6 cm2/s at 194.5 K, and activation energy for hydrogen diffusion in the carbon is 0.236 kJ/mol. The isosteric heat of adsorption for hydrogen in the carbon adsorbent is between 3 and 6 kJ/mol, which is in the same range of the heat of adsorption of hydrogen measured on other carbonaceous materials.
Dipendu
Saha
Department of Chemical Engineering, New Mexico State University, P.O. Box 30001, MSC 3805, Las Cruces, New Mexico 88003, U.S.A.
Zuojun
Wei
Zhejiang University, College of Material Science and Chemical Engineering, Hangzhou, China
Sri H.
Valluri
Department of Chemical Engineering, New Mexico State University, P.O. Box 30001, MSC 3805, Las Cruces, New Mexico 88003, U.S.A.
Shuguang
Deng
Department of Chemical Engineering, New Mexico State University, P.O. Box 30001, MSC 3805, Las Cruces, New Mexico 88003, U.S.A.
39-50
EFFECTS OF VARIABLE VISCOSITY AND THERMAL CONDUCTIVITY ON THE BRINKMAN MODEL FOR MIXED CONVECTION FLOW PAST A HORIZONTAL CIRCULAR CYLINDER IN A POROUS MEDIUM
This work presents a performance analysis of mixed convection boundary layer flow past a horizontal circular cylinder embedded in a fluid-saturated porous medium in a vertical stream flow using the Darcy-Brinkman model. The surface temperature is assumed to be constant. The fluid viscosity and thermal conductivity are assumed to vary as a linear function of temperature. Both cases of a heated (assisting flow) and a cooled (opposing flow) cylinder are considered. The governing equations reduce to the similar Darcy's model, while it becomes nonsimilar for the Darcy-Brinkman model, and they are solved numerically employing the finite difference method. The effects of the Darcy-Brinkman parameter Γ, mixed convection parameter λ, viscosity parameter r, and thermal conductivity parameter ε are studied. It is found that cooling the cylinder (λ < 0) brings the boundary layer separation point nearer to the lower stagnation point, and for sufficiently large negative values of the mixed convection parameter (in absolute sense) there is no boundary layer on the cylinder in the case of variable and constant fluid properties. Heating the cylinder (λ > 0) delays the separation of the boundary layer and can suppress it completely for large values (λ > 0). Results for the details of the velocity and temperature fields as well as skin friction and rate of heat transfer at the wall are presented. Results are compared with previously published work and are found to be in excellent agreement.
Z. Z.
Rashed
Department of Mathematics, Faculty of Girls, Arar, Saudi Arabia
I. A.
Hassanien
Department of Mathematics, Faculty of Science, Assiut University, Assiut, Egypt
53-66
STEADY FLOW OF A FOURTH GRADE FLUID IN A POROUS MEDIUM
In this paper, the flow of a fourth grade fluid past a porous plate is studied. The flow equations are modelled based on modified Darcy's law. An analytic solution of the highly nonlinear problem is obtained by the homotopy analysis method (HAM). The convergence of the series solution is checked. The variation of velocity profiles in the presence of porous medium effects is discussed through graphs. It is noted that such series solution is only possible in the case of suction.
Muhammad
Sajid
Department of Mathematics and Statistics, International Islamic University, Islamabad 44000, Pakistan
Saima
Noreen
COMSATS Institute of Information Technology, Islamabad-Pakistan
67-74
HEAT AND MASS TRANSFER IN TRANSIENT FLOW BY MIXED CONVECTION BOUNDARY LAYER OVER A STRETCHING SHEET EMBEDDED IN A POROUS MEDIUM WITH CHEMICALLY REACTIVE SPECIES
An analysis is carried out to study the coupled heat and mass transfer in transient flow by a mixed convection boundary layer past an impermeable vertical stretching sheet embedded in a fluid-saturated porous medium in the presence of a chemical reaction effect. The stretching velocity, the surface temperature, and concentration are assumed to vary linearly with the distance along the surface. The flow is impulsively set into motion rest, and both the temperature and concentration at the surface are also suddenly changed from that of the ambient fluid. The governing partial differential equations are transformed into the self-similar unsteady boundary layer equations and solved by the Runge-Kutta integration scheme with shooting method for the whole transient from initial state (ξ = 0) to final steady state flow (ξ = ∞). Numerical results for the velocity, temperature, and concentration profiles as well as the variation of the local skin friction coefficient, local Nusselt and Sherwood numbers with the Darcy number, buoyancy, and chemical reaction parameters are presented graphically and discussed. This is done to elucidate the influence of the various parameters involved in the problem on the solution.
A.M.
Rashad
Department of Mathematics, Aswan University, Faculty of Science, Aswan, 81528, Egypt
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
75-85
CHEMICAL REACTION AND MAGNETOHYDRODYNAMIC EFFECTS ON FREE CONVECTION FLOW PAST AN INCLINED SURFACE IN A POROUS MEDIUM
A boundary layer analysis has been presented for the free convection flow past an inclined surface in a Newtonian fluid-saturated porous medium. The effects of chemical reaction, magnetohydrodynamics, radiation, viscous dissipation, and heat generation are included. Rosseland approximation is used to describe the radiative heat flux in the energy equation. Four different cases of flow have been studied, namely, an isothermal surface, a uniform surface heat flux, a plane plume, and flow generated from a horizontal line energy source on a vertical adiabatic surface. Numerical results are presented by using the perturbation analysis. The obtained results are compared, and a representative set is displayed graphically to illustrate the influences of the flow parameters on the velocity, temperature, and concentration. Numerical values for the skin-friction coefficient, Nusselt number, and Sherwood number are presented in a tabular form with parameters characterizing the radiation, viscous dissipation, permeability of porous medium, heat generation, and chemical reaction.
M. A.
Mansour
Department of Mathematics, Assuit University, Faculty of Science, Assuit, Egypt
N. F.
El-Anssary
Department of Mathematics, Faculty of Science, South Valley University, Qena, Egypt
Abdelraheem M.
Aly
Department of Mathematics, Faculty of Science, South Valley University, Qena, Egypt; Department of Mathematics, Faculty of Science for Girls, Abha, King Khalid University, Saudi
Arabia
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
87-96
Third International Conference on Porous Media and its Applications in Science, Engineering and IndustryJune 20-24, 2010, Tuscany, Italy
We had organized and held two highly successful conferences on Porous Media and its Applications in Science, Engineering and Industry were held in 1996 in Kona, Hawaii, and in 2007 in Kauai, Hawaii, which were attended by various researchers in porous media worldwide. This conference will build on the last two conferences so that it reflects the research done internationally in the currently active areas of the topic. The presence of the highly successful Journal of Porous Media and both editions of the very well received Handbook of Porous Media will act as an additional impetus to further galvanize this conference. Papers of high quality will be considered for submission to the Journal of Porous Media.
The pioneering works in the area of fluid transport as well as some aspects of heat transport in porous media go back to the beginning of this century. Convective heat transfer in fluid-saturated porous media has gained considerable attention in recent decades due to its relevance in a wide range of applications such as thermal insulation engineering, water movements in geothermal reservoirs, heat pipes, underground spreading of chemical waste, nuclear waste repository, geothermal engineering, grain storage and enhanced recovery of petroleum reservoirs. Radiative heat transfer and multiphase transport processes in porous media, both with and without phase change, have gained extensive attention in recent years. This is due to the wide range of applicability of these research areas in contemporary technology. These applications include, but are not restricted to, areas such as geothermal engineering, building thermal insulation, chemical catalytic reactors, packed cryogenic microsphere insulation, petroleum reservoirs, direct contact heat exchangers, coal combustors, nuclear waste repositories, and heat pipe technology.
Several applications related to porous media require a detailed analysis of convective heat transfer in different geometrical shapes, orientations and configurations. Based on the specific applications, the flow in the porous medium may be internal or external. Most of the studies in porous media carried out until the past two decades are based on the Darcy flow model, which in turn is based on the assumption of creeping flow through an infinitely extended uniform medium. However, it is now generally recognized that non-Darcian effects are quite important for certain applications. Different models have been introduced for studying and accounting for such non-Darcian effects as the inertial, boundary, and variable porosity effects. The ultimate goal of studies in convective heat transfer in porous media is to determine the dimensionless heat transfer coefficient, the Nusselt number. A considerable amount of research has been carried out to accomplish this, and empirical correlations for the Nusselt number for a variety of configurations and boundary conditions have been established, with certain limitation, of a wide variety of current technological applications. Many industrial operations in the areas of chemical and metallurgical engineering involve the passage of a fluid stream through a packed bed of particulate solids to obtain extended solid fluid interfacial areas or good fluid mixing. Typical examples of applications involving such systems include catalytic and chromatographic reactions, packed absorption and distillation towers, ion exchange columns, packed filters, pebble-type heat exchanger, petroleum reservoirs, geothermal operations and many others. The design of these systems is decided by mechanisms of pressure drop, fluid flow and heat and mass transfer governing the process in the packed bed arrangement. Considerable attention has been paid to the aforementioned aspects because of their direct influence on the optimization and stability of the design of these systems.
Developments in modeling transport phenomena in porous media have advanced several pertinent areas, such as biology. As such the conference will also entertain papers related to bio transport in porous media as well as research related to turbulent modeling in porous media.
97-101