Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
6
4
2003
Filling of a System of Channels and Porous Medium: An Effectiveness Factor Based on Momentum Transfer
The physics of the filling process of a porous media/channel network is governed by two groups of parameters. They are (1) the geometric dimensions of the porous medium and the channel network and (2) the flow parameters of the porous medium and the channel network. Their form has been identified and numerical studies have been conducted in order to investigate their influence on the filling process. An analytical model, called the filling-time ratio model, has been developed which depends on the filling time ratio and the filling modulus. Filling time ratio is the ratio of the time it takes to fill the channel network as compared to the overall geometry filling time. Filling modulus is defined in terms of permeabilities and geometric dimensions. The analytic model addresses isotropic as well as orthotropic porous media. The filling time ratio can be regarded as an effectiveness parameter of the system in which momentum transfer occurs. Thus, from the filling-time ratio model, one can either estimate the effectiveness of the system to transfer the momentum or choose the process material, or geometric parameters to obtain the desired effectiveness of the system. This filling-time ratio concept can be generalized and extended to other momentum transfer processes.
B.
Markicevic
Department of Mechanical Engineering, Kettering University, Flint, Michigan 48504, USA
Dirk
Heider
Center for Composite Materials, and Department of Electrical and Computer Engineering, University of Delaware, Newark, Delaware 19716, USA
Suresh G.
Advani
Center for Composite Materials, Department of Mechanical Engineering, University of Delaware, Newark, DE 19716
12
An Analysis of the Swimming Problem of a Singly Flagellated Microorganism in a Fluid Flowing through a Porous Medium
The present work is concerned with the study of the swimming of flagellated microscopic organisms, which employ a single flagellum for propulsion in a fluid flowing through a porous medium. The flow is modeled by appropriate equations and the organism is modeled by an infinite flexible but inextensible transversely waving sheet, which represents approximately the flagellum. The equations of motion are solved subject to the boundary conditions, and expressions for the velocity of propulsion of the microscopic organism are obtained. Certain allied cases involving the viscosity in combination with the effective viscosity of the medium are also investigated. A creeping flow model is also analyzed. Finally, purely from a mathematical standpoint, all cases with large permeability are shown to follow the results of swimming of such organisms in a viscous fluid (discounting the pores).
Abdul Majeed
Siddiqui
Department of Mathematics, Pennsylvania State University, York Campus, 1031 Edgecomb Avenue, York, PA 17403, USA
A. R.
Ansari
Department of Mathematics & Statistics, College of Informatics & Electronics, University of Limerick, Limerick, Ireland
8
A Model for Multiphase Flows through Poroelastic Media
A continuum model for multiphase fluid mixture flows through poroelastic media is presented. The basic conservation laws developed via a volume averaging technique are considered. Effects of phasic equilibrated forces are included in the model. Based on the thermodynamics of the multiphase mixture flows, appropriate constitutive equations are formulated. The entropy inequality is exploited, and the method of Lagrangian multiplier is used along with the phasic conservation laws to derive the constitutive equations for the phasic stress tensors, equilibrated stress vectors, and the interactions terms. The special cases of wave propagation in poroelastic media saturated with multiphase fluids, and multiphase flows through porous media, are studied. It is shown that the present theory leads to the extended Darcy’s law and contains, as a special case, Biot’s theory of saturated poroelastic media.
Goodarz
Ahmadi
Mechanical and Aeronautical Engineering Department, Clarkson University, Potsdam, NY 13699-5725, USA
Ali Reza
Mazaheri
Mechanical and Aeronautical Engineering Department, Clarkson University, Potsdam, NY 13699-5725; and National Energy Technology Laboratory, U.S. Department of Energy, Morgantown, WV 26507-880, USA
Duane H.
Smith
National Energy Technology Laboratory, U.S. Department of Energy, Morgantown, WV 26507-880, USA
14
Effects of Heterogeneity in Forced Convection in a Porous Medium: Parallel-Plate Channel, Brinkman Model
The effects of variation (in the transverse direction, in layers) of permeability and thermal conductivity, on fully developed forced convection in a parallel-plate channel filled with a saturated porous medium, is investigated analytically on the basis of a Brinkman model, for the case of isoflux boundaries and a two-step variation. The results demonstrate that the effect of permeability variation is that an above-average permeability near the walls leads to an increase in Nusselt number, and this is explained in terms of variation in the curvature of the temperature profile. This effect of permeability variation becomes less important as the Darcy number increases. The effect of conductivity variation is more complex; there are two opposing effects and the Nusselt number is not always a monotonic function of the conductivity variation. This effect of conductivity variation retains its importance as the Darcy number increases.
D A
Nield
10
Sensitivity and Selectivity of Porous Tape Cast Material for Gas Moisture Sensing
One of the most popular and widely used fabrication processes for making thin ceramics is the tape casting technique, which is used to produce porous tapes for studying moisture content in gases. Pore size and distribution have been analyzed from an SEM picture by an image analyzer. These data were then compared with the uniaxially pressed disc-type sample and a sample prepared by porous, thick film paste. Compared to the other techniques used, pore size distribution could be much more accurately controlled using tape casting. This distribution, in turn, has a large controlling effect on the range and sensitivity of the measurement of gas moisture.
Kalyan Kr.
Mistry
Electroceramics Division, Central Glass and Ceramic Research Institute, Jadavpur, Calcutta, 700 032, India
Santanu
Basu
Electroceramics Division, Central Glass and Ceramic Research Institute, Jadavpur, Calcutta, 700 032, India
Suman
Chatterjee
Electroceramics Division, Central Glass and Ceramic Research Institute, Jadavpur, Calcutta, 700 032, India
Manjushree
Saha
Electroceramics Division, Central Glass and Ceramic Research Institute, Jadavpur, Calcutta, 700 032, India
Debdas
Chattopadhyaya
Electroceramics Division, Central Glass and Ceramic Research Institute, Jadavpur, Calcutta, 700 032, India
Kamalendu
Sengupta
Electroceramics Division, Central Glass and Ceramic Research Institute, Jadavpur, Calcutta, 700 032, India
6
The Darcy Model for Boundary Layer Flows in a Horizontal Porous Medium Induced by Combined Buoyancy Forces
A comparative study on combined heat mass transfer by natural convection along the horizontal surface in a fluid saturated porous medium is reported. The Von-Karmann integral method and similarity method have been employed for the solution to the problem where the wall temperature and concentration are a power function of distance from the origin. The structure of flow, temperature and concentration fields are governed by the parameters like the buoyancy ratio (B) and Lewis number (Le). Results for the physical quantities are presented for wide range of these parameters and the velocity, temperature and concentration profiles and constructed.
Virendra
Bansod
Department of Mathematics, Dr. B. A. Technological University, Lonere, India
9