Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
16
7
2013
APPLICABILITY OF ARTIFICIAL NEURAL NETWORKS TO PREDICT EFFECTIVE THERMAL CONDUCTIVITY OF HIGHLY POROUS METAL FOAMS
This paper presents the applicability of artificial neural networks to predict effective thermal conductivity of highly porous metal foams. Artificial neural network models are based on feedforward backpropagation network with training functions such as gradient descent (GD), gradient descent with adaptive learning rate (GDA), gradient descent with momentum (GDM), gradient descent with momentum and adaptive learning rate (GDX), and scaled conjugate gradient (SCG). Volume fraction of fluid phase and thermal conductivity of solid and fluid phases are input parameters for the artificial neural network to predict the effective thermal conductivity. The training algorithm for neurons and hidden layers for different feedforward backpropagation networks runs at the uniform threshold function TANSIG-PURELIN for 500 epochs. Better agreement of predicted effective thermal conductivity values is obtained by using artificial neural networks with the experimental results. A comparison with other models is also made and it is found that the values of effective thermal conductivity predicted by using the present model are in good agreement with the reported experimental values.
Rajpal S.
Bhoopal
Thermal Physics Laboratory, Department of Physics, University of Rajasthan, Jaipur 302 055, India
P. K.
Sharma
Thermal Physics Laboratory, Department of Physics, University of Rajasthan, Jaipur 302 055, India
Ramvir
Singh
Thermal Physics Laboratory, Department of Physics, University of Rajasthan, Jaipur 302 055, India
R. S.
Beniwal
CSIR-National Institute of Science Communication and Information Resources, New Delhi 110 012, India
585-596
SIMULATION OF VORTEX RING PERMEATION IN POROUS MEDIA
This study presents a numerical analysis of a two-dimensional vortical flow propagating through an isotropic, rigid, homogeneous porous medium. The vortical flow is produced by a piston-cylinder vortex ring generator. The objective is to understand the flow behavior in porous media as a function of impingement velocity and porous media properties, specifically, porosity and permeability. Results show that the formation of vortices and flow pattern in porous media strongly depend on permeability but have only a weak dependence on the porosity and Reynolds number. Furthermore, the average vorticity over the porous medium is calculated for various velocities, porosities, and permeabilities. The results show that for laminar flow injection, the average vortivcity is not influenced by either porosity or permeability of the domain. However, for high Reynolds flow velocity, permeability and porosoity both play significant roles on the magnitude of the overall vorticity.
Fatemeh
Hassanipour
Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX, 75080
Isaac P.
Raya
Department of Mechanical Engineering, University of Guanajuato, Salamanca Gto., Mexico
S. Negin
Mortazavi
Department of Mechanical Engineering, University of Texas at Dallas, Texas, USA
597-605
GAS DIFFUSIVITY IN POROUS MEDIA: DETERMINATION BY MERCURY INTRUSION POROSIMETRY AND CORRELATION TO POROSITY AND PERMEABILITY
Much effort has been extended on diffusivity measurement because diffusion can dominate mass transport in porous media of low hydraulic conductivity. The main purpose of this work is to derive the gas diffusivities of building materials, rocks and sediments using the average pore size measured by mercury intrusion porosimetry (MIP). MIP has been utilized for decades to obtain the poresize distribution of porous media. We performed triplicate MIP tests on concrete and Berea sandstone to evaluate the repeatability of MIP data. Gas diffusivity results are consistent with literature data using the gas diffusion methods. Our results show that the relationship between gas diffusivity and porosity is analogous to Archie's law and that two groups of rocks are differentiated according to the cementation factor m value in an Archie's-type relationship. It also appears that gas diffusivity exhibits an increasing trend with an increase of permeability, and two different exponential relationships exist between permeability and porosity for these two groups of rocks.
Zhiye
Gao
China University of Petroleum-Beijing
Qinhong
Hu
Department of Earth and Environmental Sciences, University of Texas at Arlington, Arlington, Texas 76019, USA
Hecheng
Liang
School of Environmental Studies, China University of Geosciences, Wuhan, 430074, China
607-617
MASS TRANSFER IN TWO MHD VISCOELASTIC FLUIDS OVER A SHRINKING SHEET IN POROUS MEDIUM WITH CHEMICAL REACTION SPECIES
An analysis is carried out to study the mass transfer in the MHD flow for two viscoelastic fluids over a permeable shrinking sheet through a porous space in the presence of chemical reaction. The reaction of species is to be taken as nth-order homogeneous chemical reaction of constant rate. The resultant nonlinear partial differential equations are reduced to the system of nonlinear ordinary differential equations by using similarity transformations. The purely analytic solution of velocity and the concentration fields are obtained by means of the homotopy analysis method (HAM). The influences of the involving parameter on the velocity and the concentration profiles are shown through graphs and discussed in detail. The numerical values of the skin-friction coefficient and the surface mass transfer for various parameters are also given in tabular form. Comparison of both analytic and exact solutions is given and found in good agreement.
Zaheer
Abbas
Department of Mathematics, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
Mariam
Sheikh
Department of Mathematics, Riphah International University, Islamabad 44000, Pakistan
Muhammad
Sajid
Department of Mathematics and Statistics, International Islamic University, Islamabad 44000, Pakistan
619-636
THE CHENG-MINKOWYCZ PROBLEM FOR THE TRIPLE-DIFFUSIVE NATURAL CONVECTION BOUNDARY LAYER FLOW PAST A VERTICAL PLATE IN A POROUS MEDIUM
We consider in this paper the extension of the Cheng-Minkowycz boundary layer problem past a vertical plate in a porous medium in the presence of more than one (triple) chemical dissolved in fluid mixtures using the Darcy porous medium model. Both the buoyancy aiding and opposing flows are investigated. Using appropriate similarity variables, the governing partial differential equations are reduced to ordinary (similarity) differential equations, which are then solved numerically using a Fehlberg fourth−fifth order Runge-Kutta method. Comparison with the results reported in Bejan and Khair (1985) [Bejan, A. and Khair, K. R., Heat and mass transfer by natural convection in a porous medium, Int. J. Heat Mass Transfer, vol. 28, pp. 909−918, 1985] is made and it is found an excellent agreement. Results for the flow, heat, and concentration characteristics are presented graphically and in tabular form and then discussed.
Waqar A.
Khan
Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1 Canada
Ioan
Pop
Department of Applied Mathematics, Babes-Bolyai University, 400084 Cluj-Napoca, Romania
637-646
POWER-LAW FLUID FLOWS IN CHANNELS WITH A PERMEABLE WALL
The flow of an incompressible non-Newtonian fluid limited by two impermeable flat plates is studied by considering two distinct flow regions: one with the fluid only (without a porous matrix) and the second one with this fluid flowing through a porous medium. A mixture theory model is employed to describe these two adjacent flow regions in which the fluid has a power-law behavior. Adequate compatibility conditions at the interface between the two regions are considered. Numerical simulations have been performed employing a Runge-Kutta methodology coupled with a shooting strategy. Such problem is interesting in order to verify the coupled influence of material parameters and compatibility conditions. Employing this numerical strategy, the solution of the problem is essentially reduced to finding the root of a real function. The flow behavior for distinct values of the power-law index, characterizing what is usually referred as shear-thinning and shear-thickening fluids, was investigated. Comparison with some limit cases has validated the numerical procedure.
Maria Laura
Martins-Costa
Laboratory of Theoretical and Applied Mechanics (LMTA) Mechanical Engineering Graduate
Program (TEM-PGMEC), Universidade Federal Fluminense, Rua Passo da Pátria, 156,
24210-240, Niterói, RJ, Brazil
Jesus Alfonso Puente
Angulo
Laboratory of Theoretical and Applied Mechanics, Graduate Program in Mechanical
Engineering, Universidade Federal Fluminense, 24210-240, Niterói, RJ, Brazil; Department of Mechanical Engineering, Federal Center of Technological Education of Rio de
Janeiro, Angra dos Reis, RJ, Brazil
Heraldo S.
da Costa Mattos
Laboratory of Theoretical and Applied Mechanics (LMTA), Graduate Program in Mechanical Engineering (PGMEC), Universidade Federal Fluminense (UFF), Rua Passo da Patria, 156, 24210-240 Niteroi, RJ, Brazil
647-661
VISCOUS CORRECTIONS FOR THE VISCOUS POTENTIAL FLOW ANALYSIS OF MAGNETO-HYDRODYNAMIC KELVIN-HELMHOLTZ INSTABILITY THROUGH POROUS MEDIA
Viscous corrections for the viscous potential flow analysis of Kelvin-Helmholtz instability at the interface of two incompressible, viscous, and electrically conducting fluids has been carried out. The fluids are flowing through porous media between two rigid planes and they are subjected to a constant magnetic field parallel to the streaming direction. In viscous potential flow theory, viscosity enters through normal stress balance and the effect of shearing stresses is completely neglected. We include the viscous pressure in the normal stress balance along with irrotational pressure and it is assumed that this viscous pressure will resolve the discontinuity of the tangential stresses at the interface for two fluids. A dispersion relation has been derived and stability is discussed theoretically as well as numerically. The stability criterion is given in terms of a critical value of relative velocity as well as the critical value of applied magnetic field. It has been observed that a tangential magnetic field has a stabilizing effect on the stability of the system while a porous medium destabilizes the interface. Also, it has been found that the effect of irrotational shearing stresses stabilizes the system.
Mukesh Kumar
Awasthi
Department of Mathematics, University of Petroleum and Energy Studies, Dehradun-248007, (Uttarakhand), India
Mohammad
Tamsir
Department of Mathematics, Graphic Era University, Dehradun
663-676
GENERALIZATION OF THE SURFACE TRACTION DEPENDENCE OF INTERACTIONS BETWEEN PORES/HOLES VIA A PECULIAR INSTANCE OF SUPERPOSITION OF APPLIED STRESSES AND RESULTANT STRAIN ENERGIES
The existing formulae for the elastic repulsions between equi-sized/equi-pressurized pores/holes are generalized to include any combination of hole surface tractions. This is done utilizing an exceptional case where superposition can be used for applied stresses and resultant strain energies.
Kostas
Davanas
Hellenic Civil Aviation Authority, 17, Amfanon Str., Volos 38500, Greece
679-681