Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
16
9
2013
PORE-SCALE SIMULATION OF LAMINAR FLOW THROUGH A SAMPLE OF ALUMINUM FOAM
Open-cell metal foams are used in a growing number of applications like lightweight porous structures, enhanced heat transfer devices and compact heat exchangers, catalytic reactors, and even rotors of centrifugal compressors. In many cases, pressure drops and flow rates through the metal foams are predicted using the macroscopic Darcy−Forchheimer equation. Values obtained can be accurate enough for applications, provided the hydraulic properties of the foam are known. The present work is aimed to describe a numerical approach for calculating the hydraulic permeability and the Ergun coefficient of a real sample of metal foam starting from an x-ray tomography of the sample. Fluid dynamic simulations are conducted in the digital sample at the scale of the pores and data obtained are postprocessed to obtain the main hydraulic properties of the porous material.
Marzio
Piller
Department of Engineering and Architecture, University of Trieste, Trieste, 34127, Italy
Alberto
Boschetto
Dipartimento di Meccanica e Aerospaziale, Università di Roma La Sapienza, 00184 Roma, Italy
Enrico
Stalio
Dipartimento di Ingegneria "E. Ferrari", Università di Modena e Reggio Emilia, 41125 Modena, Italy
Gianni
Schena
Department of Engineering and Architecture, University of Trieste, Trieste, 34127, Italy
Orsola
Errico
Dipartimento di Ingegneria "E. Ferrari", Università di Modena e Reggio Emilia, 41125 Modena, Italy
777-793
CLOSED-FORM SOLUTIONS FOR UNSTEADY MAGNETOHYDRODYNAMIC FLOWIN A POROUS MEDIUM WITH WALL TRANSPIRATION
This problem deals with an unsteady two-dimensional magnetohydrodynamic flow of incompressible viscous fluid over a flat plate with wall transpiration embedded in a porous medium. Exact solutions corresponding to the Stokes first and second problems are obtained using an extended separation of variable technique together with the similarity arguments. The corresponding starting solutions are presented as the sum of steady state and transient solutions. Further, it is found that for small time t the difference between the steady state and the transient solutions is significant. However, for large values of t, both of these solutions become identical. These solutions do not involve any unevaluated integral and are expressed in terms of exponential and complementary error functions. Effects of the material parameters on the velocity fields are investigated by plotting the graphs. The nature of the wall shear stress engendered due to the flow is also studied by presenting the results in graphical and tabular forms. Some well-known and fundamental solutions existing in the literature are also obtained as the limiting cases of our solutions.
Mohammed
Abdulhameed
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia 81310, Skudai, Malaysia
Ilyas
Khan
Majmaah University
Arshad
Khan
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia 81310, Skudai, Malaysia; Department of Computer Science/IT Sarhad University of Science & IT, Peshawar Khyber Pakhtunkhwa Pakistan
Sharidan
Shafie
Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia
81310, UTM Skudai
795-809
NUMERICAL INVESTIGATION OF ENTROPY GENERATION FOR DOUBLE-DIFFUSIVE CONVECTION WITH SORET EFFECT IN A SQUARE POROUS CAVITY USING DARCY−BRINKMAN MODEL
The objective of the present work is to numerically study the Soret effect on entropy generation in a square porous cavity saturated by a binary perfect gas mixture and submitted to horizontal thermal and concentration gradients, using the Darcy−Brinkman model. The control volume finiteelement method was used to solve the set of coupled equations of mass, momentum, energy, and species conservation. Influence of the Soret effect on the irreversibility was studied by the variation of the thermal diffusion ratio, the Darcy number, the thermal porous Rayleigh number, and the buoyancy ratio. It was found that entropy generation is driven by heat transfer, diffusion or viscous irreversibility according to thermal diffusion ratio, the buoyancy ratio, and the Darcy number values.
Nejib
Hidouri
Gabès University, Chemical and Process Engineering Department, Engineers National School of Gabès, Applied Thermodynamics Unit, Tunisia
Ali
Mchirgui
Ph.D
Mourad
Magherbi
Chemical and Process Engineering Department, Engineers National School of Gabes, Gabes University, Applied Thermodynamics Unit, Omar Ibn El Khattab St., 6029 Gabes, Tunisia
Ammar Ben
Brahim
Gabès University, Chemical and Process Engineering Department, Engineers National School of Gabès, Applied Thermodynamics Unit, Tunisia
811-822
ENTROPY ANALYSIS OF UNSTEADY MAGNETIC FLOW THROUGH A POROUS PIPE WITH BUOYANCY EFFECTS
The paper focuses on first and second law analyses for flow and heat transfer inside a uniformly porous vertical pipe. The pipe flow is subjected to a constant suction at the wall and is acted upon by a combination of buoyancy forces, a transverse magnetic field, and constant pressure gradient. The pipe walls are kept isothermal and the flow of the conducting fluid is assumed to be unsteady with variable viscosity. The nonlinear governing equations in cylindrical coordinates are obtained under axisymmetric assumptions and solved numerically using semi-implicit finite difference techniques to obtain expressions for the velocity and temperature profiles. The entropy generation number, irreversibility distribution ratio, and Bejan number are presented graphically and discussed quantitatively for various values of the embedded parameters.
Tirivanhu
Chinyoka
Center for Research in Computational and Applied Mechanics, University of Cape Town
Oluwole Daniel
Makinde
Faculty of Military Science, Stellenbosch University, Private Bag X2, Saldanha 7395, South Africa
Adetayo S.
Eegunjobi
Department of Mathematics and Statistics, Namibia University of Science and Technology, Windhoek, Namibia
823-836
LATTICE BOLTZMANN METHOD FOR MODELLING HEAT AND MASS TRANSFERS DURING DRYING OF DEFORMABLE POROUS MEDIUM
The present paper deals with heat and mass transfer during drying of a deformable saturated porous medium. The
considered sample walls are maintained to a convective heat flux. The water is evaporated via the top and bottom walls of the sample. In modelling the liquid flow, the Darcy−Brinkmann extended model is incorporated in the momentum equation. Therefore the solid deformation is assumed to be characterized by a modified Darcy model. The model for the energy equation was based on the local thermal equilibrium assumption, between the liquid and the solid phases. The lattice Boltzmann method (LBM) is used to solve the differential system of equations. A comprehensive analysis of the influence of the Darcy number, the thermal conductivity ratio, and the heat capacity ratio on macroscopic fields is investigated throughout this work.
Hussein
El Abrach
Monastir University, National School of Engineers, Ibn Eljazzar Street, 5019, Monastir, Tunisia
Hacen
Dhahri
Laboratoire d'Etudes des Systèmes Thermiques et Energétiques, Université de Monastir, Ecole Nationale d'Ingénieurs de Monastir, Rue Ibn Eljazzar, 5019 Monastir, Tunisia
Abdallah
Mhimid
Laboratoire d'Etudes des Systèmes Thermiques et Energétiques, Université de Monastir, Ecole Nationale d'Ingénieurs de Monastir, Rue Ibn Eljazzar, 5019 Monastir, Tunisia
837-855
PYROLYSIS IN POROUS MEDIA: PART 2. NUMERICAL ANALYSIS AND COMPARISON TO EXPERIMENTS
Only limited studies are available experimentally to investigate hydrocarbon fuel pyrolysis, which can be of practical interest for the active cooling of head-loaded components in aerospace vehicles such as combustors in rocket engines. The numerical simulation is an additional way to investigate the related phenomena (heat and mass transfer with chemistry). After a first-code validation with experiments based upon inert gases, the code is further extended toward permeation with reactive dodecane and a reasonable agreement is found. The experimental accuracy of the permeability's' determination
is confirmed numerically to be within ±30%. Numerically it is shown that this accuracy is due to strong flow spatial heterogeneities. The border effect of the test cell is found to be related to the permeable medium thickness, whereas the temperature field is correlated to the reaction zone. Two different kinetic mechanisms are used to investigate the chemistry effect on the heat and mass transfer. They also provide a better analysis of the fuel pyrolysis and of the products' formation.
Nicolas
Gascoin
PRISME Laboratory, INSA-Centre Val de Loire, 88 boulevard Lahitolle, 18000 Bourges, France
Luigi
Romagnosi
University of Orléans, Bourges, 18000, France and University of Rome, La Sapienza, Rome, 00184, Italy
Ivan
Fedioun
ICARE-CNRS 1C avenue de la Recherche Scientifique, F-45071 Orleans cedex 2, France
Johan
Steelant
Section of Aerothermodynamics ESTEC-ESA, P.O. Box 299, 2200 AG Noordwijk, The Netherlands
Guillaume
Fau
PRISME Laboratory, INSA-Centre Val de Loire, 88 boulevard Lahitolle, 18000 Bourges, France
Marc
Bouchez
MBDA-France, 18 rue Le Brix, 18000 Bourges, France
857-873