Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
15
7
2012
A NUMERICAL STUDY OF THE DESALINATION SOIL BY DRY DRAINAGE PROCESS
The excessive increase of salt in soil is considered as a major contemporary threat. Among the significant causes of this phenomenon are evaporated and/or transpired irrigation water, which contribute directly to the accumulation of salt ions in the soil. To tackle this salient problem many methods have been advocated. The first tends to eliminate salts by combining the leaching requirement method together with artificial drainage. However, it has proven to be inadequate. The second, a recent and novel one, aims at capturing and removing salt from the soil surface. This process is referred at as the dry drainage method. This work is a numerical simulation of the simultaneous water solute and heat transfer in an unsaturated porous medium during the simultaneous evaporation and drainage of saline dry land soils. A detailed mathematical model is formulated to describe the non-isothermal transport of water in unsaturated porous media. The model consists of the coupled conservative equations of mass, liquid phase, gas phase, water vapor, species, and energy. The water transport mechanisms dealt with are the liquid-phase advection and diffusion of vapor in the gas phase. The numerical results show the remarkable variation profiles of water evaporation and the distribution of soil solution and solute during desalination by dry drainage relative to previous models. In fact, the use of the stick system favors the evaporation intensity and the solute accumulates far from the soil surface layer.
M.
Adala
LETTM, The High Institute of Sciences and Technology of Hammam, Sousse, 4011, Tunisia; Département Génie Civil, Ecole Normale Supérieure de Cachan (ENS Cachan), 61 Avenue du Président Wilson, 94235 Cachan Cedex, France
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 PrĂ©sident Wilson, 94235 Cachan Cedex, France
Habib
Sammouda
LabEM, LR11ES34, Sousse University,Tunisa, ESSTHS, rue LamineAbbassi, 4011-H.Sousse-Tunisia
607-615
INVESTIGATION OF SIMULTANEOUS EFFECTS OF GYROTACTIC AND OXYTACTIC MICROORGANISMS ON NANOFLUID BIO-THERMAL CONVECTION IN POROUS MEDIA
This paper develops a theory of nanofluid bio-thermal convection in a fluid-saturated porous layer when the suspension contains two different species of motile microorganisms. The goal is to investigate the combined effect of these two species of microorganisms, nanoparticles, and a vertical temperature variation on the hydrodynamic stability of the layer. Since microorganisms are heavier than the base fluid (water) and swim in the upward direction, they act as a destabilizing agency. It is interesting that if one species of microorganisms is present, the system becomes less sensitive to the concentration of the second species, as long as the concentration of the second species of microorganisms remains small. The effect of the nanoparticles depends on whether their distribution is top heavy or bottom heavy. The effect of the temperature variation is destabilizing when heating from the bottom and stabilizing when cooling from the bottom. The utilization of the linear instability theory makes it possible to decouple the effects of these various agencies and obtain an eigenvalue equation that involves four Rayleigh numbers, each characterizing one of the effects described above.
Andrey V
Kuznetsov
Department of Mechanical and Aerospace Engineering, North Carolina State University, Campus Box 7910, Raleigh, NC 27695-7910, USA
Valeri
Bubnovich
Department of Chemical Engineering, Universidad de Santiago de Chile, 3363 B. O'Higgins, Santiago, Chile
617-631
MODELING OF CONDUCTIVE HEAT TRANSFER IN LOW-DENSITY PVC FOAMS UNDER MECHANICAL LOAD
Due to their excellent thermal insulation properties, low-density polyvinyl chloride (PVC) foams find applications in a wide variety of technological fields. They are notably used as thermal insulation in fuel tanks of Ariane rockets at very low temperatures. For this application, a relatively high mechanical strength is also required since the foams undergo significant mechanical loads during the flight. As a consequence, the mechanical strain undergone by the foams may affect their thermal behavior and vice versa, leading to a coupling between the mechanical and thermal properties. That is the reason why, in order to improve the modeling of the mechanical and thermal behaviors and to better understand their mutual influences, an original thermal model has been developed that is based on a shell mesh of the porous structures of PVC foams obtained by X-ray tomography. This permits the quick computation of the temperature field prevailing in the solid and fluid phases constituting the material and of the equivalent thermal transfer properties. The temperature field and thermal properties could then be used as entrance data of a mechanical finite-element computation. The effective thermal conductivities computed for non-deformed structures were compared with various correlations in the literature. Thereafter, the numerical model was applied to deformed structures obtained from mechanical finite-element computations modeling various mechanical loads. The analysis of the results highlights the major modifications of the thermal properties brought by different types of mechanical loads.
Dominique
Baillis
LaMCoS, INSA-Lyon, CNRS UMR 5259,18-20 Rue des Sciences, F69621 Villeurbanne, France
Remi
Coquard
Société "Etude Conseils Calcul Modélisation" (EC2-MODELISATION), 66 Boulevard Niels Bohr, F69603 Villeurbanne, France
P. M. M.
Michaud
Etude Conseils Calcul en Mécanique des Structures (EC2MS) Company, 66 Boulevard Niels Bohr, 69603 Villeurbanne CEDEX, France
W.
Rambaud
CRYOSPACE (EADS Astrium) Company, 59 Route de Verneuil, 78130 Les Mureaux, France
F.
Peyraud
CRYOSPACE (EADS Astrium) Company, 59 Route de Verneuil, 78130 Les Mureaux, France
J.
Haviez
CRYOSPACE (EADS Astrium) Company, 59 Route de Verneuil, 78130 Les Mureaux, France
633-646
MODELING OF HEAT TRANSFER ACROSS POROUS HONEYCOMB STRUCTURES
In the framework of the reduction of the weight of airplanes, porous honeycomb structures are increasingly used in the aircraft industry. They notably enter in the composition of the new generation composite fuselages as thermal insulating shields due to interest in combining, at the same time, high thermal insulating properties, low density, and sufficient mechanical resistance. However, their thermal properties remain relatively unexplored and the number of theoretical and experimental studies concerning the heat transfer through honeycomb structures is very limited. Therefore, the present study is interested in the modeling of the complete heat transfer through this type of porous material. Due to their low density, both conductive and radiative heat transfers have to be taken into account while the contribution of convection can be neglected. The coupled heat transfer is solved by a numerical resolution of the combined energy and radiative transfer equations. The equivalent radiative properties of the material are determined using ray-tracing procedures inside the idealized porous structure while the effective conductivity is estimated via simple, but nonetheless, realistic analytical formulas. The accuracy of the developed model is validated by comparing the heat transfer coefficient measured by different authors for various honeycomb structures with the theoretical results. Thereafter, a parametric study is conducted by varying the structural dimensions and physical properties of the constituents. This permits us to evaluate the contributions of radiative and conductive heat transfers and to highlight the parameters that strongly influence the thermal performance of the insulating shield.
Dominique
Baillis
LaMCoS, INSA-Lyon, CNRS UMR 5259,18-20 Rue des Sciences, F69621 Villeurbanne, France
Remi
Coquard
Société "Etude Conseils Calcul Modélisation" (EC2-MODELISATION), 66 Boulevard Niels Bohr, F69603 Villeurbanne, France
M.
Thomas
Airbus Operation SAS, 316 Route de Bayonne, 31060 Toulouse, France
B.
Estebe
Airbus Operation SAS, 316 Route de Bayonne, 31060 Toulouse, France
647-663
EFFECTS OF FINES MIGRATION ON WELL PRODUCTIVITY DURING STEADY STATE PRODUCTION
Well clogging and productivity decline have been widely observed in oil, gas, and artesian wells producing reservoir fines. The phenomenon has been explained by the lifting, migration, and subsequent plugging of the pores by the fine particles, finally resulting in permeability decrease. This has been observed in numerous core flood tests and field cases. In this work, the new basic equations for the detachment of fine particles, their migration, and size exclusion, causing the rock permeability decline, have been derived. The analytical model, developed for the regime of steady-state production with the gradual accumulation of strained particles, exhibits the linear skin factor growth versus the amount of produced reservoir fines. The modeling data are in good agreement with the well production history. The model allows predicting well productivity decline due to fines production based on short-term production data.
Abbas
Zeinijahromi
Australian School of Petroleum, The University of Adelaide, Adelaide, SA 5005, Australia
Alexandre
Vaz
North Fluminense State University of Rio de Janeiro UENF, Rio de Janeiro, Brazil
Pavel
Bedrikovetsky
Australian School of Petroleum, The University of Adelaide, Adelaide, SA 5005, Australia
Sara
Borazjani
Australian School of Petroleum, The University of Adelaide, Adelaide, SA 5005, Australia
665-679
PHOTOCONDUCTIVITY TIME RESPONSE OF Ti NANOCOLUMNS FABRICATED BY THE GLAD METHOD
The aim of this work is to present a physical method of Ti nanocolumn fabrication on glass substrates, referred to as glancing angle deposition (GLAD). For precise and controllable evaporation, an electron beam evaporation system has been used. Scanning electron microscope micrographs from plan and cross section samples confirmed the fabrication of Ti nanocolumns. In addition, we have studied the photoconductivity (PC) of Ti nanocolumns. We have measured the PC time response for three voltages: 0, 1, and 2 V. Our results in all voltages show that there is similar behavior for time response. Meanwhile, there are two slopes for the PC time response in each external bias voltage. Also, our PC measurement showed that the PC current decreases with enhancement of the tilt angle in each voltage. The results are quite different compared with bulk Ti and confirm that Ti nanocolumns have different properties with respect to the bulk samples.
Reza S.
Dariani
Department of Physics, Alzahra University, Tehran, 19938, Iran
S.
Farokhipoor
Department of Physics, Alzahra University, Tehran, 19938, Iran
683-688
ANALYTICAL SOLUTION OF SLOW FLOW PAST A HETEROGENEOUS POROUS SPHERE WITH RADIAL VARIATION OF PERMEABILITY USING BRINKMAN MODEL
In the present paper, the slow flow of an incompressible viscous fluid past a heterogeneous porous sphere with radial variation of permeability is considered. The flow in the free fluid region outside the sphere is governed by the Stokes equation. The flow within the porous region of the sphere is governed by Brinkman's law. The boundary conditions used at the interface are the continuity of the normal and tangential velocity and continuity of the normal and shear stress. An analytical solution to the momentum equations are obtained for the velocity and pressure fields in the Brinkman and Stokes flow regions for two cases: (1) when the sphere is of variable permeability and (2) when the sphere is of uniform permeability. Exact expressions for the drag on the sphere are obtained. The influence of the permeability variation parameters on the flow is discussed. Stream lines, radial velocity, and drag force on the sphere are exhibited graphically in the free fluid region and within the porous sphere for different values of the permeability parameter.
Vineet Kumar
Verma
Department of Mathematics and Astronomy University of Lucknow, Lucknow, INDIA-226007
Sunil
Datta
Department of Mathematics and Astronomy, University of Lucknow, Lucknow, India-226007
689-696
MHD COUETTE FLOWS OF SECOND GRADE FLUID IN A POROUS SPACE
This study investigates the influence of partial slip on the flows of second grade fluid bounded by the two rigid plates. An incompressible and magnetohydrodynamic second grade fluid occupies the porous space. Modeling of the flow analysis includes the modified Darcy's law. Two characteristic examples, flows induced by an oscillating plate and a suddenly moving plate, are considered. The exact analytical solutions are derived by employing Fourier transform and eigen-function expansion methods. It is noted that the results of previous studies can be obtained as the limiting cases of our solutions.
Tasawar
Hayat
Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000, Pakistan; Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science,
King Abdulaziz University, Jeddah 21589, Saudi Arabia
Chaudry Masood
Khalique
Department of Mathematical Sciences, International Institute for Symmetry Analysis and Mathematical Modelling, North West University, Mmabatho 2735, South Africa
Ahmed
Alsaedi
Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Department of Mathematics, Faculty of Science, King Abdulaziz University, P. O. Box. 80257,
Jeddah 21589, Saudi Arabia
697-704