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Ce travail est consacré à l’étude des transferts de chaleur dans une enceinte cubique remplie partiellement d’une matière poreuse et par un seul fluide. Le modèle mathématique utilisé est celui de Darcy – Brinkman – Forchheimer. Les équations modélisées de continuité, du mouvement, de l’énergie et de masse sont numériquement résolues par la méthode des volumes finis. On a étudié l’influence de la perméabilité et d’autres paramètres sur les transferts de chaleur. Les résultats obtenus montrent que le nombre de Nusselt augmente avec l’augmentation de la perméabilité pour différent nombre de Darcy, et il diminue avec l’augmentation de la couche poreuse. Les résultats numériques de notre étude sont en bon accord avec ceux de la littérature.

Ce travail porte sur une simulation numérique de la convection naturelle stationnaire, dans une enceinte de forme cubique. L’enceinte est partiellement poreuse homogène et isotrope. Les parois horizontales de l’enceinte sont adiabatiques imperméables. Les parois verticales de la cavité sont soumises à des températures constantes (des conditions aux limites de type Dirichlet), et le fluide est de l’air. L’écoulement dans le milieu poreux est modélisé par le modèle de Darcy-Brinkman-Forchheimer. La méthode numérique des volumes finis est utilisée pour la résolution des équations de continuité, de quantité de mouvement, et de l’énergie. Les résultats obtenues ont permis d’étudier l’influence des nombres de Rayleigh, de Darcy, et l’épaisseur adimensionnelle de la couche poreuse sur le transfert thermique. Les résultats obtenus indiquent que l’augmentation de Nu est proportionnelle à l’augmentation des nombres de Rayleigh et de Darcy et inversement proportionnelle à l’épaisseur adimensionnelle de la couche poreuse.

Copyright of Larhyss Journal is the property of Biskra University, Research Laboratory in Subterranean & Surface Hydraulics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the petroleum industry, understand the relationship among the parameters that optimize and develop the oil field is very important to optimize the economic returns of Petroleum Company. As well, the most economically profitable fields are the most easily accessible and simple to exploit. This simplicity is based mainly on a better understanding of the process in anisotropic rocks and their influence on the elastic modelling and characterization of naturally fractured reservoirs. In this context, among the main tasks of the reservoir engineer is to optimize production. Furthermore, it called on reliable tools, first to visualize the sub-surface in order to identify the location of potential reservoirs and to describe the geometric structure of a reservoir to predict dynamic behavior using software numerical simulation. The crux of the work presented in this article concerns a better understanding of the reservoir. And to do this, we are faced with the challenge to exploit a deemed useful tool in order to construct a representative model of the sub-surface reality from the available data. Based on the toolbox MRST (Matlab Reservoir Simulation Toolbox), we developed a scientific tool for estimating hydrocarbon reserves and to simulate the reservoir model and then predict how fluids flow through this model. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to establish the global regularity of classical solution for unidirectional flow of magnetohydrodynamic (MHD) Sisko fluid. The fluid is taken between two rigid plates. An incompressible fluid saturates the porous medium. The main interest in this paper is to establish the global regularity of classical solutions when , , and are sufficiently small. In addition, uniqueness of the classical solution is also verified. Here BMO denotes the homogeneous space of bounded mean oscillations, V is the velocity, u is the x-component of velocity, and is the vorticity. [ABSTRACT FROM AUTHOR]

Copyright of Larhyss Journal is the property of Biskra University, Research Laboratory in Subterranean & Surface Hydraulics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Notre travail présente une étude expérimentale du dépôt de particules colloïdales dans un milieu poreux consolidé, homogène et initialement saturé en eau. La phase fluide injectée dans le milieu poreux est une suspension de particules de latex dont la dimension est connue. L'influence de la force ionique de la suspension colloïdale et du débit d'injection sur le dépôt de particules est étudiée. On observe que le recouvrement de surface (θ) croît avec la force ionique alors que le recouvrement de surface (θ) décroît quand le nombre de Péclet augmente. Des mesures locales, par atténuation d'un rayonnement γ, mettent en évidence la réduction de porosité due au dépôt de particules. La réduction de la perméabilité, mesurée en fin d'expérience. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Chemical Engineering is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cet article est une contribution modeste à l’analyse des phénomènes complexes de transferts couplés de chaleur et de masse se produisant entre un gaz en mouvement et un solide humide. Il s’intéresse au séchage d’un fruit (les figues) déposé en lit profond et exposé à une convection forcée d’air. Le milieu se comporte comme étant poreux et ce sont, par conséquent, les équations de transferts dans un milieu poreux qui décrivent le transfert couplé de chaleur et de masse. L’étude est développée à l’échelle macroscopique avec un empilement de sphères du fruit. Le modèle utilisé est un modèle de séchage E.D.P (Equations aux Dérivées Partielles) basé sur les équations des bilans massique et énergétique et notamment sur l’utilisation des corrélations proposées pour la constante de séchage K avec l’hypothèse du Non Equilibre Thermique Local (N.L.T.E), mais aussi du modèle de Henderson et Pabis pour exprimer la cinétique de séchage. L’analyse théorique du séchage du lit statique mène à un ensemble d’équations aux dérivées partielles qui sont discrétisées par la méthode des différences finies. Pour la résolution de ce système d’équations, la méthode itérative de Gauss Seidel est utilisée et un code de calcul en Fortran est ensuite développé. Les résultats obtenus montrent l’absence de la phase constante de séchage et permettent de mettre en évidence les variations des paramètres de l’air d’une part et celles du produit séché d’autre part, au cours du séchage. Ils montrent aussi, que la vitesse de l’air n’est pas constante pendant le séchage d’où l’importance de la prise en considération du phénomène de rétrécissement et, d’autre part, ils montrent par la variation de la température de l’air, que l’énergie mise en jeu servant pour le transfert massique sert également pour le transfert thermique.

L’objet de cette étude est de caractériser le transfert de chaleur d’un écoulement turbulent dans un échangeur à plaques, muni d’une couche poreuse. Les parois sont maintenues à une température constante. Par ailleurs, l’écoulement est régi par les équations classiques de conservation (masse, énergie) et notamment l’équation moyennée de Darcy- Brinkman- Forchheimer. Cependant le tenseur de Reynolds est décrit par le modèle statistique en un seul point (k - ) a été adopté. Néanmoins, ce dernier a été modifié pour simuler l’écoulement turbulent en milieu poreux où nous prenons en considération le terme quadratique de Forchheimer dans les équations de l’énergie cinétique turbulente et le taux de dissipation. La résolution des équations obtenues a été effectuée numériquement par la méthode des volumes finis. Les résultats obtenus ont permis de mettre en évidence l’influence de l’épaisseur de la couche poreuse, la perméabilité ainsi que la conductivité thermique effective sur l’écoulement et le transfert thermique. Par ailleurs, il a été constaté que l’énergie cinétique turbulente est fortement influencée par la perméabilité et l’épaisseur de la couche poreuse. En outre un autre résultat substantiel a été étudié, il s’agit du rapport des conductivités thermiques car il a été constaté que ce rapport améliore notablement le transfert de chaleur sous certaines conditions.

Abstract: The morphology of the drying front at pore-scale was studied to gain a better understanding of the mass transport mechanisms that occur at pore-level. Therefore, a glass micromodel was built using a photolithographic technique. Micromodels can be defined as transparent networks of pores (pore bodies) and constrictions (pore throat) that capture the complexities of natural porous media. The micromodel was saturated with distilled water and frozen at −85 °C and then put into a laboratory lyophilizer maintained at −42 °C. Pore-level distribution of ice and vapor as the mass transport process advances were reported. Ice distribution in the bidimensional porous medium was slightly influenced by pore structure disorder. Two different sublimation regimes were also observed (fast front advance and slow front advance). Preliminary results show that the drying front for the slow front regimes scaling over time with an exponent of 0.577. [Copyright &y& Elsevier]

Abstract: In this paper the field equations of compressible oscillating flow in the regenerator of Pulse Tube Refrigerators (PTRs) are solved. To obtain an analytical solution, successive approximation technique is applied to continuity, momentum, gas and matrix energy equations and ideal gas equation of state. In this respect, the flow field variables are expanded to second-order unsteady terms. To introduce the influence of consecutive terms in the expansions, a comparative study is conducted on first unsteady, second steady and second unsteady terms. The proposed model presents a powerful analytical tool, applicable to oscillating flow analysis in porous media and rapid optimization of the pulse tube cycle. Results proved that expanding the terms to second-order ones can enhance the solution precision considerably. Friction factor and Nusselt number for different meshes are proposed based on the second-order analytical solution. [Copyright &y& Elsevier]

Abstract: A transient two-dimensional numerical model of combined heat and mass transfer in the adsorbent bed of a silica gel/water adsorption chiller is presented for a cylindrical bed with annular fins. The bed transient transport behaviors are discussed for all cycle phases. Complex flow patterns are found for isosteric heating and cooling phases due to the simultaneous occurrence of the adsorption and desorption processes. Furthermore, the effects of bed configurations such as fin spacing, bed height, and particle size on the performance of the system are examined. Results show that fins in general reduce the COP of the system; however, for a given total cooling power, the bed size can be reduced dramatically, when fins are employed at the cost of slightly lower COP. It is also shown that there is an optimum particle diameter associated with each bed configuration that maximizes the COP, TCP, and SCP of the system. [Copyright &y& Elsevier]

Abstract: A two-dimension porous medium model for a reciprocating active magnetic regenerator (AMR) of room temperature magnetic refrigeration has been developed. The thermal diffusion effect, heat flux boundary effect and variable fluid physical properties are considered in the model. In the paper, we compare the numerical results of the porous medium model with the experimental data and the calculation results of one-dimension Schumann model to validate our model. Our model can simulate the operation of the reciprocating AMR effectively. With the present model, the internal heat exchange between the two phases is numerically investigated. The two dimensional temperature distributions of the magnetic refrigerant and the refrigeration performance of AMR are obtained, and the influence of the heat flux boundary effect and the variable fluid properties on them is discussed. AMR can achieve a maximum refrigeration capacity of 293.7 W with a corresponding coefficient of performance (COP) of 5.4. [Copyright &y& Elsevier]

Abstract: Enhancement of heat transfer rate through porous fins is one of the common choices nowadays. As the energy equation is highly nonlinear, researchers never concentrated on analyzing porous fins analytically. In the present study, an effort has been devoted to develop an analytical model for determination of the performance and optimum dimensions of porous fins with consideration of different models of predictions. Every result has been presented in a comparative way so that the merit of the models adopting in the present work can easily be understood. The optimum design analysis of porous fins has also been carried out. The influences of all the dependent parameters on the performances and optimization conditions have been studied for the selection of a design criterion of porous fins in such applications where the requirement of heat dissipation is essentially high. [ABSTRACT FROM AUTHOR]

Abstract: Multiphase flow modelling is a major issue in the assessment of groundwater pollution. Three-phase flows are commonly governed by mathematical models that associate a pressure equation with two saturation equations. These equations involve a number of secondary variables that reflect the fluid behaviour in a porous medium. To improve the computational efficiency of multiphase flow simulators, several simplified reformulations of three-phase flow equations have been proposed. However, they require the construction of new secondary variables adapted to the reformulated flow equations. In this article, two different approaches are compared to quantify these variables. A numerical example is given for a typical fine sand. [ABSTRACT FROM AUTHOR]

In recent decades, problems related to the squeeze of fluid films in the presence of a porous medium draw attention of researchers and are the subject of many applied studies for industry and biomechanics. Our concerns in this paper are the numerical simulation of the viscous shear stresses effects on the fluid film characteristics between two discs with one porous. This study is based on the coupling, at the fluid film-porous disc interface, of the Darcy-Brinkman equations in the porous medium and the modified Reynolds equation describing the flow in the fluid film. The system of equations obtained is discretized by the means of finite differences method and solved numerically using the technique of Successive Over-Relaxation (SOR). The results show that the viscous shear effects increase the radial and the axial fluid film velocities as well as the squeeze film velocity but decrease the response time. Moreover, these effects are enlarged for smaller viscous shear parameter and for smaller fluid film thickness. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the instability of a viscoelastic fluid in a saturated porous medium heated from below and subjected to an horizontal through-flow. The Oldroyd-B constitutive equation is used to describe the viscoelastic behavior of diluted polymeric solutions. In the absence of the horizontal flow, the onset of convection can be characterized either by stationary or oscillatory instabilities. A temporal stability analysis is carried out in order to study the combined influence of the viscoelastic properties of the fluid and the main flow on the linear characteristics of these two types of instabilities. It is shown that the presence of the through-flow has a destabilizing effect and that it favors the emergence of mobile transverse rolls (R.T.), among an infinity of three-dimensional unstable modes. The thresholds for the appearance of these R.T., as well as their wavelengths and frequencies, are determined as functions of the dimensionless parameters of the problem. [Copyright &y& Elsevier]

Abstract: This article studies the water and heat transfer in the vadose zone of a carbonate formation during three hydrological cycles (August 2001–May 2004). The application of the time domain reflectometry (TDR) method to determine the volumetric water content of porous rocks has been widely investigated. The study of more than 285 monthly point measurements of the rock water content during three hydrological cycles, distributed throughout an abandoned underground quarry in Gironde, France, shows a permanently undersaturated limestone (between 35% and 50%). Three periods of maximum volumetric water content correspond to the occurrence of three effective rainfall events. The phase lag and amplitude damping of the hydraulic and thermal signals with depth can be modelled and explained by the hydraulic and thermal properties of the porous medium in the unsaturated zone. [Copyright &y& Elsevier]

Abstract: Widely used in food- and bio-engineering as a reference material, Agar-Agar gel is the focus of an experimental investigation concerning the electro-osmosis phenomenon. After presenting the experimental methods, one trial is discussed in detail. A fair reproducibility of results is obtained, and the averaged electro-osmotic permeability is provided. This value lies in the range generally measured on various kind of soils, even if Agar-Agar gel does not share any micro-structural characteristics with soils. To cite this article: F. Cherblanc et al., C. R. Mecanique 336 (2008). [Copyright &y& Elsevier]

Abstract: This paper presents an experimental study of the transport of suspended particles (SP) in a saturated porous medium, aimed at delineating the effects of pore structure on particle transport and deposition rate. Two porous media (silica gravel and glass beads) and silt SP were used. Breakthrough curves (BTCs) were well described by an analytical solution of the advective-dispersive equation with a first-order deposition kinetic. The recovery rate of suspended particles is higher in the glass beads even if the porosities are similar. This study shows the importance of pore distribution in transport processes of suspended particles. [Copyright &y& Elsevier]

Abstract: The operation behaviour of an active magnetic regenerator (AMR) with a wavy-structure, or a honeycomb-like regenerator bed was numerically investigated. The thermodynamic model was applied to a static regenerator and – in a generalized version – to a rotary type. The models take two-dimensional unsteady heat conduction in the magnetic material during the four basic processes of the AMR cycle into account. The numerical results were used to determine optimal arrangements of different magnetic materials in order to obtain larger temperature spans between both ends of the porous beds. Furthermore, a first study of magnetic flux lines in a porous rotary heat exchanger was performed. [Copyright &y& Elsevier]

Abstract: When the latent heat of a phase change material (PCM) with a lower melting point than ambient temperature was assessed according to the standard T-history method using a vertically oriented test tube, a temperature gradient occurred in the longitudinal direction of the tube due to natural convection. This led to a decrease in the accuracy of the latent heat of fusion measurement. In this study, the accuracy of the measurement with the original T-history method was improved without decreasing the test''s simplicity and convenience by setting the test tube horizontally. The heat transfer to the vapor-layer of the tube under volume change during melting was assumed to be negligible and the results were calculated using the two inflection points of temperature as the start and end of latent heat period. Under these assumptions, the results agree closely with other reference data. And, the new method proposed in this study showed a remarkable reduction in data scattering. [Copyright &y& Elsevier]

Abstract: An innovative hybrid hollow fiber membrane absorber and heat exchanger (HFMAE) made of both porous and nonporous fibers is proposed and studied via mathematical simulation. The porous fibers allow both heat and mass transfers between absorption solution phase and vapor phase, while the nonporous fibers allow heat transfer between absorption solution phase and cooling fluid phase only. The application of HFMAE on an ammonia–water absorption heat pump system as a solution-cooled absorber is analyzed and compared to a plate heat exchanger falling film type absorber (PHEFFA). The substantially higher amount of absorption obtained by the HFMAE is made possible by the vast mass transfer interfacial area per unit device volume provided. The most dominant factor affecting the absorption performance of the HFMAE is the absorption solution phase mass transfer coefficient. The application of HFMAE as the solution-cooled absorber and the water-cooled absorber in a typical ammonia–water absorption chiller allows the increase of COP by 14.8% and the reduction of the overall system exergy loss by 26.7%. [Copyright &y& Elsevier]

Abstract: The mechanical behavior of a partially saturated porous medium is addressed by means of a micro-to-macro reasoning. First, an estimate of the quadratic average over the solid phase of the equivalent shear strain is proposed. The latter is used in the framework of a nonlinear homogenization technique (‘modified secant’ method) in order to model the nonlinear poroelastic behavior in partially saturated conditions. The determination of the macroscopic strength criterion is then considered. Finally, the influence of membrane tension effects on strength is investigated. To cite this article: L. Dormieux et al., C. R. Mecanique 334 (2006). [Copyright &y& Elsevier]

Abstract: Objective. – The objective was to implement a predictive numerical model of periprosthetic healing supported by histomorphometric studies in canine implants. Material and methods. – The hypothesis was to couple cellular migration (osteoblasts) with growth factor diffusion in porous media to predict the periprosthetic tissue healing. The multiphasic macroscopic model involved solid and fluid fractions, cellular and growth factor concentrations. The axisymetric model of the implant permitted to predict the osteoblast migration (diffusion, convection, haptotaxis, chemiotaxis), the osteoid deposit, the interaction with growth factor diffusion and clinical conditions (drill hole). The numerical results have been compared with the in vivo histomorphometric data. Results. – The numerical model permitted to predict a generic healing pattern involving two main oscillations of the osseous solidity distribution. The analysis of solidity peak in terms of magnitude and location led to a classification into three main healings: homogenous with high mineralization, heterogeneous, homogeneous with low mineralization. Conclusion. – The numerical and histomorphometric correlations have been very satisfying in consideration of the complexity of mechanobiological phenomena. The model permitted to predict heterogeneous healing generally preceding the implant loosening. Now, the impact evaluation of clinical relevant parameters such as growth factor concentration and operative settings (drill hole) can be study to improve the long-term survival of the arthroplasty. [Copyright &y& Elsevier]

Abstract: We study in this paper the transport and deposition of suspended particles in saturated porous media. Some chromatographic short-pulse tests were performed in a laboratory column with a tracer and two types of suspended particles. A mathematical model was used to determine the hydrodispersive parameters and deposition rates from the breakthrough curves. The results show that the fitted parameters obtained vary with the flow rate and the characteristics of the suspended particles. We also observe, at high flow rates, that particles have a migration velocity higher than that of the conservative tracer. To cite this article: A. Benamar et al., C. R. Geoscience 337 (2005). [Copyright &y& Elsevier]

Copyright of Canadian Journal of Chemical Engineering is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Trapped-gas content in natural porous media, also called residual gas saturation (Sgr), corresponds to the imbibition end-point. To define the parameters controlling Sgr, two parameters were studied: the influence of rock characteristics (on 400 sandstone samples) and initial gas saturation (Sgi), on the basis of 60 experimental curves between Sgr and Sgi. Based on an extensive experimental database, this study establishes the dominant influence of microporosity on trapped gas saturation, and indirectly that of the contained clays. To cite this article: K. Suzanne, J. Billiotte, C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

A numerical simulation using Lees''s three-level scheme and a fixed grid was carried out to predict heat and mass transfer during the freezing of a porous humid matrix. The simulations predict local moisture content, temperature and weight loss of the foods throughout the freezing process. The model accommodates the effects of temperature dependent variables such as apparent specific heat, enthalpy, thermal conductivity, and water activity. The model was validated by experiments on a cellulose sponge. The results of the model showed good agreement with experimental data. [Copyright &y& Elsevier]

Pollution source characterization by the Partitioning Interwell Tracer Test method requires the assessment of the partitioning coefficient of the tracers with the pollutant. Experiments conducted on batch tests (static) and laboratory columns (dynamic) indicated a partitioning kinetics between the reactive tracer (4-methyl 2-pentanol) and the organic phase (trichlorethene); the partitioning coefficient decreases when the flow velocity through the porous medium increases. This partitioning kinetics has been confirmed by the interpretation of the tracer breakthrough curves with a first-order kinetic transfer model. To cite this article: M. Bohy et al., C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

The electrocatalytic hydrogenation (ECH) of phenol was carried out in aqueous media with a commercial Pd/Al2O3 (5% w/w) catalyst. A porous matrix of reticulated vitreous carbon (RVC) was used to study the porosity – stirring speed coupling (PSSC) effect on the phenol hydrogenation to form cyclohexanone and cyclohexanol. In accordance with the PSSC, the electrode can act as a fluidized bed electrode or as an agglomerated electrode. Fluidized bed electrodes develop for low porosity matrices (10–30 ppi, ppi = pores per inch) at high stirring speeds (>600 rpm), while agglomerated electrodes are obtained for high porosity matrices (60–100 ppi) with moderate stirring speeds under cathodic polarization. The distribution of the volume fraction of the particles and the agglomeration of the particles have been simulated by computational fluid dynamic (CFD) methods with FLUENT software. For the agglomerated electrode, the numerical simulations demonstrate the beneficial contribution of the cathodic polarization to the agglomeration process. However, at 650 rpm, for the fluidized bed electrode, the volume fraction of the particles in the RVC does not account for the distinction in the ECH efficiency between the 30 ppi matrix and the 100 ppi matrix. For a given amount of Pd/Al2O3 catalyst, it is observed that the ECH rates depend on the PSSC and increase in the following order: 100/650 < 30/650 < 100/200. [ABSTRACT FROM AUTHOR]

The aim of this Note is to quantify the change of characteristics of the media of an Excavated Damaged Zone (EDZ) affected by several fractures. For this, we consider Darcy flow through matrix blocks and fractures with permeability of order &epsiv;2δθ and 1 respectively. &epsiv; is the size of a typical porous block, δ representing the relative size of the fracture and θ is a parameter characterising the permeability ratio. We derive the global behavior from the limit as &epsiv; and δ tend to zero. The resulting homogenized equation is of dual-porosity type for θ=2, but it is a simple-porosity model with effective coefficients for θ>2, and there is no flow at the macroscopic level when 0<θ<2. To cite this article: B. Amaziane et al., C. R. Mecanique 332 (2004). [Copyright &y& Elsevier]

The modelling of heat transfer within materials with high porosity is complicated by evaporation-condensation phenomena. The aim of this work is to develop a model for apparent thermal conductivity in these products. The effective thermal conductivity of a porous food model (sponge) having 0–60% moisture contents and 0.59–0.94 porosity was measured by a line-source heat probe system in the range −35 to 25 °C. Two predictive models of the effective thermal conductivity of porous food were developed (Krischer and Maxwell models). The effective thermal conductivity predicted by Krischer model were in good agreement with the experimental data. Also, it was shown that the model including the effect of evaporation-condensation phenomena in addition to heat conduction was useful to predict the effective thermal conductivity of sponges. [Copyright &y& Elsevier]

The analytical solution developed by Dagan and Indelman (Water Resources Res. 35 (12) (1999) 3639–3647) for modelling the transport of a tracer in an infinite heterogeneous porous media in a dipole flow is extended by accounting for the presence of no flow finite boundaries. The results obtained are compared to those corresponding to the infinite domain, emphasizing the important influence of the boundaries on the elution at the pumping well and the effect of the medium''s heterogeneity. The analytical results are then compared to experimental data and provide good matching. To cite this article: J.-P. Carlier, P. Ackerer, C. R. Mecanique 331 (2003). [Copyright &y& Elsevier]

We propose a one-equation model for two-dimensional turbulent flow through porous media. The momentum equation is derived from the space averaging of Navier–Stokes equations, leading to the so-called Darcy–Forchheimer equations. In the turbulent kinetic energy transport equation, the production term is assumed to be proportional to the cube of velocity. The dissipation term is not estimated with a transport equation, it is explicitly given by a law involving turbulent kinetic energy and velocity. The model requires only four experimentally determined parameters. The local Nusselt number was correlated to local Reynolds number, and to local turbulence intensity. Good agreement between the simulated and the experimental local Nusselt number is obtained. [Copyright &y& Elsevier]

A numerical simulation by using a computational fluid dynamics (CFD) code is carried out to predict heat and mass transfer during vacuum cooling of porous foods on the basis of mathematical models of unsteady heat and mass transfer. The simulations allow the simultaneous prediction of temperature distribution, weight loss and moisture content of the meats at low saturation pressure throughout the chilling process. The simulations are also capable of accounting for the effects of the dependent variables such as pressure, temperature, density and water content, thermal shrinkage, and anisotropy of the food. The model is verified by vacuum cooling of cooked meats with cylindrical shape within an experimental vacuum cooler. A data file for pressure history was created from the experimental pressure values, which were applied in the simulations as the boundary condition of the surface temperature. [Copyright &y& Elsevier]

Bacterial mobility under unsaturated soils play an important role in the dispersal of pathogenic microorganisms and enhancing biorestoration of contaminated soil. Experiments were conducted to evaluate the effects of bacterial retention under unsaturated flow conditions in 5% and 10% bentonite–sand mixtures. Bacterial transport and retention was investigated under different rainfall events at 22°C and 4°C. Results indicated that bacterial accumulation was predominantly at the surface of the porous media and decreased with depth. Bacterial movement was also retarded relative to the chloride tracer in all fractions of the porous media. Heterogeneity of the porous media enhanced retention through filtration, specific surface area, and reduction in permeability. Recovery of the bacteria was influenced by the air–water interface with greater bacteria recovered at 4°C compared to 22°C. The colloidal filtration model described the distribution through the experimental columns. A linear relationship was observed between the filtration coefficient and the hydraulic conductivity from the different proportions of bentonite–sand. This correlation confirms that the colloidal filtration model can be used to determine the transport of bacteria through varying hydraulic conductivities of the porous media. Key words: porous media, hydraulic conductivity, retention, unsaturated flow, bacterial transport, filtration coefficient.La mobilité bactérienne sous les sols non saturés joue un rôle important dans la dispersion de microorganismes pathogènes et dans l'amélioration de la biorestauration des sols contaminés. Des expériences ont été effectuées afin d'évaluer les effets de la rétention bactérienne sous des conditions d'écoulement non saturé dans des mélanges de bentonite-sable à 5 % et 10 %. Le transport et la rétention des bactéries ont été étudiés lors de divers événements pluviaux à 22°C et à 4°C. Les résultats ont indiqué que l'accumulation bactérienne se faisait principalement à la surface du milieux poreux et qu'elle diminuait avec la profondeur. Le mouvement des bactéries a également été retardé par rapport au traceur de chlorure dans toutes les fractions du milieu poreux. L'hétérogénéité du milieu poreux a amélioré la rétention grâce à la filtration, la surface spécifique et la réduction de la perméabilité. La récupération des bactéries a été influencée par l'interface air-eau, la plus grande récupération de bactéries survenant à 4°C par rapport à 22°C. Le modèle de filtration colloïdale décrit la distribution au moyen des colonnes expérimentales. Une relation linéaire a été observée entre le coefficient de filtration et la conductivité hydraulique dans les différentes proportions du mélange bentonite-sable. Cette corrélation confirme que le modèle de filtration colloïdale peut être utilisé pour déterminer le transport des bactéries même lors des variations dans les conductivités hydrauliques du milieu poreux. Mots clés : milieu poreux, conductivité hydraulique, rétention, écoulement non saturé, transport des bactéries, coefficient de filtration.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The free convection, along a vertical flat plate embedded in a porous medium, can be described in terms of solutions to f‴+α+1/2ff″−αf′2=0, for all t∈(0,+∞). The purpose of this Note is to study the nonuniqueness of solutions to this problem, with the initial conditions, f(0)=a∈R and f′(0)∈{0,1}, where α∈(−1/3ff″−αf′2=0, for all t∈(0,+∞). The purpose of this Note is to study the nonuniqueness of solutions to this problem, with the initial conditions, f(0)=a∈R and f′(0)∈{0,1}, where α∈(−1/3,0). No assumption at infinity is imposed. We show that this problem has an infinite number of unbounded global solutions. Moreover, we prove that the first and the second derivative of solutions tend to 0 as t approaches infinity. To cite this article: M. Guedda, C. R. Mecanique 330 (2002) 279–283. [Copyright &y& Elsevier]