Résumé : Emilio Pons, declared that he is doing an excellent business. "'The required condition of the climate of Tampa for good cigars is said to be fully equal to that of Key West or Havana,' 'This has been proven by an actual and thorough test. Another advantage comes from the superior transportation facilities of the South Florida Railroad, which gets freight quickly to New York.'
(Funding) Digitized with funding from the Institute of Museum and Library Services as part of the Ephemeral Cities grant project.

Droits : All rights reserved. 2005.
C24-05722

Éditeur(s) : HAL CCSD
Résumé : This work is devoted to the theoritical research and to the numerical calculus of weak solutions (in the sens of generalized functions) for the non linear transport equation((∂u)/(∂t))(x,y,t)+a(x,y,t)((∂f(u))/(∂x))(x,y,t)+b(x,y,t)((∂g(u))/(∂y))(x,y,t)=0 pour t>0with the initial condition u(x,y,0)=u₀(x,y) where the functions {(x,y,t)→a(x,y,t)} and {(x,y,t)→b(x,y,t)} belong to L^{∞}(R²×R⁺) (but can be discontinuous), the functions f and g are smooth and monotonous, the function {(x,y)→u₀(x,y)} belongs to L^{∞}(R²). We recall the necessary notions on nonlinear generalized functions for introducing their tensorial product. The main results (to determine the weak solutions) are sufficient conditions so that, when a sum of généralized functions (like Heaviside or Dirac products) is associated with zero, each terms of the sum is equal to zero. Thanks to these theoretical results, we can solve the Riemann problem with the help of a solver written like tensorial product of Heaviside functions (or like a sum of tensorial product of Heaviside functions) in order to obtain the weak solutions. These weak solutions allow to develop two dimensional numerical Godunov type schemes. Then, numerical tests are performed which give a comparison between the results obtained by these 2D schemes and the ones of the splitting method. These tests prove that the 2D numerical schemes are as reliable as the ones obtained by splitting. They are also more simple in their expression. Moreover, a more detailed comparative study of the two types of numerical schemes show that the 2D schemes are far less expensive in the linear case as well as in the non linear case. They are stable for the L^{∞} norm, unlike the splitting schemes. At least some perspectives as well as an existence theorem of a strong solution "almost eveywhere" for linear hyberbolic systems are studied.
Nous nous intéressons à la recherche et au calcul numérique de solutions faibles (au sens des fonctions généralisées) de l'équation de transport non linéaire((∂u)/(∂t))(x,y,t)+a(x,y,t)((∂f(u))/(∂x))(x,y,t)+b(x,y,t)((∂g(u))/(∂y))(x,y,t)=0 pour t>0complétée de la condition initiale : u(x,y,0)=u₀(x,y) où les fonctions {(x,y,t)→a(x,y,t)} et {(x,y,t)→b(x,y,t)} appartiennent à L^{∞}(R²×R⁺) (mais peuvent être discontinues), les fonctions f et g sont lisses et monotones, la fonction {(x,y)→u₀(x,y)} appartient à L^{∞}(R²). Des rappels sur les fonctions généralisées nous permettent d'introduire leur produit tensoriel. Un des résultats clés (pour déterminer ultérieurement les solutions faibles cherchées) donne des conditions suffisantes pour que, lorsqu'une somme de fonctions généralisées (de type produit d'Heaviside ou de Dirac) est associée à 0, chacun des termes de la somme est nul. Grâce à ces résultats théoriques, on résout le problème de Riemann 2D à l'aide d'un solveur s'écrivant comme produit tensoriel de fonctions type Heaviside (ou comme somme de produit tensoriel de fonctions type Heaviside) afin d'obtenir les solutions faibles. Ces solutions faibles permettent la construction des schémas numériques de type Godunov 2D. Nous les validons par des test numériques comparant les résultats obtenus par ces schémas 2D et ceux de la méthode du splitting. Ces tests montrent que les schémas numériques 2D sont aussi fiables que ceux par splitting, alors qu'ils sont plus simples dans leur écriture. Une étude comparative plus complète entre les deux types de schémas numériques montre de plus que les schémas 2D sont nettement moins coûteux à la fois dans les cas linéaire et non linéaire et qu'ils sont stables pour la norme L^{∞}, contrairement aux schémas par splitting. Enfin des perspectives ainsi qu'un théoréme d'existence de solutions fortes "presque partout" pour des systèmes hyperboliques linéaires sont abordés.
https://hal.archives-ouvertes.fr/tel-01487366

Droits : info:eu-repo/semantics/OpenAccess
tel-01487366
https://hal.archives-ouvertes.fr/tel-01487366
https://hal.archives-ouvertes.fr/tel-01487366/document
https://hal.archives-ouvertes.fr/tel-01487366/file/th%C3%A8se_olivier_jouannelle_HAL.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A set of four reactive flow-through experiments at temperature T = 100 degrees C and total pressure P=12 MPa was performed in limestone reservoir samples. By using various ranging from 0.7 to 10 MPa, these experiments mimic mass transfers occurring (1) near the injection well, where the brine is almost saturated with CO2 (i.e. P-CO2 approximate to P), and (2) at increasing distances from the injection well, where the fluid displays lower values and higher divalent cation concentrations due rock dissolution along the fluid pathway. Results for P-CO2 = 10 MPa show non-uniform dissolution features associated with transport-controlled mass transfer, while reaction-controlled uniform dissolution is observed for P-CO2 = 2.5 MPa. The experiment with P-CO2 = 6 MPa allows investigating in detail the transition from transport-to reaction-controlled dissolution. Conversely, the experiment reproducing conditions far from the injection well (P-CO2 = 0.7 MPa), shows a decrease of porosity triggered by the precipitation of Mg-rich calcite. For all the dissolution experiments, the time-resolved porosity phi(t) can be modeled by a simple non-linear equation including parameters that characterise the dissolution regime triggered by the reactivity of the inlet fluid (measured by the Damkohler number, Da). Furthermore, all dissolution experiments display power scaling between permeability (k) and porosity (phi) with distinctly different scaling exponents characterising the reactivity of the fluid percolating the sample, independently from the decrease with time of the reactive surface area. It is shown also that dissolution at moderate positive values of Da seems the most efficient to increase permeability and promote a rapid spreading of the reaction front, while inducing minimal modification of the porosity in the vicinity of the CO2 injection well. These results can be used to parameterize the k-phi function for modeling the earliest dissolution processes occurring in the vicinity of the reaction front.
ISSN: 0009-2541

hal-00445277
https://hal.archives-ouvertes.fr/hal-00445277
DOI : 10.1016/j.chemgeo.2009.03.028

Éditeur(s) : HAL CCSD Elsevier
Résumé : The correct characterization of the effective reactive transport dynamics is an important issue for modeling reactive transport on the Darcy scale, specifically in situations in which reactions are localized, that is when different reactions occur in different portions of the porous medium. Under such conditions the conventional approach of homogenizing only the porous medium chemistry is not appropriate. We consider here reactive transport in a porous medium that is characterized by mass transfer between a mobile and a distribution of immobile regions. Chemical and physical heterogeneities are reflected by distributions of kinetic reaction rate constants and residence times in the immobile zones. We derive an effective reactive transport equation for the mobile solute that is characterized by non-local physical mass transfer and reaction terms. Specifically, chemical heterogeneity is upscaled in terms of a reactive memory function that integrates both chemical and physical heterogeneity. Mass transfer limitations due to physical heterogeneity yield effective kinetic rate coefficients that can be much smaller than the volumetric average of the local scale coefficients. These results help to explain and quantify the often reported discrepancy between observed field reaction rate constants and the ones obtained under well mixed laboratory conditions. Furthermore, these results indicate that transport under physical and chemical heterogeneity cannot be upscaled separately.
ISSN: 0169-7722

hal-00617674
https://hal.archives-ouvertes.fr/hal-00617674
DOI : 10.1016/j.jconhyd.2010.06.002

Éditeur(s) : HAL CCSD
Résumé : 18 pages
This article adresses questions on localization and microlocalization in the framework of the so called (C,E,P)-algebras of generalized functions. We give new results on nonlinear properties of the asymptotic singular spectrum in the multi-parameter case, a tool to describe the singularities of generalized solutions associated to problems which are classically ill-posed. Wa apply the theory to a transport equation with strongly irregular coefficients and initial data.
https://hal.univ-antilles.fr/hal-00761112

hal-00761112
https://hal.univ-antilles.fr/hal-00761112
https://hal.univ-antilles.fr/hal-00761112/document
https://hal.univ-antilles.fr/hal-00761112/file/DT2010-03_Devoue_al3.pdf

Éditeur(s) : Amer Geophysical Union
Résumé : Hydrographic (0-1000 dbar) and direct current measurements (0-600 dbar) along 165-degrees-E (20-degrees-S-10-degrees-N) between January 1984 and July 1991 are used to investigate the mean circulation and its relationships with the distributions of salinity and potential vorticity on isopycnal surfaces. Less well documented mean sections along 142-degrees-E and 137-degrees-E are used to complement the 165-degrees-E analysis. The Equatorial Undercurrent is centered on the equator at 165-degrees-E and on 0.5-degrees-N at 142-degrees-E. No variation in its transport (15.0 x 10(6) m3 s-1) is found between those longitudes. We find indication of the Equatorial Undercurrent at 137-degrees-E-0.75-degrees-N in the geostrophic field. The northern and southern Subsurface Countercurrents are clearly identified by extrema of eastward velocity at 165-degrees-E around 3-degrees-N and 3-degrees-S (250 dbar). No evidence of a southern Subsurface Countercurrent is found at 142-degrees-E. At 137-degrees-E the northern Subsurface Countercurrent is not characterized by a local extrema of eastward velocity: the North Equatorial Countercurrent seems to extend from the surface to 400 dbar with a southward shift of its core. Analysis of the seasonal variability at 165-degrees-E indicates that the Equatorial Undercurrent transport increases by a factor 2 between January (10.7 x 10(6) m3 s-1) and July (21.5 x 10(6) m3 s-1) and the Equatorial Intermediate Current transport is halved (6.3 x 10(6) m3 s-1 in January, 3.5 x 10(6) m3 s-1 in July). hi contrast, the transport of the Subsurface Countercurrents does not vary substantially between those two months. The meridional distributions of salinity and potential vorticity show that the axes of the main eastward currents are associated with strong meridional property gradients, not with property extrema. The eastward currents thus represent a barrier to the northward extension of the high salinity Tropical Water. Relatively weak meridional gradients of salinity and potential vorticity are observed in the westward directed South Equatorial Current and Equatorial Intermediate Current.
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 1993-12 , Vol. 98 , N. C12 , P. 22495-22520

Droits : 1993 by the American Geophysical Union.
http://archimer.ifremer.fr/doc/00192/30346/29190.pdf
DOI:10.1029/93JC02513
http://archimer.ifremer.fr/doc/00192/30346/

Éditeur(s) : Amer Geophysical Union
Résumé : The hydrological and geochemical properties of the waters constituting the Pacific Equatorial Undercurrent (EUC) determine the properties of the equatorial cold tongue. Understanding and quantifying the various EUC origins is therefore of prime importance. For this purpose, a high-resolution (1/4 degrees) interannual oceanic simulation was analyzed from the western tropical Pacific boundaries to 140 degrees W, using a Lagrangian framework. Waters from the Low-Latitude Western Boundary Currents (LLWBCs) transiting from Vitiaz Strait (the main contributor), from Solomon Strait, and via the Mindanao Current were identified as the principal sources to the EUC. Waters conveyed by the interior ocean off equator are negligible till 180 E. The LLWBCs' waters represent 87% of the EUC transport at 156 degrees E out of which the New Guinea Coastal Undercurrent (NGCU) is as large as 47%. The EUC meridional distribution suggests that the waters originating from Solomon Strait and Mindanao Current mostly remain in the hemisphere from which they originate. Contrastingly, Vitiaz Strait waters are found in both hemispheres. The vertical EUC distribution shows that the lower layer of the EUC is mainly composed of Vitiaz Strait waters. Finally, the source transport distributions were characterized, at their origin and within the EUC, as a function of density. These distributions showed that waters flowing through Vitiaz Strait at densities higher than those of the EUC (down to sigma(theta) = 27.2 kg m(-3)) undergo a diapycnal mixing and lighten during their journey to join the EUC. This lightening supports the suggestion that the NGCU is a major source for the EUC geochemical enrichment.
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2011-12 , Vol. 116 , N. C12044 , P. 16 p.

Droits : 2011 by the American Geophysical Union
http://archimer.ifremer.fr/doc/00060/17105/14621.pdf
DOI:10.1029/2011JC007477
http://archimer.ifremer.fr/doc/00060/17105/

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Mobile-immobile mass transfer is widely used to model non-Fickian dispersion in porous media. Nevertheless, the memory function, implemented in the sink/source term of the transport equation to characterize diffusion in the matrix (i.e., the immobile domain), is rarely measured directly. Therefore, the question can be posed as to whether the memory function is just a practical way of increasing the degrees of freedom for fitting tracer test breakthrough curves or whether it actually models the physics of tracer transport. In this paper we first present a technique to measure the memory function of aquifer samples and then compare the results with the memory function fitted from a set of field-scale tracer tests performed in the same aquifer. The memory function is computed by solving the matrix diffusion equation using a random walk approach. The properties that control diffusion (i.e., mobile-immobile interface and immobile domain cluster shapes, porosity, and tortuosity) are investigated by X-ray microtomography. Once the geometry of the matrix clusters is measured, the shape of the memory function is controlled by the value of the porosity at the percolation threshold and of the tortuosity of the diffusion path. These parameters can be evaluated from microtomographic images. The computed memory function compares well with the memory function deduced from the field-scale tracer tests. We conclude that for the reservoir rock studied here, the atypical non-Fickian dispersion measured from the tracer test is well explained by microscale diffusion processes in the immobile domain. A diffusion-controlled mobileimmobile mass transfer model therefore appears to be valid for this specific case.
ISSN: 0043-1397

insu-00373705
https://hal-insu.archives-ouvertes.fr/insu-00373705
https://hal-insu.archives-ouvertes.fr/insu-00373705/document
https://hal-insu.archives-ouvertes.fr/insu-00373705/file/Gouze_et_al-2008-Water_Resources_Research.pdf
DOI : 10.1029/2007WR006690

Éditeur(s) : Amer Geophysical Union
Résumé : In the Atlantic Ocean, the northward export of warm surface water is compensated by a southward flow of cold North Atlantic Deep Water (NADW). The NADW is transported southward along the American continental margin within the Deep Western Boundary Current (DWBC). Some tracer and float observations have shown that part of the DWBC water flows eastward along the equator. Here we present three meridional velocity sections which give an instantaneous image of the top-to-bottom zonal circulation along the equatorial Atlantic. They reveal the presence of Equatorial Deep Jets (EDJs) between 1 degrees 30'N and 1 degrees 30'S, alternating eastward-westward currents with short vertical scale, surrounded by columns of eastward currents (the Extra Equatorial Jets or EEJs) at 2 degreesN and 2 degreesS. In addition to direct velocity measurements, tracer distributions give indications of water-mass feeding of the EDJs and EEJs by the DWBC.
Geophysical Research Letters (0094-8276) (Amer Geophysical Union), 2001-03 , Vol. 28 , N. 5 , P. 819-822

Droits : 2001 AGU
http://archimer.ifremer.fr/doc/00000/10369/9567.pdf
http://archimer.ifremer.fr/doc/00000/10369/

Éditeur(s) : Gauthier-Villars
Résumé : The wind, temperature and current data collected during the joined French-USA FOCAL/SEQUAL programme carried in the equatorial Atlantic band in 1983 and 1984, allowed for the first time a simultaneous study of both the equatorial and coastal (5-degrees-N) upwellings along 4-degrees-W. At the equator, the decreases of both the surface temperature and the depth of the thermocline in boreal summer are correlated with the zonal component of the local windstress in the period band 1-2 months. This corresponds to the time required by the thermocline to lift up at 0-4-degrees-W in the presence of an easterly wind. The local wind cannot however explain the entire vertical variability of the thermal structure at 0-4-degrees-W. The correlation function shows in addition that the temperature there is highly correlated to the wind recorded at St Peter and St Paul Rocks (SPP) in the period band 0-2 months. This time scale is the one required by the Kelvin and Rossby waves to propagate along the equator through equatorial wave guide dynamics. The influence of these waves seems particularly important when considering the upward displacements of the thermocline both in February-March when the winds abruptly relax and in November-December when the wind at 0-4-degrees-W is southwesterly with no secondary negative maximum in the wind record at 1-degrees-N-29-degrees-W (SPP), contrary to the climatological wind field. The computation of the different terms of the heat equation applied to an homogeneous surface layer shows that the cooling is entirely due to vertical advection and eddy diffusion. The cooling would be more effective without the atmospheric heat flux and the horizontal advection of heat transported both by the South Equatorial Current at the surface and the southward current at the bottom of the mixed layer. At the coast, the amplitude and duration of the upwellings are not constant all along the coast: in boreal summer, they are maximum east of the two capes (Palmas and Three Pointes) while in winter the strength of the cooling is maximum in the east of Cape Palmas and then decreases eastward. The meridional slope of the thermocline off the coast concerns a distance which is much larger than the internal Rossby radius of deformation and is coherent with the latitudinal extension and intensity of the Guinea current both in summer and winter. In addition to this geostrophic adjustment, the upward tilt of the thermocline in summer is enhanced by the intensification of the component of the wind parallel to the coast. The application of a simple linear model forced with an eastward wind at that time explains the surface maximum cooling at the coast and the current distribution in both vertical and meridional directions. The two maxima of the zonal component of the Guinea current, in summer (main one) and in winter are in phase with the intensity of the vertical component of the windcurl. The application of the Sverdrup equations shows that the current speeds computed, for both seasons, are of the same order of magnitude as the speeds observed.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1991 , Vol. 14 , N. 3 , P. 223-240

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00101/21252/18865.pdf
http://archimer.ifremer.fr/doc/00101/21252/

Éditeur(s) : HAL CCSD
Résumé : I propose a self contained research paper. I hope it adds some news ideas and results to the …xed point theory in the framework of generalized functions algebras, with application to the Cauchy-Lipschitz problem in a generalized formulation including strongly irregular cases. This leads to the transport equation with distributions as coe¢ cients we wish to treat later.
https://hal.univ-antilles.fr/hal-01231272

Droits : info:eu-repo/semantics/OpenAccess
hal-01231272
https://hal.univ-antilles.fr/hal-01231272
https://hal.univ-antilles.fr/hal-01231272/document
https://hal.univ-antilles.fr/hal-01231272/file/Fixed%20points%20in%20generalized%20algebras.pdf

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
By means of convenient regularization for an ill posed Cauchy problem, we define an associated generalized problem and discuss the conditions for the solvability of it. To illustrate this, starting from the semilinear unidirectional wave equation with data given on a characteristic curve, we show existence and uniqueness of the solution
ISSN: 0973-5348

hal-01529519
https://hal.univ-antilles.fr/hal-01529519
DOI : 10.1051/mmnp/201611207

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
We derive a general formulation of the time domain random walk (TDRW) approach to model the hydrodynamic transport of inert solutes in complex geometries and heterogeneous media. We demonstrate its formal equivalence with the discretized advection-dispersion equation and show that the TDRW is equivalent to a continuous time random walk (CTRW) characterized by space-dependent transition times and transition probabilities. The transition times are exponentially distributed. We discuss the implementation of different concentration boundary conditions and initial conditions as well as the occurrence of numerical dispersion. Furthermore, we propose an extension of the TDRW scheme to account for mobile-immobile multirate mass transfer. Finally, the proposed TDRW scheme is validated by comparison to analytical solutions for spatially homogeneous and heterogeneous transport scenarios.
ISSN: 0043-1397

hal-01356319
https://hal.archives-ouvertes.fr/hal-01356319
DOI : 10.1002/2015WR018511

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
We develop and implement a new method to take into account the impact of waves into the 3-D circulation model SYMPHONIE (Marsaleix et al., 2008, 2009a), following the simplified equations of Bennis et al. (2011) which use glm2z-RANS theory (Ardhuin et al., 2008b). These adiabatic equations are completed by additional parameterizations of wave breaking, bottom friction and wave-enhanced vertical mixing, making the forcing valid from the surf zone through to the open ocean. The wave forcing is performed by wave generation and propagation models WAVEWATCH III® (Tolman, 2008, 2009; Ardhuin et al., 2010) and SWAN (Booij et al., 1999). The model is tested and compared with other models for a plane beach test case, previously tested by Haas and Warner (2009) and Uchiyama et al. (2010). A comparison is also made with the laboratory measurements of Haller et al. (2002) of a barred beach with channels. Results fit with previous simulations performed by other models and with available observational data. Finally, a realistic case of energetic waves travelling over a coast of the Gulf of Lion (in the northwest of the Mediterranean Sea) for which currents are available at different depths as well as an accurate bathymetric database of the 0-10 m depth range, is then simulated. A grid nesting approach is used to account for the different forcings acting at different spatial scales. The simulation coupling the effects of waves and currents is successful to reproduce the powerful northward littoral drift in the 0-15 m depth zone. More precisely, two distinct cases are identified: when waves have a normal angle of incidence with the coast, they are responsible for complex circulation cells and rip currents in the surf zone, and when they travel obliquely, they generate a northward littoral drift. These features are more complicated than in the test cases, due to the complex bathymetry and the consideration of wind and non-stationary processes. Wave impacts in the inner shelf are less visible since wind and regional circulation seem to be the predominant forcings. Besides, a discrepancy between model and observations is noted at that scale, possibly linked to an underestimation of the wind stress. Lastly, this three-dimensional method allows a good representation of vertical current profiles and permits to calculate the shear stress associated with wave and current. Future work will focus on the combination with a sediment transport model.
ISSN: 1812-0806

hal-00766548
https://hal.archives-ouvertes.fr/hal-00766548
https://hal.archives-ouvertes.fr/hal-00766548/document
https://hal.archives-ouvertes.fr/hal-00766548/file/os-8-657-2012.pdf
DOI : 10.5194/osd-8-2417-2011

Éditeur(s) : HAL CCSD Coastal Education and Research Foundation
Résumé : The present work concerns cuspate spits: slightly symmetrical geomorphic features growing along the shoreline in shallow waters. We develop a new formulation for the dynamics of cuspate spits. Our approach relies on classical paradigms such as a conservation law to the shoreface scale and an explicit formula for alongshore sediment transport. We derive a non-linear diffusion equation and a fully explicit solution for the growth of cuspate spits. From this general expression, we found interesting applications to quantify shoreline dynamics in the presence of cuspate spits. In particular, we point out a simple method for the datation of a cuspate spit given a limited number of input parameters. Furthermore, we develop a method to quantify the mean alongshore diffusivity along a shoreline perturbed by well-defined cuspate spits of known sizes. Finally, we introduce a formal relationship between the geometric characteristics (amplitude, length) of cuspate spits, which reproduce the self-similarity of these geomorphic features.
ISSN: 0749-0208

hal-01234952
https://hal.archives-ouvertes.fr/hal-01234952
DOI : 10.2112/SI70-009.1

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
We show how to introduce the Value at Risk (VaR) concept in the analysis of the adaptation of the shape of a soft bed to a flow knowing the Probability Density Function (PDF) of the responses of the shape to flow perturbations (bed receptivity). Our aim is to quantify our confidence on simulation scenarios by an available morphodynamic model for the shape. The approach permits to perform this task at low complexity as it does not require any sampling of the bed receptivity parameter space. The paper goes beyond stationarity for the variability of the bed receptivity by linking its dynamics to the bottom morphodynamics through an original transport equation for the local bed receptivity standard deviation. The approach has been applied to the analysis of bed morphodynamics based on minimization principles. The results show the importance of including uncertainty information during the coupling and not only eventually through simple margins on the results.
ISSN: 0045-7930

hal-01054937
https://hal.archives-ouvertes.fr/hal-01054937
https://hal.archives-ouvertes.fr/hal-01054937/document
https://hal.archives-ouvertes.fr/hal-01054937/file/paper_var_litto.pdf
DOI : 10.1016/j.compfluid.2013.10.021

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Numerical programs for simulating flow and reactive transport in porous media is essential for predicting reservoir properties related to CO2 sequestration performance, subsurface storage and risk assessment. In this paper we solve the Navier Stokes' equation using finite difference method, on a simulated porous rock structure, to study the velocity distribution of fluid flowing through it under a constant pressure gradient. A reactive solute carried through the fluid is allowed to interact with the minerals in the rock. This chemical reaction dissolves the mineral which changes the rock structure thus affecting its flow properties. These changes of flow properties are studied with variation in reactive solute concentration and pressure field. The different mechanisms of dissolution responsible for the variation of flow properties for the different parameters is predicted. Before the onset of homogeneous dissolution, variation in porosity follows a power-law behaviour with change in permeability when the latter is scaled by the concentration of the reactive species. The simulation results are compared with available experimental data and found to give a reasonable match.
ISSN: 0022-1694

hal-00757760
https://hal.archives-ouvertes.fr/hal-00757760
DOI : 10.1016/j.jhydrol.2012.05.024

Éditeur(s) : HAL CCSD Humana Press
Résumé : International audience
The sodium-proton exchanger 1 (NHE-1) is a membrane transporter that exchanges Na(+) for H(+) ion across the membrane of eukaryotic cells. It is cooperatively activated by intracellular protons, and this allosteric regulation is modulated by the biophysical properties of the plasma membrane and related lipid environment. Consequently, NHE-1 is a mechanosensitive transporter that responds to osmotic pressure, and changes in membrane composition. The purpose of this study was to develop the relationship between membrane surface tension, and the allosteric balance of a mechanosensitive transporter such as NHE-1. In eukaryotes, the asymmetric composition of membrane leaflets results in a difference in surface tensions that is involved in the creation of a reservoir of intracellular vesicles and membrane buds contributing to buffer mechanical constraints. Therefore, we took this phenomenon into account in this study and developed a set of relations between the mean surface tension, membrane asymmetry, fluid phase endocytosis and the allosteric equilibrium constant of the transporter. We then used the experimental data published on the effects of osmotic pressure and membrane modification on the NHE-1 allosteric constant to fit these equations. We show here that NHE-1 mechanosensitivity is more based on its high sensitivity towards the asymmetry between the bilayer leaflets compared to mean global membrane tension. This compliance to membrane asymmetry is physiologically relevant as with their slower transport rates than ion channels, transporters cannot respond as high pressure-high conductance fast-gating emergency valves.
ISSN: 1085-9195

inserm-00871709
http://www.hal.inserm.fr/inserm-00871709
http://www.hal.inserm.fr/inserm-00871709/document
http://www.hal.inserm.fr/inserm-00871709/file/art_3A10.1007_2Fs12013-012-9340-7.pdf
DOI : 10.1007/s12013-012-9340-7

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In this paper we solve the Navier Stokes’ equation using finite difference method, on a simulated porous rock structure in 2-D, to study the velocity distribution of fluid flowing through it under a constant pressure gradient. A reactive solute carried through the fluid is allowed to interact with the minerals in the rock. Depending on the rock composition, both dissolution and precipitation reactions may occur. However precipitation occurs only through the cations that are released in the solution due to dissolution. These combined dissolution–precipitation reactions change the porosity, permeability and pore geometry of the sedimentary rock. We study the temporal changes of these properties as functions of Peclet number, concentration of the reactive solute and ratio of Damkholer numbers of dissolution to precipitation. The final flow property is decided by a combination of these parameters.
ISSN: 0022-1694

hal-01115291
https://hal.archives-ouvertes.fr/hal-01115291
DOI : 10.1016/j.jhydrol.2014.10.019

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
To evaluate the performance of downhole and surface geophysical monitoring methods, a series of shallow gas injection-monitoring experiments has been performed in a coastal saline aquifer at Maguelone, France. The recorded data include pressure measurements with a Westbay multilevel completion and CO2 saturation at an observation well derived from electrical resistivity with a modified Waxman-Smits (MWS) model. In this work, the aim is to develop a simulation model capturing the gas transport behavior and consistent with field data. For this purpose, the simulation of the CO2 injection experiment is carried out with two conceptual models, a homogeneous model and a heterogeneous model treated with multiple realization Monte Carlo simulations. Numerical simulator TOUGH2 with the equation of state module EOS7C is used for the simulations. Comparison of the model results with field data suggests that the pressure responses are captured with relatively good accuracy. Similarly, the model also provides an overall reasonable agreement and correct order of magnitude for predicted gas saturation values. However, as the heterogeneity pattern in the field data remains largely unknown, the model predictions can only be used to capture the mean behavior as well as to provide insights into how heterogeneity can influence the system behavior, by means of sensitivity analyses of the influence of heterogeneities on individual realizations.
ISSN: 1750-5836

hal-01467240
https://hal.archives-ouvertes.fr/hal-01467240
DOI : 10.1016/j.ijggc.2016.09.006