54 research outputs found
Two-dimensional hydrodynamic lattice-gas simulations of binary immiscible and ternary amphiphilic fluid flow through porous media
The behaviour of two dimensional binary and ternary amphiphilic fluids under
flow conditions is investigated using a hydrodynamic lattice gas model. After
the validation of the model in simple cases (Poiseuille flow, Darcy's law for
single component fluids), attention is focussed on the properties of binary
immiscible fluids in porous media. An extension of Darcy's law which explicitly
admits a viscous coupling between the fluids is verified, and evidence of
capillary effects are described. The influence of a third component, namely
surfactant, is studied in the same context. Invasion simulations have also been
performed. The effect of the applied force on the invasion process is reported.
As the forcing level increases, the invasion process becomes faster and the
residual oil saturation decreases. The introduction of surfactant in the
invading phase during imbibition produces new phenomena, including
emulsification and micellisation. At very low fluid forcing levels, this leads
to the production of a low-resistance gel, which then slows down the progress
of the invading fluid. At long times (beyond the water percolation threshold),
the concentration of remaining oil within the porous medium is lowered by the
action of surfactant, thus enhancing oil recovery. On the other hand, the
introduction of surfactant in the invading phase during drainage simulations
slows down the invasion process -- the invading fluid takes a more tortuous
path to invade the porous medium -- and reduces the oil recovery (the residual
oil saturation increases).Comment: 48 pages, 26 figures. Phys. Rev. E (in press
Three dimensional hysdrodynamic lattice-gas simulations of binary immiscible and ternary amphiphilic flow through porous media
We report the results of a study of multiphase flow in porous media. A
Darcy's law for steady multiphase flow was investigated for both binary and
ternary amphiphilic flow. Linear flux-forcing relationships satisfying Onsager
reciprocity were shown to be a good approximation of the simulation data. The
dependence of the relative permeability coefficients on water saturation was
investigated and showed good qualitative agreement with experimental data.
Non-steady state invasion flows were investigated, with particular interest in
the asymptotic residual oil saturation. The addition of surfactant to the
invasive fluid was shown to significantly reduce the residual oil saturation.Comment: To appear in Phys. Rev.
Transtorno autÃstico e doença celÃaca : sem evidências de associação
Objective: To evaluate the possible association between celiac disease (CD) and/or gluten sensitivity (GS) and autism spectrum disorder
(ASD). Methods: Occurrences of CD were determined in a group of children and adolescents affected by ASD and, conversely, occurrences
of ASD were assessed in a group of biopsy-proven celiac patients. To detect the possible existence of GS, the levels of antigliadin antibodies in ASD patients were assessed and compared with the levels in a group of non-celiac children. Results: The prevalence of CD or GS in
ASD patients was not greater than in groups originating from the same geographical area. Similarly the prevalence of ASD was not greater
than in a group of biopsy-proven CD patients. Conclusion: No statistically demonstrable association was found between CD or GS and ASD.
Consequently, routine screening for CD or GS in all patients with ASD is, at this moment, neither justifed nor cost-effective. ___________________________________________________________________________________ RESUMOObjetivo: Avaliar a possÃvel associação entre doença celÃaca (DC) e/ou sensibilidade ao glúten (SG) e transtorno do espectro autista (TEA).
Métodos: Ocorrências de DC foram determinadas em um grupo de crianças e adolescentes afetados pelo TEA e a ocorrência d TEA foi
avaliada em um grupo de pacientes com DC comprovada por biópsia. Para detectar a possÃvel existência de SG, foram determinados nÃveis
de anticorpos antigliadina em pacientes com TEA e comparados ao grupo de crianças sem a doença celÃaca. Resultados: A prevalência de
DC ou SG não foi maior no grupo de pacientes com TEA quando comparada a grupos de indivÃduos originários da mesma região geográfca.
De modo similar, a prevalência do TEA não foi maior ao ser comparada ao grupo de pacientes com DC. Conclusão: Não houve associação
estatisticamente demonstrável entre DC ou SG e TEA. Consequentemente, não são justifcáveis, no momento, exames de rotina para detecção de DC ou SG em pacientes com TEA
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Characterization, Reconstruction and Transport Properties of Vosges Sandstones Caractérisation, reconstruction et propriétés de transport des grès des Vosges
A thorough study of Vosges sandstone samples is presented in this work. First, the geometry of these porous media is analyzed using serial thin sections. Then, random numerical samples are reconstructed according to the measured statistical geometrical parameters. Finally, the macroscopic transport properties are determined from the numerical solutions in the reconstructed samples of the local equations governing the corresponding transport phenomena and compared to available experimental data. Mercury intrusion in the simulated media is modelled and pore size distribution results are compared with those obtained from serial tomography. Dans cet article, nous présentons une étude approfondie d'échantillons de grès des Vosges. La géométrie de ces milieux est analysée en utilisant des coupes sériées. Puis des échantillons aléatoires sont reconstruits en accord avec les propriétés géométriques statistiques mesurées. Enfin, les propriétés macroscopiques de transport sont déduites des solutions numériques dans les échantillons reconstruits des équations locales qui régissent les transports correspondants, et elles sont comparées aux mesures disponibles. La pénétration de mercure dans les échantillons est modélisée et les résultats relatifs aux distributions de pores sont comparés à ceux obtenus sur les coupes sériées
Characterization, Reconstruction and Transport Properties of Vosges Sandstones
A thorough study of Vosges sandstone samples is presented in this work. First, the geometry of these porous media is analyzed using serial thin sections. Then, random numerical samples are reconstructed according to the measured statistical geometrical parameters. Finally, the macroscopic transport properties are determined from the numerical solutions in the reconstructed samples of the local equations governing the corresponding transport phenomena and compared to available experimental data. Mercury intrusion in the simulated media is modelled and pore size distribution results are compared with those obtained from serial tomography
Characterization, Reconstruction and Transport Properties of Vosges Sandstones
International audienceA thorough study of Vosges sandstone samples is presented in this work. First, the geometry of these porous media is analyzed using serial thin sections. Then, random numerical samples are reconstructed according to the measured statistical geometrical parameters. Finally, the macroscopic transport properties are determined from the numerical solutions in the reconstructed samples of the local equations governing the corresponding transport phenomena and compared to available experimental data. Mercury intrusion in the simulated media is modelled and pore size distribution results are compared with those obtained from serial tomography
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