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Abstract: The onset of Soret-driven convection in a shallow porous horizontal layer filled with a binary mixture and submitted to a vertical heat flux on the two horizontal walls is investigated. We study the species separation between the two vertical ends of the cell, which appears for low values of the Rayleigh number and for positive separation ratio. An analytical solution is performed and the separation is expressed in terms of thermal Rayleigh number, Lewis number, separation ratio and aspect ratio of the cell. These analytical results are corroborated by direct non-linear numerical simulations. Then, the results are compared with those obtained in a differentially heated vertical cavity. [Copyright &y& Elsevier]

Abstract: Microgravity experiments and molecular dynamics simulations have been performed to study thermodiffusion of ternary mixtures composed of methane, n-butane and n-dodecane in petroleum reservoirs conditions. The simulations showed in both cases that methane and n-butane tend to migrate towards the hot side while n-dodecane tends to migrate towards the cold side. Some of the experimental results showed the same trend but with much larger amplitudes. Finally, a simulation of an idealized fluid column composed of one of the ternary mixture emphasizes that thermodiffusion can have a large impact on the vertical distribution of the components in a petroleum reservoir. [Copyright &y& Elsevier]

Abstract: The aim of this article is to present briefly a summary of the state of art in theoretical, experimental and numerical approaches in thermodiffusion. The concepts and equations giving the mass flux of constituents in binary, ternary and multicomponent mixtures are presented. [Copyright &y& Elsevier]