Several aspects of the Bénard instability are approached in this work. After having described the principle of the experiments by underlining the role of the two driving forces of instability, namely surface tension and buoyancy, we show first of all, for configurations of large horizontal extension, various types of convective patterns, all made of 2D pavements of convective cells (hexagonal, square). The narrow similarity between these 2D patterns and the 2D polycristals (presence of grains, dislocations, grain boundaries) is shown. Structural order may be studied with the traditional tools (optical or mathematical Fourier transform, radial and angular correlation functions). A comparison between this (partial) disorder and mathematical models built independently of the physical phenomenon is established (minimal spanning tree, Aboav-Weaire, Lewis laws...) The agreement is surprisingly good. A study of the structural disorder can be presented as a function of Marangoni number until reaching spatio-temporal chaos. Dimensions of the attractors are calculated

The area of study belongs to the higher building of the base of Small Kabylie. It consists of several tectono-lithological units affected by a metamorphism épizonale to mésozonale of low pressure and high temperature. This last estimated at P=4-5 Kbar and T=650-700°C is underlined by the presence of the veins of leucozones and the myrmékite thus near to the field of partial fusion. The structural draft shows the superposition of schisto-sandy units épizonales on units of higher rank. This area is overcome in its Western and Eastern part by formations of Oligo-Miocène-Kabyle. The study of the syn-schistous deformation highlights an extensive component at vergency is and of the linéations of stretching of direction E - W (D1) with a virgation towards the NNE. This deformation induces the shape in arc marked by plans of schistosity and foliation resulting from the deformation (D2) due to the accommodation of the total overlapping of the building of Beni-Ferguène towards the NW. Alpine and eo-alpine post-schistous deformations of lower (Pt), at vergency East and South, are highlighted.

Dans cet article le modèle de Darcy et l’approximation de Boussinesq sont utilisés pour étudier la convection naturelle dans un milieu poreux saturé par un fluide binaire. La géométrie considérée est celle d’une cavité partiellement chauffée par le bas et refroidie par le haut. Les forces solutales résultent de l’imposition de concentrations constantes imposées sur les surfaces horizontales de la cavité. L’existence de solutions multiples pour ce type de configuration est démontrée numériquement.