Rayleigh-bénard convection

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Abstract
This paper presents a physicist's approach to Rayleigh-Bénard convection widely illustrated with experimental results. The basis of the mechanism of the instability is simply presented with physical reasons for the existence of a critical threshold. A detailed examination of the spatial organization is made with discussion of ordered and disordered structures. Furthermore it is shown that the measurements of the local velocity give a good quantitative description of the convective state. A complete parallel between the Rayleigh-Bénard convection near onset and a critical phenomenon is given in the framework of a mean field approach, including both spatial as well as temporal effects. Non-Boussinesq convection is presented as symmetry breaking, changing the second order transition into a (partially) first order transition. The last section is devoted to the ever present but still not completely understood question of the dynamics of the convective pattern; the importance of the existence and motion of defects is pointed out. Finally, a tentative and provisional survey is made of two open questions: the wavenumber selection and the approach of turbulence in large aspect ratio cells.

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