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This video presents experimental Rayleigh-Bénard convection, at high Rayleigh number, using shadowgraphy technique. The liquid used is a Fluorocarbon and is heated from below and cooled from the top to generate a roll of convection. Shadowgraphy permit to see the variation of the optical index inside a media. It is particularly useful for convection since the variation of density or temperature impact the value of the optical index. This is the reason why we can see the plumes pretty contrasted as they carry the heat. The set-up consists in a direct shadowgraphy in diverging light. The cell is illuminated by a punctual monochromatic light source which is far enough from the cell, that the light is almost parallel. The shadowgraph pattern is captured on a ground glass diffuser, and recorded with the camera. Associated publication : “Turbulent transition in Rayleigh-Bénard convection with Fluoro-carbon“ Credit : Lucas Méthivier, Julien Salort, Francesca C
