J. Phys. IV France 11 (2001) Pr6-57-Pr6-64
Additional transport by oscillatory buoyancy driven convection in diffusion experimentsV. Botton1, J.-P. Garandet2, T. Alboussière3 and P. Lehmann1
1 EPM-Madylam, ENSHMG, BP. 95, 38402 Saint-Martin-d'Hères, France
2 Commissariat à l'Énergie Atomique, DTA/CEREM/DEM/SPCM/LSP, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 9, France
3 Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, U.K.
A model for the transverse g-jitters induced transport in binary diffusion experiments is presented. The flow is supposed parallel and oscillating at a single frequency supposed high compared to the solute lateral diffusion time scale. This model applies to long aspect ratio experiments. A time-averaged effective diffusivity approach allows us to recover several recently published results and to provide a better understandaing of the underlying physics. In the case of a given fully established velocity profile, the variation of the effective diffusion coefficient is such that (Deff-D)/D follows an ω-2 or an ω-7/2 law respectively for low and high frequency compared to the momentum lateral diffusion time scale. The transport by this type of flow is shown to be hardly significant in typical impurity diffusion experiment in microgravity.
© EDP Sciences 2001