Comment on: ”Convective flow of granular masses

2014 It is demonstrated using Faraday exprimental results and interpretations that air should not play a major cast in the experimental data published by Laroche et al.. This is also supported by other more recent studies. J. Phys. France 51 (1990) 697-700 15 AVRIL 1990, Classification Physics Abstracts 46.10-47.20F-05.60 The experimental results reported in this paper are really beautiful and no doubt they will help understanding the convective flow regim and the very peculiar shapes and geometries that a sand pile can take when it is vertically shaken. However, it seems to us that the interprotation given in this paper emphasizes the effect of air too much, so that these phenomena are still misunderstood from our point of view. Furthermore, one can test qualitatively and quantitatively a correct interprétation of these results, when it will be achieved, by comparing directly its theoretical predictions to the other data already published [1-6]. Such a global interpretation is not yet possible: the published experimental behaviors are quite différent from one another, although they have been obtained using slightly different expérimental set-ups [1-6]; this tends to prove that a vibrated sand pile is sensitive to small perturbations, such as a change in the boundary conditions [7] or a small transverse vibration [7]. In [7], we have not only tried to discuss such possibilities in a general fashion, but also to check the relevance of already existing theories [2 3] to interpret these phenomena [1 6]. We want to discuss here only the relevance of an existing air flow, which is claimed by Laroche et al. to create the convective pattern. We do not deny the existence of this air flow, but only contest that it is the motor of the pattern under these expérimental conditions, (which are not too Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphys:01990005108069700