On few aspects of the dynamics of granular matter

Abstract

This paper, in French, describes a series of completely different behaviours of the mechanics of granular matter, which are obtained experimentally using periodic forcing at different amplitude, frequency and orientation. It starts with the problem of granular dissipative gas which has been investigated in micro-gravity ; it is found that such a gas exists only at very low density ; it is shown also that clustering occurs at larger density. Is this a phase transition ? The problem of dissipative Sinai billiard is then investigated briefly ; is it ergodic ? An experiment on propagation of acoustic wave is studied, with peculiar attention paid to scattering and diffusion that occurs when acoustic wavelength is comparable to the grain size. A third experiment demonstrates that bulk convection can be induced by slow (quasi static) horizontal forcing ; this flow is related to the quasi static rheology of granular matter, but looks rather like convection occurring under "dynamic vibration". A fourth experiment describes pure inertial effect, making the sand behaving as a perfect (non viscous) fluid ; in particular, it is shown that a static swell 9that does not propagate) is enforced at the interface between liquid and sand by strong periodic horizontal forcing . Pacs # : 5.40 ; 45.70 ; 62.20 ; 83.70.Fn