ABSTRACT
So far, there is a reasonable qualitative agreement between the results of experiments conducted on dilute granular media and the predictions of kinetic models inspired from the hard sphere gas theory (For an extensive review, see Savage, 1993). However, experiments conducted on dense rapid granular flows lead to drastically different results, results which appear to lie beyond the domain of validity of standard hydrodynamic descriptions. The reason is likely that for dense media, there are long-lasting contacts between grains, and that the basis hypothesis of binary collisions does not hold. Contrary to dilute granular gases, for which the transport of momentum proceeds from ballistic flights and interparticle collisions, the most efficient channel to transport momentum and energy is supported by the continuous paths of contacts in densely-packed granular media.
