Confirmation of Faraday's explanation of bunkering in vibrated granular beds

Convection, Heaping, and Cracking in Vertically Vibrated Granular Slurries

“…Similar features were documented with clay suspensions [9], which illustrate one possible response of a fluidparticle system. Interstitial fluid (gas or liquid) is known to lead to convection in granular systems by a mechanism first postulated by Faraday, in which the surrounding fluid is drawn towards the center of a convecting domain, dragging particles along with it, as a vibrating plate accelerates downwards [1,[10][11][12]. In our experiments with thin layers of wet granular material, surface tension at the air-water interface precludes some aspects of this mechanism.…”