PLUME MODEL FOR THE BOUNDARY-LAYER DYNAMICS IN HARD TURBULENCE

''Hard turbulence'' has come to be associated with several features of high-Rayleigh-number Boussinesq convection: thermal plumes, intermitt ency, nonclassical Nu-Ra scaling (Nu is-proportional-to Ra2/7 ), large -scale circulation, and the strongly sheared thermal boundary layers t hat result. In this paper, we make use of one of these features, the p lumes, to offer an explanation of recent measurements of ''waves'' pro pagating on the boundary layers. The measured ''dispersion relation'' is reproduced here by a scaling theory incorporating the drag force of buoyant plumes and the interaction of these plumes with the boundary layers.