The ultimate state of thermal convection
  The ultimate regime of thermal convection, the so called Kraichnan regime (R. H. Kraichnan, Phys. Fluids 5, 1374 (1962)), hitherto has been elusive. Here, numerical evidence for that regime is presented by performing simulations of the bulk of turbulence only, eliminating the thermal and kinetic boundary layers and replacing them by periodic boundary conditions. 
Detlef Lohse and Federico Toschi