Turbulent heat transport regimes in a channel

In this paper we focus on the turbulent transport of a scalar through a channel. The scalar flux and the corresponding scalar concentration gradient along the channel allow us to define a Nusselt number and a Grashof number. While the relation between the large-scale velocity field and the input energy rate show perfect inertial (turbulent) behavior, three different regimes can be distinguished, with different scalings between Nusselt and Grashof numbers.