Exact Energy Transfers in Turbulence
Quantifying heat transport in turbulent convection remains a challenge. The two competing models of heat transport predict that heat transport scales as $(dT)^{3/2}$ (ultimate regime scaling) or $(dT)^{1.3}$ (classical scaling), where dT is the temperature difference between the top and bottom plates that confine the fluids. Our synergetic and comparative study indicates the latter scaling. Using extreme numerical simulations, we demonstrate that the positive and negative energy fluxes in turbulent convection are nearly equal; however, the positive flux prevails over the negative flux, with the difference scaling as $(dT)^{-0.20}$, which leads to a $(dT)^{1.3}$ scaling. The above robust and universal properties are attributed to the confining thermal plates. The features differ significantly from those of periodic convection, which is often related to the ultimate regime.