Scale-Energy Fluxes in Wall-Turbulent Flows

According to the Kolmogorov theory, the most important feature of high Reynolds number turbulent flows is the energy transfer from large to small scales. This energy cascade is believed to universally occur in a certain interval of scales, known as inertial range. This phenomenology has been shown to occur in a wide range of flows but not in wall-turbulence where a reverse cascade in the near-wall region is observed [1]. In order to analyse this new scenario, in the present work a study of a generalized Komogorov equation is performed. The results reveal an energy fluxes loop in the space of scales where the reverse cascade plays a central role. At the base of this phenomena it is found the anisotropic energy injection due to the action of the turbulent structures involved in the near-wall cycle. The data used for the analysis are obtained with a pseudo-spectral code in a channel at Re-tau = 550. The computational domain is 8 pi h x 2h x 4 pi h with a resolution in the homogeneous directions of Delta x(+) - 13.5 and Delta z(+) - 6.7.