The present study is devoted to the description of the energy fluxes from production to dissipation in the augmented space (3-dimensional space of scales plus wall-distance) of wall-turbulent flows. As already shown in Cimarelli et al. (2010), an interesting behavior of the energy fluxes comes out from this analysis consisting of spiral-like paths in the combined physical/scale space where the controversial reverse energy cascade plays a central role. The observed behaviour conflicts with the classical notion of the Richardson/Kolmogorov energy cascade and may have strong repercussions on both theoretical and modeling approaches to wall-turbulence. Two dynamical processes are identified as driving mechanisms for the fluxes, one in the near wall region and a second one further away from the wall. The former, stronger one is related to the dynamics involved in the near-wall cycle. The second suggests an outer self-sustaining mechanism. Here we extend these results to larger Reynolds number using LES data of a turbulent channel flow at Reτ = 970 confirming the presence of an outer regeneration cycle which seems to be composed by systems of attached eddies.
Assessment of the turbulent energy paths from the origin to dissipation in wall-turbulence / Cimarelli, A.; De Angelis, E.; Casciola, C. M.. - 318:2(2011), pp. 022007-022014. [10.1088/1742-6596/318/2/022007]