Instantaneous cascade dynamics in turbulent flows*

The fluctuations of interscale energy transfers. interspace energy transfers, rates of energy change in time, pressure effects and turbulence dissipation, but also their interactions, are studied in Direct Numerical Simulations of statistically stationary periodic turbulence. We use the Kármán-Howarth-Monin-Hill equation and solenoidal/irrotational decompositions as well as a decomposition of the intescale energy transfer rate into a term dominated by local inhomogeneity/spatial intermittency and a term dominated by eddy correlations. The results reveal a picture of fluctuating energy and energy exchanges and dissipation which is very different from the average cascade picture provided by the Kolmogorov theory of statistically stationary homogeneous turbulence.