We investigate the self-similar evolution of the transient energy spectrum which precedes the establishment of the Kolmogorov spectrum in homogeneous isotropic turbulence in three dimensions using the EDQNM closure model. The transient evolution exhibits self-similarity of the second kind and has a non-trivial dynamical scaling exponent which results in the transient spectrum having a scaling which is steeper than the Kolmogorov $k^{-5/3}$ spectrum. Attempts to detect a similar phenomenon in DNS data are inconclusive owing to the limited range of scales available.

6 pages, 4 figures. Euromech colloquium 512 "Small scale turbulence and related gradient statistics", Accademia delle Scienze, Turin, Italy (26-29 Oct 2009) Version 2 corrects some typos and contains additional simulations and analysis on forced turbulence