Worm's characteristics in 'classical' and 'non-equilibrium' turbulence*

The characteristics of the intense vorticity structures or 'worms' are analysed in direct numerical simulations (DNS) of isotropic turbulence in i) 'classical' and ii) 'non-equilibrium' turbulence, where the two types of turbulence/simulations are achieved by manipulating the forcing applied at the large scale motions.

The simulations cover a range of Taylor based Reynolds numbers between 90 ≤ Re_λ ≤ 399, and k_maxη ≈ 2.0, where k_max is the maximum resolved wavenumber and η is the Kolmogorov's micro-scale, and the 'worms' characteristics analysed comprise the a) vortex core radius, b) vorticity profiles, c) tangential velocity and d) filament lengths. While for 'classical' turbulence the mean vortex core radius is approximately ivs>/η ≈ 4 - 5, the radius are observed to increase slightly in 'non-equilibrium' turbulence, when the power of the input forcing is suddenly decreased. More results will be discussed during the presentation.