title: Intermittency and scale-dependent statistics in fully developed turbulence.
abstract: Fully developed homogeneous isotropic turbulent fields, computed by direct numerical simulation, are compared to divergence-free random fields having the same energy spectrum and either the same helicity spectrum as that of the turbulent data, or vanishing helicity. We show that the scale-dependent velocity flatness quantifies the spatial variability of the energy spectrum. The flatness exhibits a substantial increase at small scales for the turbulent field, but remains constant for the random fields. A diagnostic, the scale-dependent helicity, is proposed to quantify the geometrical statistics of the flow, which shows that only the turbulent flow is intermittent. Finally, statistical scale-dependent analyses of both Eulerian and Lagrangian accelerations confirm the inherently different dynamics of turbulent and random flows.
authors.affiliation: Department of Computational Science and Engineering, Nagoya University, Nagoya 464-8603, Japan.
authors.forename: Katsunori
authors.initials: K
authors.lastname: Yoshimatsu
authors.forename: Naoya
authors.initials: N
authors.lastname: Okamoto
authors.forename: Kai
authors.initials: K
authors.lastname: Schneider
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kaneda
authors.forename: Marie
authors.initials: M
authors.lastname: Farge