Rotating helical turbulence. II. Intermittency, scale invariance, and structures

Abstract

We study the intermittency properties of the energy and helicity cascades in two 15363 direct numerical simulations of helical rotating turbulence. Symmetric and antisymmetric velocity increments are examined, as well as probability density functions of the velocity field and of the helicity density. It is found that the direct cascade of energy to small scales is scale invariant and nonintermittent, whereas the direct cascade of helicity is highly intermittent. Furthermore, the study of structure functions of different orders allows us to identify a recovery of isotropy of strong events at very small scales in the flow. Finally, we observe the juxtaposition in space of strong laminar and persistent helical columns next to time-varying vortex tangles, the former being associated with the self-similarity of energy and the latter with the intermittency of helicity.