Isotropization at small scales of rotating helically driven turbulence

P.D. MININNI; D. ROSENBERG; A. POUQUET

JOURNAL OF FLUID MECHANICS

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2012 vol. 699 p. 263 - 279

0022-1120

We present numerical evidence of how three-dimensionalization occurs at small scale in rotating turbulence with Beltrami (ABC) forcing, creating helical flow. The Zeman scale at which the inertial and eddy turn-over times are equal is more than one order of magnitude larger than the dissipation scale, with the relevant domains (large-scale inverse cascade of energy, dual regime in the direct cascade of energy and helicity , and dissipation) each moderately resolved. These results stem from the analysis of a large direct numerical simulation on a grid of points, with Rossby and Reynolds numbers, respectively, equal to and . At scales smaller than the forcing, a helical wave-modulated inertial law for the energy and helicity spectra is followed beyond by Kolmogorov spectra for and . Looking at the two-dimensional slow manifold, we also show that the helicity spectrum breaks down at , a clear sign of recovery of three-dimensionality in the small scales.