Intermittency in the isotropic component of helical and nonhelical turbulent flows

Abstract

We analyze the isotropic component of turbulent flows spanning a broad range or Reynolds numbers. The aim is to identify scaling laws and their Reynolds number dependence in flows under different mechanical forcings. To this end, we applied an SO(3) decomposition to data stemming from direct numerical simulations with spatial resolutions ranging from 643 to 10243 grid points, and studied the scaling of high order moments of the velocity field. The study was carried out for two different flows obtained forcing the system with a Taylor-Green vortex or the Arn'old-Beltrami-Childress flow. Our results indicate that helicity has no significant impact on the scaling exponents as obtained from the generalized structure functions. Intermittency effects increase with the Reynolds number in the range of parameters studied, and in some cases are larger than what can be expected from several models of intermittency in the literature. The observed dependence of intermittency with the Reynolds number decreases if extended self-similarity is used to estimate the exponents. © 2010 The American Physical Society.