On the decrease of intermittency in decaying rotating turbulence

TL;DR

This study investigates how intermittency decreases in decaying rotating turbulence by analyzing velocity structure functions, revealing changes in scaling exponents over time and the influence of rotation.

Contribution

It provides detailed measurements of structure function exponents in rotating turbulence, highlighting the evolution of intermittency and deviations from non-rotating turbulence.

Findings

The second-order exponent $$ increases during decay.

Higher-order exponents deviate from non-rotating turbulence at larger times.

Intermittency decreases but does not vanish entirely in rotating turbulence.

Abstract

The scaling of the longitudinal velocity structure functions, $S_q(r) = < | \delta u (r) |^q > \sim r^{\zeta_q}$, is analyzed up to order $q=8$ in a decaying rotating turbulence experiment from a large Particle Image Velocimetry (PIV) dataset. The exponent of the second-order structure function, $\zeta_2$, increases throughout the self-similar decay regime, up to the Ekman time scale. The normalized higher-order exponents, $\zeta_q / \zeta_2$, are close to those of the intermittent non-rotating case at small times, but show a marked departure at larger times, on a time scale $\Omega^{-1}$ ($\Omega$ is the rotation rate), although a strictly non-intermittent linear law $\zeta_q / \zeta_2 = q/2$ is not reached.