Anomalous scaling of passive scalars in rotating flows

TL;DR

This paper investigates how passive scalars behave in rotating turbulent flows, revealing anisotropic scaling laws, reduced intermittency, and confirming theoretical predictions through direct numerical simulations.

Contribution

It provides new insights into the anisotropic scaling and intermittency of passive scalars in rotating turbulence, supported by detailed numerical analysis.

Findings

Passive scalar exhibits more anisotropy than velocity field.

Passive scalar power spectrum follows a ~k_perp^{-3/2} law.

Intermittency decreases more in velocity than in passive scalar under rotation.

Abstract

We present results of direct numerical simulations of passive scalar advection and diffusion in turbulent rotating flows. Scaling laws and the development of anisotropy are studied in spectral space, and in real space using an axisymmetric decomposition of velocity and passive scalar structure functions. The passive scalar is more anisotropic than the velocity field, and its power spectrum follows a spectral law consistent with $\sim k_\perp^{-3/2}$. This scaling is explained with phenomenological arguments that consider the effect of rotation. Intermittency is characterized using scaling exponents and probability density functions of velocity and passive scalar increments. In the presence of rotation, intermittency in the velocity field decreases more noticeably than in the passive scalar. The scaling exponents show good agreement with Kraichnan's prediction for passive scalar intermittency in two-dimensions, after correcting for the observed scaling of the second order exponent.