Document Type

Article

Publication Date

11-2017

Publication Title

PHYSICAL REVIEW FLUIDS 2

ISSN

2469-990X

Volume

2

Issue

11

DOI

https://doi.org/10.1103/PhysRevFluids.2.113801

Abstract

Eddy energy transport in rotating two-dimensional turbulence is investigated using numerical simulation. Stochastic forcing is used to generate an inhomogeneous field of turbulence and the time-mean energy profile is diagnosed. An advective-diffusive model for the transport is fit to the simulation data by requiring the model to accurately predict the observed time-mean energy distribution. Isotropic harmonic diffusion of energy is found to be an accurate model in the case of uniform, solid-body background rotation (the f plane), with a diffusivity that scales reasonably well with a mixing-length law. kappa alpha Vl where V and l are characteristic eddy velocity and length scales. Passive tracer dynamics are added and it is found that the energy diffusivity is 75% of the tracer diffusivity. The addition of a differential background rotation with constant vorticity gradient beta leads to significant changes to the energy transport. The eddies generate and interact with a mean flow that advects the eddy energy. Mean advection plus anisotropic diffusion (with reduced diffusivity in the direction of the background vorticity gradient) is moderately accurate for flows with scale separation between the eddies and mean flow, but anisotropic diffusion becomes a much less accurate model of the transport when scale separation breaks down. Finally, it is observed that the time-mean eddy energy does not look like the actual eddy energy distribution at any instant of time. In the future, stochastic models of the eddy energy transport may prove more useful than models of the mean transport for predicting realistic eddy energy distributions.

Comments

©2017 American Physical Society

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