Resonance enhanced turbulent transport

TL;DR

This paper investigates how oscillatory shear flows influence turbulent transport, revealing that resonance effects can enhance diffusion and that such flows may accelerate turbulence rather than suppress it.

Contribution

It provides a numerical analysis showing the dual role of shear flows in suppressing or enhancing turbulence through resonance mechanisms.

Findings

Resonances can enhance turbulent transport.

Oscillatory shear flows may accelerate turbulence.

Turbulence amplitude scales depend on shear parameters.

Abstract

The effect of oscillatory shear flows on turbulent transport of passive scalar fields is studied by numerical computations based on the results provided by E. Kim [\emph{Physics of Plasmas}, {\bf 13}, 022308, 2006]. Turbulent diffusion is found to depend crucially on the competition between suppression due to shearing and enhancement due to resonances, depending on the characteristic time and length scales of shear flow and turbulence. Enhancements in transport occur for turbulence with finite memory time either due to Doppler and parametric resonances. Scalings of turbulence amplitude and transport are provided in different parameter spaces. The results suggest that oscillatory shear flows are not only less efficient in regulating turbulence, but also can enhance the value of turbulent diffusion, accelerating turbulent transport.