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Random shearing by zonal flows and transport reduction

  • Author(s): Kim, EJ
  • Diamond, PH
  • et al.

Published Web Location

https://doi.org/10.1063/1.1808455Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Public License
Abstract

The physics of random shearing by zonal flows and the consequent reduction of scalar field transport are studied. In contrast to mean shear flows, zonal flows have a finite autocorrelation time and can exhibit complex spatial structure. A random zonal flow with a finite correlation time τZFdecorrelates two nearby fluid elements less efficiently than a mean shear flow does. The decorrelation time is τD=(τη/τZFΩ2rms)1/2(τnis the turbulent scattering time, and Ωrmsis the rms shear), leading to larger scalar field amplitude with a slightly different scaling (∝τD/Ωrms), as compared to the case of coherent shearing. In the strong shear limit, the flux scales as ∝Ωrms-1. © 2004 American Institute of Physics.

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