Small-Scale Isotropy and Ramp-Cliff Structures in Scalar Turbulence

Dhawal Buaria, Matthew P. Clay, Katepalli R. Sreenivasan, P. K. Yeung

Research output: Contribution to journalArticlepeer-review

Abstract

Passive scalars advected by three-dimensional Navier-Stokes turbulence exhibit a fundamental anomaly in odd-order moments because of the characteristic ramp-cliff structures, violating small-scale isotropy. We use data from direct numerical simulations with grid resolution of up to 81923 at high Péclet numbers to understand this anomaly as the scalar diffusivity, D, diminishes, or as the Schmidt number, Sc=ν/D, increases; here ν is the kinematic viscosity of the fluid. The microscale Reynolds number varies from 140 to 650 and Sc varies from 1 to 512. A simple model for the ramp-cliff structures is developed and shown to characterize the scalar derivative statistics very well. It accurately captures how the small-scale isotropy is restored in the large-Sc limit, and additionally suggests a possible correction to the Batchelor length scale as the relevant smallest scale in the scalar field.

Original languageEnglish (US)
Article number034504
JournalPhysical Review Letters
Volume126
Issue number3
DOIs
StatePublished - Jan 22 2021

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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