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


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 8192^{3} 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
Issue number3
StatePublished - Jan 22 2021

ASJC Scopus subject areas

  • General Physics and Astronomy


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