Abstract

Quantifying diapycnal mixing in stably stratified turbulence is fundamental to the understanding and modeling of geophysical flows. Data of diapycnal mixing from direct numerical simulations of homogeneous stratified turbulence and from grid turbulence experiments, are analyzed to investigate the scaling of the diapycnal diffusivity. In these homogeneous flows the instantaneous diapycnal diffusivity is given exactly by Kd= ∈ρ/ (∂ ρ /∂z)2where ∈ρ is the dissipation rate of density fluctuations, and ∂ ρ /∂z is the mean density gradient. The diffusivity Kd may be expressed in terms of the large-scale properties of the turbulence as K d = γLE2 /TL, where L E is the Ellison overturning length-scale, TL is the turbulence decay timescale, and γ is half the mechanical to scalar time-scale ratio. Our results show that LE and TL can explain most of the variations in Kd over a wide range of shear and stratification strengths while γ remains approximately constant. © Copyright 2010 by the American Geophysical Union.

Department(s)

Civil, Architectural and Environmental Engineering

Publication Status

Free Access

International Standard Serial Number (ISSN)

1944-8007; 0094-8276

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

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© 2025 Wiley; American Geophysical Union, All rights reserved.

Creative Commons Licensing

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Publication Date

01 Jan 2010

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