Abstract

New insight for inferring diapycnal diffusivity in stably stratified turbulent flows is obtained based on physical scaling arguments and tested using high-resolution direct numerical simulation data. It is shown that the irreversible diapycnal diffusivity can be decomposed into a diapycnal length scale that represents an inner scale of turbulence and a diapycnal velocity scale. Furthermore, it is shown that the diapycnal length scale and velocity scale can be related to the measurable Ellison length scale (LE) that represents outer scale of turbulence and vertical turbulent velocity scale (w ′) through a turbulent Froude number scaling analysis. The turbulent Froude number is defined as F r = ϵ / N k, where ϵ is the rate of dissipation of turbulent kinetic energy, N is the buoyancy frequency, and k is the turbulent kinetic energy. The scaling analysis suggests that the diapycnal diffusivity K ρ ∼ w ′ L E in the weakly stratified regime (Fr >1) and K ρ ∼ (w ′ L E) x F r for the strongly stratified regime (Fr < 1).

Department(s)

Civil, Architectural and Environmental Engineering

Publication Status

Available Access

Comments

National Science Foundation, Grant OCE-2149047

International Standard Serial Number (ISSN)

1089-7666; 1070-6631

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2025 American Institute of Physics, All rights reserved.

Publication Date

01 Sep 2022

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