Fractal scaling of the turbulence interface in gravity currents
File(s)
Accepted version
Author(s)
Krug, D
Holzner, M
Marusic, I
Van Reeuwijk, M
Type
Journal Article
Abstract
It was previously observed by Krug et al. (J. Fluid Mech., vol. 765, 2015, pp. 303–324) that the surface area 𝐴𝜂 of the turbulent/non-turbulent interface (TNTI) in gravity currents decreases with increasing stratification, significantly reducing the entrainment rate. Here, we consider the multiscale properties of this effect using direct numerical simulations of temporal gravity currents with different gradient Richardson numbers 𝑅𝑖𝑔 . Our results indicate that the reduction of 𝐴𝜂 is caused by a decrease of the fractal scaling exponent 𝛽 , while the scaling range remains largely unaffected. We further find that convolutions of the TNTI are characterized by different length scales in the streamwise and wall-normal directions, namely the integral scale ℎ and the shear scale 𝑙𝑆𝑘=𝑘1/2/𝑆 (formed using the mean shear 𝑆 and the turbulent kinetic energy 𝑘 ) respectively. By recognizing that the anisotropy implied by the different scaling relations increases with increasing 𝑅𝑖𝑔 , we are able to model the 𝑅𝑖𝑔 dependence of 𝛽 in good agreement with the data.
Date Issued
2017-06-10
Date Acceptance
2017-04-11
Citation
Journal of Fluid Mechanics, 2017, 820 (1), pp.R3-1-R3-12
ISSN
0022-1120
Publisher
Cambridge University Press
Start Page
R3-1
End Page
R3-12
Journal / Book Title
Journal of Fluid Mechanics
Volume
820
Issue
1
Copyright Statement
© Cambridge University Press 2017. This paper has been accepted for publication and will appear in a revised form, subsequent to peer-review and/or editorial input by Cambridge University Press.
Identifier
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/fractal-scaling-of-the-turbulence-interface-in-gravity-currents/1141049D31AACC2583EF3DC8E28DEF58
Subjects
Science & Technology
Technology
Physical Sciences
Mechanics
Physics, Fluids & Plasmas
Physics
geophysical and geological flows
gravity currents
stratified turbulence
ENTRAINMENT
Fluids & Plasmas
01 Mathematical Sciences
09 Engineering
Publication Status
Published
Article Number
R3
Date Publish Online
2017-05-09