Backscatter in stratified turbulence
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Date
2016-11
Authors
Khani, Sina
Waite, Michael L
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
In this paper, kinetic and potential energy transfers around a spectral test fil ter scale in direct numerical simulations of decaying stratified turbulence are
studied in both physical and spectral domains. It is shown that while the
domain-averaged effective subgrid scale energy transfer in physical space is a
net downscale cascade, it is actually a combination of large values of downscale
and upscale transfer, i.e. forward- and backscatter, in which the forward scatter
is slightly dominant. Our results suggest that spectral backscatter in stratified
turbulence depends on the buoyancy Reynolds number Reb and the filtering
scale ∆test. When the test filter scale ∆test is around the dissipation scale Ld,
transfer spectra show spectral backscatter from sub-filter to intermediate scales,
as reported elsewhere. However, we find that this spectral backscatter is due
to viscous effects at vertical scales around the test filter. It is also shown that
there is a non-local energy transfer from scales larger than the buoyancy scale
Lb to small scales.The effective turbulent Prandtl number spectra demonstrate
that the assumption P rt ≈ 1 is reasonable for the local energy transfer.
Description
The final publication is available at Elsevier via http://dx.doi.org/https://doi.org/10.1016/j.euromechflu.2016.06.012. © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Keywords
Stratified turbulence, Direct numerical simulations, up- and downscale energy transfer