The internal structure of forced fountains
File(s)
Published version
Author(s)
Huang, Jingzi
Burridge, Henry C
van Reeuwijk, Maarten
Type
Journal Article
Abstract
We study the mixing processes inside a forced fountain using data from direct
numerical simulation. The outer boundary of the fountain with the ambient is a
turbulent/non-turbulent interface. Inside the fountain, two internal
boundaries, both turbulent/turbulent interfaces, are identified: 1) the
classical boundary between upflow and downflow which is composed of the loci of
points of zero mean vertical velocity; and 2) the streamline that separates the
mean flow emitted by the source from the entrained fluid from the ambient (the
separatrix). We show that entrainment due to turbulent fluxes across the
internal boundary is at least as important as that by the mean flow. However,
entrainment by the turbulence behaves substantively differently from that by
the mean flow and cannot be modelled using the same assumptions. This presents
a challenge for existing models of turbulent fountains and other environmental
flows that evolve inside turbulent environments.
numerical simulation. The outer boundary of the fountain with the ambient is a
turbulent/non-turbulent interface. Inside the fountain, two internal
boundaries, both turbulent/turbulent interfaces, are identified: 1) the
classical boundary between upflow and downflow which is composed of the loci of
points of zero mean vertical velocity; and 2) the streamline that separates the
mean flow emitted by the source from the entrained fluid from the ambient (the
separatrix). We show that entrainment due to turbulent fluxes across the
internal boundary is at least as important as that by the mean flow. However,
entrainment by the turbulence behaves substantively differently from that by
the mean flow and cannot be modelled using the same assumptions. This presents
a challenge for existing models of turbulent fountains and other environmental
flows that evolve inside turbulent environments.
Date Issued
2023-04-24
Date Acceptance
2023-02-24
Citation
Journal of Fluid Mechanics, 2023, 961, pp.1-29
ISSN
0022-1120
Publisher
Cambridge University Press
Start Page
1
End Page
29
Journal / Book Title
Journal of Fluid Mechanics
Volume
961
Copyright Statement
© The Author(s), 2023. Published by Cambridge University Press. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
License URL
Identifier
http://arxiv.org/abs/2301.09618v1
Subjects
physics.flu-dyn
physics.flu-dyn
Publication Status
Published
Date Publish Online
2023-04-24