Hydraulic control of flow in a multi-passage system connecting two basins

When a fluid stream in a conduit splits in order to pass around an obstruction, it is possible that one branch will be critically controlled while the other remains not so. This is apparently the situation in Pacific Ocean abyssal circulation, where most of the northward flow of Antarctic bottom wat...

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Bibliographic Details
Published in:Journal of fluid mechanics 2022-06, Vol.940, Article A8
Main Authors: Tan, S., Pratt, L.J., Voet, G., Cusack, J.M., Helfrich, K.R., Alford, M.H., Girton, J.B., Carter, G.S.
Format: Article
Language:English
Subjects:
Abyssal circulation
Abyssal zone
Bottom friction
Bottom water
Channel flow
Connecting
Energy dissipation
Flow control
Fluid mechanics
Hydraulic control
Hydraulics
JFM Papers
Mathematical models
Numerical models
Partitioning
Potential vorticity
Rotation
Steady state
Theories
Topography
Upstream
Volume transport
Vorticity
Water circulation
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Summary:When a fluid stream in a conduit splits in order to pass around an obstruction, it is possible that one branch will be critically controlled while the other remains not so. This is apparently the situation in Pacific Ocean abyssal circulation, where most of the northward flow of Antarctic bottom water passes through the Samoan Passage, where it is hydraulically controlled, while the remainder is diverted around the Manihiki Plateau and is not controlled. These observations raise a number of questions concerning the dynamics necessary to support such a regime in the steady state, the nature of upstream influence and the usefulness of rotating hydraulic theory to predict the partitioning of volume transport between the two paths, which assumes the controlled branch is inviscid. Through the use of a theory for constant potential vorticity flow and accompanying numerical model, we show that a steady-state regime similar to what is observed is dynamically possible provided that sufficient bottom friction is present in the uncontrolled branch. In this case, the upstream influence that typically exists for rotating channel flow is transformed into influence into how the flow is partitioned. As a result, the partitioning of volume flux can still be reasonably well predicted with an inviscid theory that exploits the lack of upstream influence.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2022.212