Buoyancy-driven Exchange Flow through Double Openings with Having Multi Flow Patterns.

This paper describes an experimental study of the phenomenon of buoyancy-driven exchange (countercurrent) flow through openings in a horizontal partition. A density-driven exchange flow was obtained by using brine above the partition and fresh water below the partition. In the first part of the study, flow measurements were made with a single opening, for opening ratios L/D in the range 0.01 to 10.0, where L and D are the length of the opening (in the direction normal to the partition) and the diameter of the opening, respectively. Four different flow regimes are identified as L/D is increased through this range. As a result of the competition between two of these regimes, the exchange flow rate versus L/D relation exhibits a peak. The exchange flow rate was found, for all practical purposes, to be independent of viscosity, enabling a universal correlation between Froude number (dimensionless exchange flow rate) and L/D. The second part of the study was an experimental investigation of the same phenomenon, but with two openings in the horizontal partition. Two openings were observed to give rise to three different flow configurations involving both one-way and countercurrent flows within the openings.

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Effect of the opening aspect ratio on a buoyant pulsating exchange flow through a circular ceiling opening in a horizontal partition

Heat Transfer-Asian Research ◽

10.1002/htj.21023 ◽

2012 ◽

Vol 41 (8) ◽

pp. 666-680 ◽

Cited By ~ 4

Author(s):

B. Gera ◽

P.K. Sharma ◽

R.K. Singh

Keyword(s):

Aspect Ratio ◽

Exchange Flow ◽

Flow Through ◽

Horizontal Partition

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Maximal two-layer exchange over a sill and through the combination of a sill and contraction with barotropic flow

Journal of Fluid Mechanics ◽

10.1017/s002211208600246x ◽

1986 ◽

Vol 164 ◽

pp. 53-76 ◽

Cited By ~ 241

Author(s):

D. M. Farmer ◽

L. Armi

Keyword(s):

Surface Layer ◽

Reverse Flow ◽

Single Layer ◽

The Other ◽

Exchange Flow ◽

Strait Of Gibraltar ◽

Exchange Flows ◽

Barotropic Flow ◽

Flow Through ◽

Layer Flow

The analysis of two-layer exchange flow through contractions with a barotropic component treated by Armi & Farmer (1986) is extended to include exchange flows over sills and through a combination of a sill and contraction. It is shown that exchange over a sill is fundamentally different from exchange through a contraction. Control at the sill crest acts primarily through the deeper layer into which the sill projects and only indirectly controls the surface layer. This asymmetry in the control results in asymmetrical flows. The interface depth above the crest is not one half the total depth, as assumed in other studies by analogy with flow through contractions, but is somewhat deeper; the maximal exchange rate is less than for flow through a contraction of equal depth. When both a sill and a contraction are present, the contraction influences control at the sill crest only if it lies between the sill and the source of denser water. The response to barotropic flow is also asymmetrical: the transition to single-layer flow occurs at much lower speeds for a barotropic component in one direction than the other.Results of the analysis are applied to exchange flow through the Strait of Gibraltar, which includes both a sill and a contraction. It is shown that maximal exchange conditions apply throughout part of the tidal cycle, and observations illustrate several of the analytical predictions for barotropic flows, including the formation of fronts, single-layer flow, submaximal exchange and reverse flow.

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