Hydraulic Control of Sill Flow with Bottom Friction

Pratt, Larry J.

doi:10.1175/1520-0485(1986)016<1970:hcosfw>2.0.co;2

Cited by 87 publications

(72 citation statements)

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“…C d Ã is usually on the order of 10 −3 ; 10 Pratt noted a measured value of C d Ã = 4.4ϫ 10 −3 . 13 We consider a uniform channel of width b 0 with a localized contraction where b͑x͒ Ͻ b 0 is monotonically decreasing to a minimum nozzle width b͑x c ͒ = b c from x =0 to x = x c . In all experiments, this nozzle width occurs at the end of the channel and the contractions are linear.…”

Section: Multiple Steady States In Shallow Water Flows: 1d Theorymentioning

confidence: 99%

Hydraulic flow through a channel contraction: Multiple steady states

Akers

Bokhove

2008

Physics of Fluids

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We have investigated shallow water flows through a channel with a contraction by experimental and theoretical means. The horizontal channel consists of a sluice gate and an upstream channel of constant width b 0 ending in a linear contraction of minimum width b c . Experimentally, we observe upstream steady and moving bores/shocks, and oblique waves in the contraction, as single and multiple ͑steady͒ states, as well as a steady reservoir with a complex hydraulic jump in the contraction occurring in a small section of the b c / b 0 and Froude number parameter plane. One-dimensional hydraulic theory provides a comprehensive leading-order approximation, in which a turbulent frictional parametrization is used to achieve quantitative agreement. An analytical and numerical analysis is given for two-dimensional supercritical shallow water flows. It shows that the one-dimensional hydraulic analysis for inviscid flows away from hydraulic jumps holds surprisingly well, even though the two-dimensional oblique hydraulic jump patterns can show large variations across the contraction channel.

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Section: Multiple Steady States In Shallow Water Flows: 1d Theorymentioning

confidence: 99%

Hydraulic flow through a channel contraction: Multiple steady states

Akers

Bokhove

2008

Physics of Fluids

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“…In the full-depth hydrographic profiles the Medi'terranean water tongue is apparent as a layer of nearly constant salinity in the approximate 02 (potential temperature referenced to 2000 dbar) range of 8ø-10øC (see Figure 4) In the case of an inviscid steady two-dimensional flow along a channel of slowly varying geometry a horizontally asymmetric density distribution (i.e., differing reservoir conditions) implies that the flow is (hydraulically) controlled [Armi, 1986]. Pratt [1986] The simple one-and-a-half layer reduced gravity model with zero upstream potential vorticity introduced by Whitehead et al [1974] is considered adequate for this purpose, mainly because it is the simplest model of rotating hydraulics, which has been tested in similar contexts [Whitehead, 1997]. In the limit of no rotation it reduces to hydraulic flow over a weir.…”

Section: Regional Hydrography and Flow Fieldmentioning

confidence: 99%

Hydrography and high‐temperature heat flux of the Rainbow hydrothermal site (36°14′N, Mid‐Atlantic Ridge)

Thurnherr¹,

Richards²

2001

J. Geophys. Res.

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Abstract. On the basis of an extensive set of conductivity-temperature-depth, lowered acoustic Doppler current profiler (LADCP), and nephelometry profiles and tow-yos the hydrography, flow field, and particle plume of the Rainbow hydrothermal site on the Mid-Atlantic Ridge are analyzed. In the rift valley the water column is less dense and stratified than both eastern and western off-ridge water, with T/S characteristics consistent with inflow across a sill from the east. The buoyant hydrothermal plumes rise into a strong boundary current flowing along the slope of a topographic high which partially blocks the rift valley below 1950 m. The bulk of the neutrally buoyant plume is advected across a sill which forms both the narrowest and the shallowest part of the valley and acts as a hydraulic control point for the flow below 2000 m. Large-amplitude internal waves consistent with tidal forcing are observed near the sill, but LADCP measurements suggest that the tidal signal is not strong enough to lead to flow reversal at plume depth. Above 2000 rn the mean current across the topography generates lee waves which radiate energy upward and downstream. Density-averaged light-scattering profiles show the hydrothermal particle plume to be Gaussian in depth, even in the near field, where many of the individual profiles are characterized by multiple peaks and the horizontal variability is highest. The temperature anomalies associated with the mean near-source particle plume are of order -$ x 10 -3 øC; that is, the plume is cold/fresh as expected from the background hydrography of the deep Atlantic. Using the flow field, light-scattering, and hydrographic anomaly observations, the heat flux associated with the hydrothermal particle plume at Rainbow is estimated to lie between 1 and $ GW.

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“…All tidal adjustments of the interface occur near the constriction. The boundary condition is expressed thus: underneath an inactive layer [Pratt, 1986]; in both cases the control is moved landward of the topographic constriction, and the lower layer is thickened.…”

Section: Interfacial Mixingmentioning

confidence: 99%

“…The lower layer thickness must increase to conserve transport when currents are reduced; thins could also be interpreted as a relocation of the control point [Pratt, 1986] We have learned something about the effects of bottom friction and barotropic currents. In the absence of bottom friction, the pycnocline will be thicker on flood.…”

Section: Effect Of Interfacial Frictionmentioning

confidence: 99%