Gravity currents produced by lock exchange

Shin, Jonathan; Dalziel, Stuart B.; Linden, P. F.

doi:10.1017/s002211200400165x

Cited by 380 publications

(444 citation statements)

References 21 publications

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“…Several laboratory studies have been based on image analysis techniques to investigate the dynamics of gravity currents [2,25,33,34,36,54] the last two with the very same apparatus herein used). Recent advances in measurement techniques have enabled velocity and density measurements within gravity currents.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of the head of gravity currents

et al. 2013

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The present work experimentally investigates the dynamics of unsteady gravity currents produced by lock-release of a saline mixture into a fresh water tank. Seven different experimental runs were performed by varying the density of the saline mixture in the lock and the bed roughness. Experiments were conducted in a Perspex flume, of horizontal bed and rectangular cross section, and recorded with a CCD camera. An image analysis technique was applied to visualize and characterize the current allowing thus the understanding of its general dynamics and, more specifically, of the current head dynamics. The temporal evolution of both head length and mass shows repeated stretching and breaking cycles: during the stretching phase, the head length and mass grow until reaching a limit, then the head becomes unstable and breaks. In the instants of break, the head aspect ratio shows a limit of 0.2 and the mass of 123Environ Fluid Mech the head is of the order of the initial mass in the lock. The average period of the herein called breaking events is seen to increase with bed roughness and the spatial periodicity of these events is seen to be approximately constant between runs. The rate of growth of the mass at the head is taken as a measure to assess entrainment and it is observed to occur at all stages of the current development. Entrainment rate at the head decreases in time suggesting this as a phenomenon ruled by local buoyancy and the similarity between runs shows independence from the initial reduced gravity and bed roughness.

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Section: Introductionmentioning

confidence: 99%

Dynamics of the head of gravity currents

et al. 2013

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“…Fig. 5 Frontal speed of the 2D inviscid model compared with the laboratory experimental data by Marino et al [15] and the hydraulic theory of Shin et al [23]. The red open circles denote the front speed at the end of the acceleration phase obtained from tracing back the LBS data in Fig.…”

Section: Front Speed At the Leading Edgementioning

confidence: 93%

“…This theory by Shin et al [23] and the experimental data of Marino et al [15] are included in Fig. 5 to compare with the front speeds at the end of the acceleration phase obtained [23] does not include the entrainment.…”

Section: Front Speed At the Leading Edgementioning

confidence: 99%

“…4 are the front speeds at the end of the acceleration phase that are obtained by tracing back to the initial positions at x f = L o . Shin et al [23] and Marino et al [15] have examined the role of the ambient current on the front speed. Shin et al [23] developed a hydraulic theory to correlate the front-speed Froude number to the dam-to-tank height ratio H/H tank by the formula:…”

Section: Front Speed At the Leading Edgementioning

confidence: 99%

“…5 to compare with the front speeds at the end of the acceleration phase obtained [23] does not include the entrainment. It is therefore not surprising that applying their theory gives a slightly higher front speed than occurs in the results of the experimental data of Marino et al [15] and the results of the present simulations.…”

Section: Front Speed At the Leading Edgementioning

confidence: 99%

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A two-dimensional inviscid model of the gravity-current head by Lagrangian block simulation

Chu

Altai

2017

Environ Fluid Mech

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A two-dimensional inviscid model of the gravity-current head produced by the release of a relatively small volume of dense fluid from behind a tall lock gate is constructed by Lagrangian block simulation. Three numerical experiments are conducted for the lock's height-to-length aspect ratios H/L o = 8, 4 and 2. The front speeds obtained by the simulations agree with the laboratory observation for a similar range of aspect ratios. The floor velocity in the wake behind these heads is found to be greater than their front speed. The high floor velocity is caused by the impingement of the coherent wake vortex on the floor. It is a condition that permits these gravity-current heads to maintain their structural integrity so that the fine sediments can travel with the head over long distances on the ocean floor. The structural coherence of the current head depends on the lock aspect ratio. The gravity-current head produced by the release from the lock with the highest aspect ratio of H/L o = 8 is most coherent and relatively has the greatest floor velocity and the least trailing current behind the head.Keywords Gravity-current head Á Coherent wake vortex Á 2D inviscid model Á Lagrangian block advection Á Streamfunction and vorticity formulation

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An anomalous near-bottom cross-shelf intrusion of slope water on the southern New England continental shelf

Ullman

Codiga

Pfeiffer-Herbert

et al. 2014

J. Geophys. Res. Oceans

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Hydrographic surveys and moored observations in Rhode Island Sound (RIS) in water depths of 30-50 m, off the southern New England coast, revealed a near-bottom intrusion of anomalously warm and saline water in late fall 2009. The properties of this water mass, with peak salinity of nearly 35, are typical of slope water that is normally found offshore of the shelfbreak front, located approximately 100 km to the south. The slope water intrusion, with a horizontal spatial scale of about 45 km, appears to have been brought onto the outer shelf during the interaction of a Gulf Stream warm core ring with the shelfbreak east (upshelf) of RIS. The along-shelf transport rate of the intrusion can be explained as due to advection by the mean outer-shelf along-isobath current, although the transit time of the intrusion is also consistent with the self-advection of a dense bolus on a sloping shelf. The mechanism responsible for the large onshore movement of the intrusion from the outer shelf is not entirely clear, although a wind-driven upwelling circulation appeared to be responsible for its final movement into the RIS region. Depth-averaged salinity at all RIS mooring sites increased by 0.5-1 over the 3-4 week intrusion period suggesting that the intrusion mixed irreversibly, at least partially, with the ambient shelf water. The mixing of the salty intrusion over the shelf indicates that net cross-isobath fluxes of salt and other water properties have occurred.

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Gravity currents produced by lock exchange

Cited by 380 publications

References 21 publications

Dynamics of the head of gravity currents

Dynamics of the head of gravity currents

A two-dimensional inviscid model of the gravity-current head by Lagrangian block simulation

An anomalous near-bottom cross-shelf intrusion of slope water on the southern New England continental shelf

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