Effects of viscosity and bottom friction on recirculating flows

Denniss, Tom; Middleton, Jason H.

doi:10.1029/93jc03588

Cited by 20 publications

(4 citation statements)

References 16 publications

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“…Research on wakes or eddies generated downstream of headlands has been primarily based on numerical models (Maddock & Pingree 1978;Pingree & Maddock 1979;Black & Gay 1987;Freeland 1990;Denniss & Middleton 1994). Galloway et al (1996) compared four classical 3-dimensional models with observations from 26 current meters in the wake of Rattray Island.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of a 3‐dimensional, baroclinic, headland eddy

Black¹,

Oldman²,

Hume³

2005

New Zealand Journal of Marine and Freshwater Research

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Wave, current, and temperature measurements from the north side of Cape Rodney, northeastern New Zealand, over a 6-week field programme, reveal the detailed internal dynamics of a baroclinic eddy. The measurements include water levels, currents, and water temperatures through the water column and seabed descriptions. A detailed calibration of a 3-dimensional numerical model leads to further examination of the flow and density structure within the eddy, in plan and cross-section. The eddy stretches c. 5 km along the northern side of the headland and is of the order of 1.5-2.0 km wide. The eddy currents are strongest near the bed and against the coast. The eddy is characteristically complex and vertical eddies readily form in parts of the water column during different phases of the tide, although these internal eddies rarely penetrate through the full depth. The dynamics near the surface and near the bed are significantly different and the structure of the eddy is often partitioned vertically and is strongly affected by wind.

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Section: Introductionmentioning

confidence: 99%

Dynamics of a 3‐dimensional, baroclinic, headland eddy

Black¹,

Oldman²,

Hume³

2005

New Zealand Journal of Marine and Freshwater Research

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“…The oscillatory nature of the incident tidal current provides a strong constraint on the wake development (Black and Gay 1986). This precludes any comparison with the traditional wake structures caused by steady incident flows such as the von Karman vortex street or the formation of steady recirculating eddies (Denniss and Middleton 1994;Chen and Jirka 1995).…”

Section: Discussionmentioning

confidence: 99%

Entrainment and advection in an island's tidal wake, as revealed by light attenuance, zooplankton, and ichthyoplankton

Suthers

Taggart

Kelley

et al. 2004

Limnology & Oceanography

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Spatial and temporal patterns of light attenuance, zooplankton abundance, and larval fish assemblages observed at night in the flood tide wake of a 2-km-wide, steep-sided island within the Great Barrier Reef lagoon (40-45-m local depth) are compared with two simple models. Eddy upwelling is shown to be slow relative to erosion, vertical entrainment, and advection (EA) arising near the flanks of the island, where currents were accelerated to 1-2 m s Ϫ1 , approximately twice that in the free stream. Turbidity (particles Ͻ300-m equivalent spherical diameter [ESD], inferred from increased water column light attenuance of an optical plankton counter) and medium-sized zooplankton (700-1,000-m ESD) appeared to be entrained toward the surface, to form a V-shaped plume. The plume originated near the island's flanks and converged 4 km downstream. Here, light attenuance returned to the free stream conditions, presumably as sediments settled, leaving a patch of medium-sized zooplankton that had a three-to fourfold greater biomass concentration than the free stream. A decrease in the concentration of small zooplankton (300-500-m ESD, generally found in surface waters) is also consistent with vertical mixing by EA. Neuston net collections across the wake revealed two larval fish assemblages that were correlated with either the small surface zooplankton or with the deeper, medium-sized zooplankton, which included epibenthic taxa. If EA is a common process for patch formation in tidal waters, then the geometry of the associated plumes may predict larval settlement (recruitment ''hotspots'') in shallow tidal waters.Swirls of turbidity in the wakes of small islands are distinctive features within shallow, tidally energetic areas such as the Great Barrier Reef lagoon (Hamner and Hauri 1977; Wolanski et al. 1984a,b). Wakes of this nature may extend downstream several island diameters within the semidiurnal tidal excursion, and they may exist for periods of 4-5 h (Black and Gay 1986;Signell and Geyer 1991). Wakes may AcknowledgmentsWe are grateful to the crew and captain of the RV Franklin, along with the Commonwealth Scientific and Industrial Research Organisation personnel who contributed to the success of the cruise. We acknowledge constructive discussions with C. Reiss and K. Thompson at Dalhousie University and two anonymous reviewers. GeoScience Australia, the National Tidal Facility at Flinders University and B. Petrie assisted with bathymetry data and tidal interpretation. We thank R. Piola and S. Murray for the zooplankton analyses.Funding was provided by the Australian Research Council; the Department of Industry, Trade and Commerce; the Australian Geographic magazine; Focal Technologies; the Canada Department of Fisheries and Oceans; and the Natural Sciences and Engineering Research Council of Canada. enhance mixing (Townsend et al. 1983) and modify sediment transport, thus influencing the bathymetry. Wakes can also have biological consequences that affect species-diversity gradients and plankton patchiness Hauri...

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“…However, a number of alternatives have also been suggested, such as the "wake stability parameter" of Ingram and Chu (1987). Denniss and Middleton (1994) derive three different parameters, based upon slightly different formulations of bottom friction, and conclude that the actual form of the friction is unimportant to the types of wake formed and the parameter value at which they occur. Tomczak (1988) reasserts the relevance of the Reynolds number (based upon horizontal friction coefficients), by considering the ratio of inertial to viscous forces.…”

Section: Non-dimensional Parametersmentioning

confidence: 98%

Idealised flow past an island in a dynamically adaptive finite element model

2010

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The problem of flow separation around islands is investigated using a dynamically adaptive finite element model to allow for resolution of the shear layers that form in the advent of separation. The changes in secondary circulation and vertical motion that occur in both attached and separated flows are documented, as is the degree of closure of the wake eddies. In the numerical experiments presented, the strongest motion always takes place at the sides of the idealised island, where flow curvature and shear act together to induce ascent. In contrast, it is the slower motion within the wake eddies that allow streamlines to extend from the bottom to the surface. We find no evidence for closure of the wake eddies. Rather, all of our separated experiments show that streamlines that pass through the eddies originate outside of the shear layers and frictional boundary layers on the upstream side of the idealised island. The numerical experiments demonstrate the potential for dynamically adaptive, unstructured meshes to resolve the separated shear layers that occur downstream of the idealised island, as well as the narrow boundary layers that form on the island itself.

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Effects of viscosity and bottom friction on recirculating flows

Cited by 20 publications

References 16 publications

Dynamics of a 3‐dimensional, baroclinic, headland eddy

Dynamics of a 3‐dimensional, baroclinic, headland eddy

Entrainment and advection in an island's tidal wake, as revealed by light attenuance, zooplankton, and ichthyoplankton

Idealised flow past an island in a dynamically adaptive finite element model

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