Observations and simulations of an unsteady island wake in the Firth of Forth, Scotland

Neill, Simon P.; Elliott, A.J.

doi:10.1007/s10236-003-0084-1

Cited by 29 publications

(14 citation statements)

References 10 publications

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“…The Reynolds number (Re) has been commonly used to describe the characteristics of island wakes, especially in experimental studies, because Re is based on the kinematic viscosity of the fluid and frictional boundary layers, which are generated in the laboratory by friction and boundary layer separation [49]. However, in real environmental flows, it is the turbulent viscosity which dominates the wake development [50]; therefore, Re is not suitable to quantify the characteristics of wakes since Re is based on the kinematic viscosity of the fluid. Subsequently, the wake behind an island in reality is often described by the island wake parameter [13], namely, P = (18) where U0 is the free stream velocity, D is the water depth, L is the diameter of island, and Kz is the vertical eddy diffusion coefficient.…”

Section: The Evolution Of Wake In the Lee Of Islandmentioning

confidence: 99%

“…For Flat Holm island, the island diameter (L) is about 700 m and kept constant during the rise and fall of tide due to its steep cliff. While the vertical eddy viscosity (K z ) in the Bristol Channel is defined as 0.20 m 2 s −1 [50,51]. The free stream velocity U 0 and water depth are taken at 400 m upstream away from Flat Holm Island.…”

Section: The Evolution Of Wake In the Lee Of Islandmentioning

confidence: 99%

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Studying the Wake of an Island in a Macro-Tidal Estuary

Guo

Ahmadian

Evans

et al. 2020

Water

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Tidal flow can generate unsteady wakes, large eddies, and recirculation zones in the lee or around complex natural and artificial obstructions, such as islands, headlands, or harbours. It is essential to understand the flow patterns around such structures given the potential impacts they can have on sedimentation, the marine environment, ecology, and anthropogenic activities. In this paper, the wake around an island in a macro-tidal environment has been studied using a widely used hydro-environmental model, Telemac-2D. Current data collected using moored acoustic Doppler current profilers (ADCPs) were used to validate and refine the Telemac-2D model. Four different turbulence models and several different solver options for the k- ε model were tested in this study to assess which representation could best replicate the hydrodynamics. The classic k- ε model with the solver of conjugate residual was the most suitable method to simulate the wake in the lee of the island. The model results showed good correlation with measured data. The island wake parameter used to predict the wake behaviour and its predictions matched the model results for different tidal conditions, suggesting that the island wake parameter could be used to predict the wake behind obstacles in macro-tidal environments. The model predictions showed the development of a wake is similar between ebb and flood tides in the neap tide while showing more difference in spring tide. With the increase of velocity in the neap tide, two side-by-side vortices will appear and then changing to stable Karman Vortex Street. During the ebb phase of spring tide, the wake will develop from a stable vortex to an unstable Karman Vortex Street, while the wake remained stable with two vortices during an flood tide.

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Section: The Evolution Of Wake In the Lee Of Islandmentioning

confidence: 99%

Section: The Evolution Of Wake In the Lee Of Islandmentioning

confidence: 99%

Studying the Wake of an Island in a Macro-Tidal Estuary

Guo

Ahmadian

Evans

et al. 2020

Water

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“…A single TEC, for example of the horizontal axis configuration, is composed of a support structure and a rotor. The support structure alone will generate a wake, possibly characterised by eddy shedding, analogous to the flow past a bridge pier or a small island (e.g., Neill and Elliott, 2004a;Neill and Elliott, 2004b). Flow past the support structure will influence sediment dynamics in two ways.…”

Section: Individual Tidal-stream Devicesmentioning

confidence: 99%

The Impact of Marine Renewable Energy Extraction on Sediment Dynamics

Neill

Robins

Fairley

2017

Marine Renewable Energy

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The extraction of marine energy, through either tidal or wave array operation, will clearly influence the hydrodynamics of a region. Although the influence on tidal currents and wave properties is likely to be very small for most extraction scenarios, the influence on bed shear stress is likely to be greater, because bed shear stress is quadratically related to tidal currents and wave orbital velocities. Further, the transport of sediments is a function of tidal current and wave orbital velocity cubed. Therefore, even small modifications to the flow field through tidal or wave array operation could lead to significant impacts on regional sediment dynamics. In this chapter, after providing an introduction to sediment dynamics in the marine environment, we explore the impact of tidal energy devices/arrays on regional sediment dynamics, with a particular emphasis on offshore sand banks-important sedimentary systems that protect our coastlines from the full impact of storm waves. Next, we discuss how generating electricity from waves could influence nearshore sediment processes, such as beach erosion or replenishment, over a range of time scales. To assess the magnitude of impacts on sedimentary systems, it is essential to consider the scale of the impact in relation to the range of natural variability. We suggest ways in which impacts can be assessed using numerical models, tuned by in situ measurements, that quantify variability over a range of time scales from individual storm events and lunar cycles to seasonal and interannual periods. We also

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“…In order to inform this research effort, it is first necessary to have a full understanding of the impact of operation of a TEC device or 'farm' of devices on the tidal physics themselves. This then enables consideration of the Manuscript [1,2,3,4,5]. The model shares a common heritage with other SWE solvers that are typically adopted in the academic and industrial community as the standard workhorses in estuarine and coastal modelling applications (e.g.…”

Section: Introductionmentioning

confidence: 99%

Large-scale physical response of the tidal system to energy extraction and its significance for informing environmental and ecological impact assessment

Couch

Bryden

2007

OCEANS 2007 - Europe

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The impact of harvesting tidal energy on the underlying tidal hydrodynamics is examined. Understanding of both the near-and far-field physical response of the tidal system is necessary in order to inform environmental and ecological impact assessment. A number of numerical model test cases are presented which provide first stage indications of the potential response of the system. impact of conditions altered by energy harvesting on the physics, biology and chemistry ofthe system.The majority of analyses on the impact of the harvesting of tidal energy have thus far focused on improving understanding of TEC device operation, and the near-field impact of a specific device on its surroundings. This area is further explored, and extended to consideration of larger-scale effects of energy extraction on the hydrodynamic system.

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Observations and simulations of an unsteady island wake in the Firth of Forth, Scotland

Cited by 29 publications

References 10 publications

Studying the Wake of an Island in a Macro-Tidal Estuary

Studying the Wake of an Island in a Macro-Tidal Estuary

The Impact of Marine Renewable Energy Extraction on Sediment Dynamics

Large-scale physical response of the tidal system to energy extraction and its significance for informing environmental and ecological impact assessment

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