The Alderney Race: general hydrodynamic and particular features

Bois, Pascal Bailly du; Dumas, Franck; Morillon, Mehdi; Furgerot, Lucille; Voiseux, Claire; Poizot, Emmanuel; Méar, Yann; Bennis, Anne-Claire

doi:10.1098/rsta.2019.0492

Cited by 10 publications

(6 citation statements)

References 38 publications

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“…These works paved the way for more recent studies such as [15][16][17]. Very recently, and crucially for this paper dealing with the Alderney Race, the results of mainly two French research programs (THYMOTE and HYD2M) were published, most of them in a special issue of the Philosophical Transaction of the Royal Society A [18][19][20][21][22][23][24][25]. All these works will be extremely valuable for the forthcoming computations applied to farm configurations in the Alderney Race and specifically for the configuration treated in the present paper.…”

Section: Introductionmentioning

confidence: 94%

Lagrangian Vortex Computations of a Four Tidal Turbine Array: An Example Based on the NEPTHYD Layout in the Alderney Race

et al. 2021

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This study investigates the wake interaction of four full-scale three-bladed tidal turbines with different ambient turbulence conditions, in straight and yawed flows. A three-dimensional unsteady Lagrangian Vortex Blob software is used for the numerical simulations of the turbines’ wakes. In order to model the ambient turbulence in the Lagrangian Vortex Method formalism, a Synthetic Eddy Method is used. With this method, turbulent structures are added in the computational domain to generate a velocity field which statistically reproduces any ambient turbulence intensity and integral length scale. The influence of the size of the structures and their density (within the study volume) on the wake of a single turbine is studied. Good agreement is obtained between numerical and experimental results for a high turbulence intensity but too many structures can increase the numerical dissipation and reduce the wake extension. Numerical simulations of the four turbine array with the layout initially proposed for the NEPTHYD pilot farm are then presented. Two ambient turbulence intensities encountered in the Alderney Race and two integral length scales are tested with a straight flow. Finally, the wakes obtained for yawed flows with different angles are presented, highlighting turbine interactions.

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Section: Introductionmentioning

confidence: 94%

Lagrangian Vortex Computations of a Four Tidal Turbine Array: An Example Based on the NEPTHYD Layout in the Alderney Race

et al. 2021

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“…14 m) appear in the Gulf of Mont Saint Michel, and decrease towards the north to amplitudes between 6 and 10 m in the Alderney Race. There, the mean tidal range has been shown to present large horizontal gradients that reach 0.4 m km −1 in front of Cap de La Hague [3]. Similarly, water levels show large horizontal variations due to the strong gradients generated by the presence of the Channel Islands, and contribute to accelerating the current [2].…”

Section: Introductionmentioning

confidence: 99%

Surface currents in the Alderney Race from high-frequency radar measurements and three-dimensional modelling

Lopez

Bennis

Barbin

et al. 2020

Phil. Trans. R. Soc. A.

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Two weeks of high-frequency radar measurements collected at the Alderney Race are compared with the results of a three-dimensional fully coupled wave–current model. Spatial current measurements are rare in this site, otherwise well investigated through modelling. Thus, the radar measurements offer a unique opportunity to examine the spatial reliability of numerical results, and can help to improve our understanding of the complex currents in the area. Comparison of observed and modelled surface current velocities showed a good agreement between the methods, represented by root mean squared errors ranging from 14 to 40 cm s −1 and from 18 to 60 cm s −1 during neap and spring tides, respectively. Maximum errors were found in shallow regions with consistently high current velocities, represented by mean neap and spring magnitudes of 1.25 m s −1 and 2.7 m s −1 , respectively. Part of the differences between modelled and observed surface currents in these areas are thought to derive from limitations in the k-epsilon turbulence model used to simulate vertical mixing, when the horizontal turbulent transport is high. In addition, radar radial currents showed increased variance over the same regions, and might also be contributing to the discrepancies found. Correlation analyses yielded magnitudes above 0.95 over the entire study area, with better agreement during spring than during neap tides, probably because of an increase in the phase lag between radar and model velocities during the latter. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

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“…Background shading represents the maximum current speed flood from numerical simulations by regional model MARS-2D (e.g. [22]). ( b ) Summary of the measurement setup and periods of data acquisition in the Alderney Race from 21 April 2017 to 6 July 2018.…”

Section: Data and Methods Of Analysismentioning

confidence: 99%

One year of measurements in Alderney Race: preliminary results from database analysis

Furgerot¹,

Sentchev

Bois³

et al. 2020

Phil. Trans. R. Soc. A.

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The Alderney Race is assumed to have the largest tidal-stream energy potential in the north-western European coastal seas. Interaction of the powerful tidal stream with strong wind, high waves and irregular bathymetry creates hydrodynamic conditions of extreme complexity, with high levels of turbulence. A comprehensive dataset has been created to improve the understanding of physical processes, turbulence, tidal stream and resource variability at the site. The database contains a large amount of oceanographic and meteorological measurements acquired in Alderney Race in 2017–2018. This exceptionally long period of observations (nearly one year) became possible due to modern tools and strategies of data acquisition. The paper presents some significant results from the database analysis. Among many results, we would like to underline the following: (i) a wide range of variability of mean flow and sea state parameters was documented; (ii) exceptionally large values of current velocity (7 m s −1 ) and significant wave height (8 m) were measured during extreme meteorological conditions; (iii) high-frequency variability of current speed during storm events was also found to be very large, with the standard deviation of velocity reaching 0.3 m s −1 in the bottom boundary layer, and 0.6 m s −1 in the surface layer; and (iv) predominant wind and wave direction relative to the flow impacts the wave height and significantly increases the turbulence kinetic energy of the flow. To our knowledge, this is the largest multi-variable database available on potential tidal energy sites. The results of database analysis can represent a significant advance in environmental conditions and resource characterization and provide advanced information to turbine developers. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

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The Alderney Race: general hydrodynamic and particular features

Cited by 10 publications

References 38 publications

Lagrangian Vortex Computations of a Four Tidal Turbine Array: An Example Based on the NEPTHYD Layout in the Alderney Race

Lagrangian Vortex Computations of a Four Tidal Turbine Array: An Example Based on the NEPTHYD Layout in the Alderney Race

Surface currents in the Alderney Race from high-frequency radar measurements and three-dimensional modelling

One year of measurements in Alderney Race: preliminary results from database analysis

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