26 results found
Baker AL, Craighead RM, Jarvis EJ, et al., 2020, Modelling the impact of tidal energy on species communities, Ocean and Coastal Management, Vol: 193, ISSN: 0964-5691
Tidal energy has the potential to form a key component of the energy production in a number of countries, including the UK. Nonetheless, the deployment of tidal energy systems is associated with potential environmental impacts as prime resource sites often coincide with unique ecosystems inhabited by sensitive organisms. Previous studies have generally focused on the hydrodynamic impact of tidal energy schemes, i.e. how schemes alter the flow dynamics and sedimentary transport processes. Whilst these efforts are key in understanding environmental impacts, there is no straightforward step for translating sediment to faunal changes. Species distribution models offer methods to quantitatively predict certain possible impacts of tidal energy extraction. The River Severn is a distinguished candidate region for tidal energy in the UK featuring sites under stringent ecological protection regulations. We examine the impact of a proposed Severn tidal barrage on 14 species via the linking of hydrodynamic modelling to species distribution models. Through a selection of species that are linked via a simple food web system we extrapolate changes in prey species to the respective predator species. We show that species at lower trophic levels would be adversely affected by the barrage, but higher trophic level organisms increase in possible habitable area. Once food web relationships are acknowledged this increase in habitat area decreases, but is still net positive. Overall, all 14 species were affected, with most gaining in distribution area, and only four losing distribution area within the Severn Estuary. We conclude that a large-scale tidal barrage may have detrimental and complex impacts on species distribution, altering food web dynamics and altering food availability in the Severn Estuary. The methodology outlined herein can be transferred to the assessment and optimisation of prospective projects globally to aide in the sustainable introduction of the technology.
Dean CD, Collins DS, van Cappelle M, et al., 2019, Regional-scale paleobathymetry controlled location, but not magnitude, of tidal dynamics in the Late Cretaceous Western Interior Seaway, USA, Geology, Vol: 47, Pages: 1083-1087, ISSN: 0091-7613
<jats:title>Abstract</jats:title> <jats:p>Despite extensive outcrop and previous sedimentologic study, the role of tidal processes along sandy, wave- and river-dominated shorelines of the North American Cretaceous Western Interior Seaway remains uncertain, particularly for the extensive mid-Campanian (ca. 75–77.5 Ma) tidal deposits of Utah and Colorado, USA. Herein, paleotidal modeling, paleogeographic reconstructions, and interpretations of depositional process regimes are combined to evaluate the regional-scale (hundreds to thousands of kilometers) basin physiographic controls on tidal range and currents along these regressive shorelines in the “Utah Bight”, southwestern Western Interior Seaway. Paleotidal modeling using a global and astronomically forced tidal model, combined with paleobathymetric sensitivity tests, indicates the location of stratigraphic units preserving pronounced tidal influence only when the seaway had a deep center (∼400 m) and southern entrance (>100 m). Maximum tidal velocity vectors under these conditions suggest a dominant southeasterly ebb tide within the Utah Bight, consistent with the location and orientation of paleocurrent measurements in regressive, tide-influenced deltaic units. The modeled deep paleobathymetry increased tidal inflow into the basin and enhanced local-scale (tens to hundreds of kilometers) resonance effects in the Utah Bight, where an amphidromic cell was located. However, the preservation of bidirectional, mudstone-draped cross-stratification in fine- to medium-grained sandstones requires tides in combination with fluvial currents and/or local tidal amplification below the maximum resolution of model meshes (∼10 km). These findings suggest that while regional-scale controls govern tidal potential within basins, localized physiography exerts an important control on the preservation of tidal signatures in the geologic record.</jats:p>
Goss Z, Warder S, Angeloudis A, et al., 2019, Tidal modelling with Thetis: preliminary English Channel benchmarking, Tidal modelling with Thetis: preliminary English Channelbenchmarking
This report describes the application and benchmarking of the Thetis coastal ocean model fortidal modelling, and makes use of a test case based upon the English Channel. Comparisonsare made between model predictions and tide gauge data at a number of locations across theEnglish Channel. A preliminary investigation of the impact of mesh resolution and bathymetrydata is given. A demonstration is also provided of Thetis’s ability to use adjoint technologyto optimise model predictions through the assimilation of observational data. In the examplepresented here the bottom friction field is optimised to provide an improved match betweenthe model results and tide gauge data. This adjoint based optimisation capability may alsobe used to optimise the location, size and design of tidal power generation schemes.
Goss ZL, Piggott MD, Kramer SC, et al., 2019, Competition effects between nearby tidal turbine arrays—optimal design for alderney race, Pages: 255-262
© 2019 Taylor & Francis Group, London. Tidal renewable energy can be described as a fledgling industry, with the world’s pilot tidal stream turbine array only recently installed. Full-sized arrays will be developed if they prove their economic, engineering and environmental viability. Reliable numerical tools are needed to optimise power yields in arrays of potentially hundreds of turbines and assess viability of new sites and designs. To demonstrate our capability to optimise the number of turbines and their spatial distribution in a region, we focus on a test case based upon the Alderney Race. The site contains the majority of the Channel Islands resource with plans from both France and Alderney to develop adjacent arrays that could impact on each other. We present a shallow-water model of the English Channel using the Thetis ocean model. Together with the hydrodynamics modelling we employ adjoint technology to optimise the micrositing of turbines for a set of scenarios.
Collins D, Alvdis A, Allison P, et al., 2018, Controls on tidal sedimentation and preservation: insights from numerical tidal modelling in the late oligocene–miocene South China sea, Southeast Asia, Sedimentology, Vol: 65, Pages: 2468-2505, ISSN: 0037-0746
Numerical tidal modelling, when integrated with other geological datasets, can significantly inform the analysis of physical sedimentation processes and the depositional and preservational record of ancient tide-influenced shoreline–shelf systems. This is illustrated in the Oligo–Miocene of the South China Sea (SCS), which experienced significant changes in basin physiography and where tide-influenced, shoreline–shelf deposition is preserved in ca 10 sub-basins. Palaeogeographic reconstructions, palaeotidal modelling and regional sedimentary facies analysis have been integrated in order to evaluate the spatial–temporal evolution and physiographic controls on tidal sedimentation and preservation during the ca 25 Myr Oligo–Miocene record in the SCS. Palaeotidal modelling, using an astronomically forced and global tidal model (Fluidity) at a maximum 10 km resolution, indicates that spring tides along Late Oligocene–Middle Miocene coastlines were predominantly mesotidal– macrotidal and capable of transporting sand, which reflects two main conditions: (1) increased tidal inflow through wider ocean connections to the Pacific Ocean; and (2) tidal amplification resulting from constriction of the tidal wave in a ‘blind gulf’ type of basin morphology. Since the Middle–Late Miocene, a reduction in the amplitude and strength of tides in the SCS was mainly due to diminishing tidal inflow from the Pacific Ocean caused by the northward movement of the Philippines and Izu-Bonin-Mariana arc. Sensitivity tests to palaeogeographic and palaeobathymetric uncertainty indicate that regional–scale (100–1000s29 km) palaeogeographic changes influencing tidal inflow versus outflow can override local30scale (1–100s km) changes to tidal resonance and convergence effects (funnelling and shoaling), such as shelf width and shoreline geometry. Palaeotidal model results compare favourably to the distribution and sedimenta
Neill SP, Angeloudis A, Robins PE, et al., 2018, Tidal range energy resource and optimization - past perspectives and future challenges, Renewable Energy, Vol: 127, Pages: 763-778, ISSN: 0960-1481
Tidal energy is one of the most predictable forms of renewable energy. Although there has been much commercial and R&D progress in tidal stream energy, tidal range is a more mature technology, with tidal range power plants having a history that extends back over 50 years. With the 2017 publication of the “Hendry Review” that examined the feasibility of tidal lagoon power plants in the UK, it is timely to review tidal range power plants. Here, we explain the main principles of tidal range power plants, and review two main research areas: the present and future tidal range resource, and the optimization of tidal range power plants. We also discuss how variability in the electricity generated from tidal range power plants could be partially offset by the development of multiple power plants (e.g. lagoons) that are complementary in phase, and by the provision of energy storage. Finally, we discuss the implications of the Hendry Review, and what this means for the future of tidal range power plants in the UK and internationally.
Tidal range power plants represent an attractive approach for the large-scale generation of electricity from the marine environment. Even though the tides and by extension the available energy resource are predictable, they are also variable in time. This variability poses a challenge regarding the optimal transient control of power plants. We consider simulation methods which include the main modes of operation of tidal power plants, along with algorithms to regulate the timing of these. This paper proposes a framework where simplified power plant operation models are coupled with gradient-based optimisation techniques to determine the optimal control strategy over multiple tidal cycles. The optimisation results inform coastal ocean simulations that include tidal power plants to gauge whether the benefits of an adaptive operation are preserved once their hydrodynamic impacts are also taken into consideration. The combined operation of two prospective tidal lagoon projects within the Bristol Channel and the Severn Estuary is used as an example to demonstrate the potential benefits of an energy maximisation optimisation approach. For the case studies considered, the inclusion of pumping and an adaptive operation is shown to deliver an overall increase in energy output of 20–40% compared to a conventional two-way uniform operation. The findings also demonstrate that smaller schemes stand to gain more from operational optimisation compared to designs of a larger scale.
Avdis A, Candy AS, Hill J, et al., 2017, Efficient unstructured mesh generation for marine renewable energy applications, Renewable Energy, Vol: 116, Pages: 842-856, ISSN: 0960-1481
Renewable energy is the cornerstone of preventing dangerous climate change whilst maintaining a robust energy supply. Tidal energy will arguably play a critical role in the renewable energy portfolio as it is both predictable and reliable, and can be put in place across the globe. However, installation may impact the local and regional ecology via changes in tidal dynamics, sediment transport pathways or bathymetric changes. In order to mitigate these effects, tidal energy devices need to be modelled in order to predict hydrodynamic changes. Robust mesh generation is a fundamental component required for developing simulations with high accuracy. However, mesh generation for coastal domains can be an elaborate procedure. Here, we describe an approach combining mesh generators with Geographical Information Systems. We demonstrate robustness and efficiency by constructing a mesh with which to examine the potential environmental impact of a tidal turbine farm installation in the Orkney Islands. The mesh is then used with two well-validated ocean models, to compare their flow predictions with and without a turbine array. The results demonstrate that it is possible to create an easy-to-use tool to generate high-quality meshes for combined coastal engineering, here tidal turbines, and coastal ocean simulations.
Collins DS, Avdis A, Allison PA, et al., 2017, Tidal dynamics and mangrove carbon sequestration during the Oligo–Miocene in the South China Sea, Nature Communications, Vol: 8, ISSN: 2041-1723
Modern mangroves are among the most carbon-rich biomes on Earth, but their long-term (≥106 yr) impact on the global carbon cycle is unknown. The extent, productivity and preservation of mangroves are controlled by the interplay of tectonics, global sea level and sedimentation, including tide, wave and fluvial processes. The impact of these processes on mangrove-bearing successions in the Oligo–Miocene of the South China Sea (SCS) is evaluated herein. Palaeogeographic reconstructions, palaeotidal modelling, and facies analysis suggest that elevated tidal range and bed shear stress optimised mangrove development along tide-influenced tropical coastlines. Preservation of mangrove organic carbon (OC) was promoted by high tectonic subsidence and fluvial sediment supply. Lithospheric storage of OC in peripheral SCS basins potentially exceeded 4000 Gt (equivalent to 2000 ppm of atmospheric CO2). These results highlight the crucial impact of tectonic and oceanographic processes on mangrove OC sequestration within the global carbon cycle on geological timescales.
Pérez-Ortiz A, Borthwick AGL, McNaughton J, et al., 2017, Characterization of the tidal resource in Rathlin Sound, Renewable Energy, Vol: 114, Pages: 229-243, ISSN: 0960-1481
Tidal resource assessment is presented for Rathlin Sound, located between Rathlin Island and the north-east coast of Northern Ireland. The flow is simulated in 2D, using the shallow water equations. For an M2 tide, the natural flow conditions exhibit local spatial mean and maximum flow speeds of 2 and 3 m/s. Upper limits to power extraction are about 298 MW for M2 and 330 MW for M2+S2 tidal signals (different to undisturbed kinetic power and power naturally dissipated at the seabed). An analytical model of a channel connecting two infinite ocean basins underpredicts maximum power extracted in Rathlin Sound due to changes in head driving the flow and the existence of an alternative flow path. At maximum power extracted, there is substantial reduction in mean flow speeds in the strait and to the south-east of Rathlin Sound. In the strait, maximum power is reduced by 14% and 36% for blockage ratios of 80% and 60%. Power extraction both offshore of the island and in the strait yields higher power generation rates than isolated extraction. Resource assessments for Rathlin Sound are generally in good agreement with those for an idealised strait between an island and landmass.
Mouradian, Avdis A, Piggott M, et al., 2016, TELEMAC model archive: Integrating open-source tools for the management and visualisation of model data, 23rd TELEMAC-MASCARET User Conference (TUC-2016)
T Jacobs C, Avdis A, 2016, Git-RDM: A research data management plugin for the Git version control system, The Journal of Open Source Software, Vol: 1, ISSN: 2475-9066
Harris J, Ashley A, Healey F, et al., 2016, Palaeogeographic and Palaeoclimatic evolution of the north Atlantic: The role of earth systems modelling in the predictive mapping of source rock environments, International Conference and Exhibition, Barcelona, Spain, 3-6 April 2016, Publisher: Society of Exploration Geophysicists and American Association of Petroleum Geologists
Avdis A, Jacobs CT, Mouradian SL, et al., 2016, Meshing ocean domains for coastal engineering applications, ECCOMAS Congress 2016, Pages: 480-492
As we continue to exploit and alter the coastal environment, the quantification of the potential impacts from planned coastal engineering projects, as well as the minimisation of any detrimental effects through design optimisation, are receiving increasing attention. Geophysical fluid dynamics simulations can provide valuable insight towards the mitigation and prevention of negative outcomes, and as such are routinely used for planning, operational and regulatory reasons. The ability to readily create high-quality computational meshes is critical to such modelling studies as it impacts on the accuracy, efficiency and reproducibility of the numerical results. To that end, most (coastal) ocean modelling packages offer tailored mesh generation utilities. Geographical Information Systems (GIS) offer an ideal framework within which to process data for use in the meshing of coastal regions. GIS have been designed specifically for the processing and analysis of geophysical data and are a popular tool in both the academic and industrial sectors. On the other hand Computer Aided Design (CAD) is the most appropriate tool for designing coastal structures and is usually the user interface to generic three-dimensional mesh generation frameworks. In this paper we combine GIS and CAD with a view towards mesh generation for an impact study of the proposed Swansea Bay Tidal Lagoon project within the Bristol Channel and Severn Estuary. We demonstrate in this work that GIS and CAD can be used in a complementary way to deliver unstructured mesh generation capabilities for coastal engineering applications.
Bentley OL, Allison PA, Avdis A, et al., 2016, THE ROLE OF BATHYMETRY IN UPWELLING INDUCED PRODUCTIVITY IN ICEHOUSE AND GREENHOUSE WORLDS, GSA Annual Meeting in Denver, Colorado, USA - 2016, Publisher: Geological Society of America
Jacobs CT, Avdis A, Mouradian SL, et al., 2015, Integrating Research Data Management into Geographical Information Systems, http://ceur-ws.org/Vol-1529/, 5th International Workshop on Semantic Digital Archives (SDA 2015), Pages: 7-17
Ocean modelling requires the production of high-fidelity computational meshes upon which to solve the equations of motion. The production of such meshes by hand is often infeasible, considering the complexity of the bathymetry and coastlines. The use of Geographical Information Systems (GIS) is therefore a key component to discretising the region of interest and producing a mesh appropriate to resolve the dynamics. However, all data associated with the production of a mesh must be provided in order to contribute to the overall recomputability of the subsequent simulation. This work presents the integration of research data management in QMesh, a tool for generating meshes using GIS. The tool uses the PyRDM library to provide a quick and easy way for scientists to publish meshes, and all data required to regenerate them, to persistent online repositories. These repositories are assigned unique identifiers to enable proper citation of the meshes in journal articles.
Avdis A, Jacobs CT, Hill J, et al., 2015, Shoreline and Bathymetry Approximation in Mesh Generation for Tidal Renewable Simulations, European Wave & Tidal Energy
Due to the fractal nature of the domain geometry in geophysical flowsimulations, a completely accurate description of the domain in terms of acomputational mesh is frequently deemed infeasible. Shoreline and bathymetrysimplification methods are used to remove small scale details in the geometry,particularly in areas away from the region of interest. To that end, a novelmethod for shoreline and bathymetry simplification is presented. Existingshoreline simplification methods typically remove points if the resultantgeometry satisfies particular geometric criteria. Bathymetry is usuallysimplified using traditional filtering techniques, that remove unwanted Fouriermodes. Principal Component Analysis (PCA) has been used in other fields toisolate small-scale structures from larger scale coherent features in a robustway, underpinned by a rigorous but simple mathematical framework. Here wepresent a method based on principal component analysis aimed towardssimplification of shorelines and bathymetry. We present the algorithm in detailand show simplified shorelines and bathymetry in the wider region around theNorth Sea. Finally, the methods are used in the context of unstructured meshgeneration aimed at tidal resource assessment simulations in the coastalregions around the UK.
Jacobs CT, Avdis A, Mouradian SL, et al., 2015, Integrating research data management into geographical information systems, CEUR Workshop Proceedings, Vol: 1529, Pages: 7-17, ISSN: 1613-0073
Ocean modelling requires the production of high-fidelity com-putational meshes upon which to solve the equations of motion. The production of such meshes by hand is often infeasible, considering the complexity of the bathymetry and coastlines. The use of Geographical Information Systems (GIS) is therefore a key component to discretising the region of interest and producing a mesh appropriate to resolve the dynamics. However, all data abociated with the production of a mesh must be provided in order to contribute to the overall recomputability of the subsequent simulation. This work presents the integration of re-search data management in QMesh, a tool for generating meshes using GIS. The tool uses the PyRDM library to provide a quick and easy way for scientists to publish meshes, and all data required to regenerate them, to persistent online repositories. These repositories are abigned unique identifiers to enable proper citation of the meshes in journal articles.
Martin-Short R, Hill J, Kramer SC, et al., 2014, Tidal resource extraction in the Pentland Firth, UK: Potential impacts on flow regime and sediment transport in the Inner Sound of Stroma, Renewable Energy, Vol: 76, Pages: 596-607, ISSN: 1879-0682
Large-scale extraction of power from tidal streams within the Pentland Firth is expected to be underway in the near future. The Inner Sound of Stroma in particular has attracted significant commercial interest. To understand potential environmental impacts of the installation of a tidal turbine array a case study based upon the Inner Sound is considered. A numerical computational fluid dynamics model, Fluidity, is used to conduct a series of depth-averaged simulations to investigate velocity and bed shear stress changes due to the presence of idealised tidal turbine arrays. The number of turbines is increased from zero to 400. It is found that arrays in excess of 85 turbines have the potential to affect bed shear stress distributions in such a way that the most favourable sites for sediment accumulation migrate from the edges of the Inner Sound towards its centre. Deposits of fine gravel and coarse sand are indicated to occur within arrays of greater than 240 turbines with removal of existing deposits in the shallower channel margins also possible. The effects of the turbine array may be seen several kilometres from the site which has implications not only on sediment accumulation, but also on the benthic fauna.
Hill J, Collins GS, Avdis A, et al., 2014, How does multiscale modelling and inclusion of realistic palaeobathymetry affect numerical simulation of the Storegga Slide tsunami?, Ocean Modelling, Vol: 83, Pages: 11-25, ISSN: 1463-5003
The ∼8.15 ka Storegga submarine slide was a large (∼3000 km3), tsunamigenic slide off the coast of Norway. The resulting tsunami had run-up heights of around 10–20 m on the Norwegian coast, over 12 m in Shetland, 3–6 m on the Scottish mainland coast and reached as far as Greenland. Accurate numerical simulations of Storegga require high spatial resolution near the coasts, particularly near tsunami run-up observations, and also in the slide region. However, as the computational domain must span the whole of the Norwegian-Greenland sea, employing uniformly high spatial resolution is computationally prohibitive. To overcome this problem, we present a multiscale numerical model of the Storegga slide-generated tsunami where spatial resolution varies from 500 m to 50 km across the entire Norwegian-Greenland sea domain to optimally resolve the slide region, important coastlines and bathymetric changes. We compare results from our multiscale model to previous results using constant-resolution models and show that accounting for changes in bathymetry since 8.15 ka, neglected in previous numerical studies of the Storegga slide-tsunami, improves the agreement between the model and inferred run-up heights in specific locations, especially in the Shetlands, where maximum run-up height increased from 8 m (modern bathymetry) to 13 m (palaeobathymetry). By tracking the Storegga tsunami as far south as the southern North sea, we also found that wave heights were high enough to inundate Doggerland, an island in the southern North Sea prior to sea level rise over the last 8 ka.
Jacobs CT, Avdis A, Gorman GJ, et al., 2014, PyRDM: A Python-based Library for Automating the Management and Online Publication of Scientific Software and Data, Journal of Open Research Software, Vol: 2, ISSN: 2049-9647
Jacobs CT, Avdis A, Gorman GJ, et al., 2014, PyRDM
PyRDM is a Python-based library for research data management (RDM). It facilitates the automated publication of scientific software and associated input and output data.
Avdis A, Lardeau S, Leschziner M, 2009, Large Eddy Simulation of Separated Flow over a Two-dimensional Hump with and without Control by Means of a Synthetic Slot-jet, FLOW TURBULENCE AND COMBUSTION, Vol: 83, Pages: 343-370, ISSN: 1386-6184
Fishpool G, Avdis A, Leschziner M, 2008, Identification and Removal of Numerical Instability Components in Low-order LES Schemes
Hill J, Avdis A, Mouradian S, et al., Was Doggerland catastrophically flooded by the Mesolithic Storegga tsunami?
Myths and legends across the world contain many stories of deluges andfloods. Some of these have been attributed to tsunami events. Doggerland in thesouthern North Sea is a submerged landscape thought to have been heavilyaffected by a tsunami such that it was abandoned by Mesolithic humanpopulations at the time of the event. The tsunami was generated by the Storeggasubmarine landslide off the Norwegian coast which failed around 8150 years ago.At this time there were also rapid changes in sea level associated withdeglaciation of the Laurentide ice sheet and drainage of its large proglaciallakes, with the largest sea level jumps occurring just prior to the Storeggaevent. The tsunami affected a large area of the North Atlantic leavingsedimentary deposits across the region, from Greenland, through the Faroes, theUK, Norway and Denmark. From these sediments, run-up heights of up to 20 metreshave been estimated in the Shetland Isles and several metres on mainlandScotland. However, sediments are not preserved everywhere and so reconstructinghow the tsunami propagated across the North Atlantic before inundating thelandscape must be performed using numerical models. These models can also beused to recreate the tsunami interactions with now submerged landscapes, suchas Doggerland. Here, the Storegga submarine slide is simulated, generating atsunami which is then propagated across the North Atlantic and used toreconstruct the inundation on the Shetlands, Moray Firth and Doggerland. Theuncertainty in reconstructing palaeobathymetry and the Storegga slide itselfresults in lower inundation levels than the sediment deposits suggest. Despitethese uncertainties, these results suggest Doggerland was not as severelyaffected as previous studies implied. It is suggested therefore that theabandonment of Doggerland was primarily caused by rapid sea level rise prior tothe tsunami event.
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