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Dr. Athanasios Angeloudis
University of Edinburgh

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0 Civil Engineering
0 Coastal Engineering
0 Tidal Energy
0 Marine Hydrodynamics
0 Environmental fluid mechanics

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Preprint content
Published: 19 May 2021
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The modelling of a tidal array farm is an inherently multi-scale endeavour. It requires the simultaneous resolution of tidal processes across tens or hundreds of kilometres of coastal ocean (including estuaries, or even entire seas), the hydrodynamics in the neighbourhood of the farm (hundreds of metres), the wakes of individual turbines (metres, or tens of metres) and device hydrodynamics (sub-metre). As such, the construction of an accurate, computationally efficient numerical model requires careful consideration of the underlying discretisation. In this paper, we apply time-dependent mesh adaptation techniques based on the Riemannian metric framework to an idealised tidal array and assess the quality of the resulting approximations. Whilst classical hierarchical mesh adaptation methods modify mesh element/cell size in order to improve resolution locally, the metric-based approach also allows for control of element shape and orientation, which can be especially advantageous for advection-dominated problems. Metrics are normalised in such a way that the resulting discretisation is multi-scale in both space and time as per Alauzet and Olivier (2010). Typically, metrics are constructed from recovered derivatives of solution fields, such as fluid vorticity. Alternatively, metrics may be derived from goal-oriented error estimates, enabling accurate estimation of a diagnostic quantity of interest (QoI). In the context of tidal farm modelling, one clear QoI is the power output. Building upon the idealised steady-state test case considered in Wallwork et al. (2020), which represents turbines using a drag parametrisation in a depth-averaged shallow water model, we demonstrate here that goal-oriented mesh adaptation can be used to obtain an accurate approximation of tidal farm power output using relatively few overall degrees of freedom.

ACS Style

Joseph Wallwork; Lucas Mackie; Stephan C Kramer; Nicolas Barral; Athanasios Angeloudis; Matthew Piggott. Goal-Oriented Metric-Based Mesh Adaptive Tidal Farm Modelling. 2021, 1 .

AMA Style

Joseph Wallwork, Lucas Mackie, Stephan C Kramer, Nicolas Barral, Athanasios Angeloudis, Matthew Piggott. Goal-Oriented Metric-Based Mesh Adaptive Tidal Farm Modelling. . 2021; ():1.

Chicago/Turabian Style

Joseph Wallwork; Lucas Mackie; Stephan C Kramer; Nicolas Barral; Athanasios Angeloudis; Matthew Piggott. 2021. "Goal-Oriented Metric-Based Mesh Adaptive Tidal Farm Modelling." , no. : 1.

Editorial
Published: 25 April 2021 in Water
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Environmental Hydraulics (EH) is the scientific study of environmental water flows and their related transport and transformation processes affecting the environmental quality of natural water systems, such as rivers, lakes, and aquifers, on our planet Earth

ACS Style

Carlo Gualtieri; Dongdong Shao; Athanasios Angeloudis. Advances in Environmental Hydraulics. Water 2021, 13, 1192 .

AMA Style

Carlo Gualtieri, Dongdong Shao, Athanasios Angeloudis. Advances in Environmental Hydraulics. Water. 2021; 13 (9):1192.

Chicago/Turabian Style

Carlo Gualtieri; Dongdong Shao; Athanasios Angeloudis. 2021. "Advances in Environmental Hydraulics." Water 13, no. 9: 1192.

Journal article
Published: 19 February 2021 in Energies
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This study quantifies the technical, economic and environmental performance of hybrid systems that use either a tidal stream or wind turbine, alongside short-term battery storage and back-up oil generators. The systems are designed to partially displace oil generators on the island of Alderney, located in the British Channel Islands. The tidal stream turbine provides four power generation periods per day, every day. This relatively high frequency power cycling limits the use of the oil generators to 1.6 GWh/year. In contrast, low wind resource periods can last for days, forcing the wind hybrid system to rely on the back-up oil generators over long periods, totalling 2.4 GWh/year (50% higher). For this reason the tidal hybrid system spends £0.25 million/year less on fuel by displacing a greater volume of oil, or £6.4 million over a 25 year operating life, assuming a flat cost of oil over this period. The tidal and wind hybrid systems achieve an oil displacement of 78% and 67% respectively (the same as the reduction in carbon emissions). For the wind hybrid system to displace the same amount of oil as the tidal hybrid system, two additional wind turbines are needed. The ability of the battery to store excess turbine energy during high tidal/wind resource periods relies on opportunities to regularly discharge stored energy. The tidal hybrid system achieves this during slack tides. Periods of high wind resource outlast those of high tidal resource, causing the battery to often remain fully charged and excess wind power to be curtailed. Consequently the wind hybrid system curtails 1.9 GWh/year, whilst the tidal turbine curtails 0.2 GWh/year. The ability of the tidal stream turbines to reduce curtailment, fuel costs and carbon emissions may provide a case for implementing them in hybrid systems, if these benefits outweigh their relatively high capital and operating expenditure.

ACS Style

Daniel Coles; Athanasios Angeloudis; Zoe Goss; Jon Miles. Tidal Stream vs. Wind Energy: The Value of Cyclic Power When Combined with Short-Term Storage in Hybrid Systems. Energies 2021, 14, 1106 .

AMA Style

Daniel Coles, Athanasios Angeloudis, Zoe Goss, Jon Miles. Tidal Stream vs. Wind Energy: The Value of Cyclic Power When Combined with Short-Term Storage in Hybrid Systems. Energies. 2021; 14 (4):1106.

Chicago/Turabian Style

Daniel Coles; Athanasios Angeloudis; Zoe Goss; Jon Miles. 2021. "Tidal Stream vs. Wind Energy: The Value of Cyclic Power When Combined with Short-Term Storage in Hybrid Systems." Energies 14, no. 4: 1106.

Journal article
Published: 12 January 2021 in Ocean & Coastal Management
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With increased nutrient inputs to estuaries in recent decades exacerbating their susceptibility to eutrophication, assessment of the response of individual estuaries to nutrient enrichment is attracting considerable attention. Nonetheless, the impact of tidal energy extraction on estuarine nutrient dynamics and the risk of eutrophication has been largely overlooked despite the detrimental consequences of eutrophication on ecosystem functioning. It is understood that tidal energy schemes such as the tidal lagoon previously proposed in Swansea Bay would alter tidal flow characteristics, potentially having knock-on impacts on physical estuarine characteristics and ecological processes in the impounded area. This study examined the existing physical estuarine characteristics in Swansea Bay and evaluated the risk of eutrophication following tidal power plant operation under ebb-only and two-way strategies using a simple risk assessment model. Two surveys were conducted to measure in-situ temperature, salinity, dissolved oxygen, chlorophyll-a, dissolved inorganic nitrogen and turbidity in the water column at 12 sampling stations selected to cover the location in the tidal energy scheme proposal. The water column was found to be nutrient enriched and essentially vertically homogenous with no strong evidence of stratification. High dissolved oxygen, low turbidity and high phytoplankton biomass indicated by the chlorophyll-a concentrations were observed. The bay did not show any signs of eutrophication as the phytoplankton biomass did not reach the level typical of harmful algal blooms and oxygen depletion was not observed indicating that eutrophication is not currently present in the bay. Based on numerical model predictions, the bay was found to exhibit a moderate response to nutrient enrichment with no risk of eutrophication and no net change in its status following the operation of the lagoon under both ebb-only and two-way operational modes. These findings suggest that the management strategies for protecting water quality in heavily modified estuaries such as Swansea Bay may not need to be altered following the operation of a tidal lagoon. But given the conditions for phytoplankton growth are likely to be more favourable under ebb-only operational mode compared to two-way operational mode, measures that control nutrient inputs to the impounded water column within the lagoon should be considered under the ebb-only operational mode as a prudent precautionary step.

ACS Style

Margaret Kadiri; Holly Zhang; Athanasios Angeloudis; Matthew D. Piggott. Evaluating the eutrophication risk of an artificial tidal lagoon. Ocean & Coastal Management 2021, 203, 105490 .

AMA Style

Margaret Kadiri, Holly Zhang, Athanasios Angeloudis, Matthew D. Piggott. Evaluating the eutrophication risk of an artificial tidal lagoon. Ocean & Coastal Management. 2021; 203 ():105490.

Chicago/Turabian Style

Margaret Kadiri; Holly Zhang; Athanasios Angeloudis; Matthew D. Piggott. 2021. "Evaluating the eutrophication risk of an artificial tidal lagoon." Ocean & Coastal Management 203, no. : 105490.

Journal article
Published: 07 January 2021 in Applied Ocean Research
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Representation of the marine environment is key for reliable coastal hydrodynamic models. This study investigates the implications of common depth-averaged model configuration choices in sufficiently characterising seabed geometry and roughness. In particular, applications requiring a high level of accuracy and/or exhibiting complex flow conditions may call for greater detail in marine environment representation than typically adopted in coastal models. Ramsey Sound, a macrotidal strait in Pembrokeshire, Wales, UK is considered as a case study. The site contains various steeply inclined bathymetric features, including a submerged pinnacle named Horse Rock and a rocky reef called “The Bitches”. The available energy in Ramsey Sound’s tidal currents has attracted attention from tidal energy developers. There is interest in accurately modelling the energetic hydrodynamics surrounding its pronounced bathymetry. The coastal flow solver Thetis is applied to simulate the flow conditions in Ramsey Sound. It is shown that notable prominent bathymetric features in the strait influence localised and, most importantly, regional hydrodynamic characteristics. “The Bitches” consistently accelerate flow in the strait while Horse Rock induces a notable wake structure and flow reversals. The model is calibrated against bed- and vessel-mounted Acoustic Doppler Current Profiler (ADCP) observations, by altering seabed roughness parameterisations. A spatially variable and locally scaled Manning coefficient based on diverse seabed classification observations is found to improve model performance in comparison to uniformly applied constants, the latter a more common approach. The local impact of altering the Manning coefficient configuration is found to be greatest during spring flood periods of high velocity currents. Meanwhile, the effect of coarsening the computational mesh around bathymetric features towards values more typically applied in coastal models is investigated. Results indicate severe misrepresentation of seabed geometry and subsequent wake hydrodynamics unless refined to a mesh element size that adequately represents Horse Rock and “The Bitches”.

ACS Style

Lucas Mackie; Paul S. Evans; Magnus J. Harrold; Tim O`doherty; Matthew D. Piggott; Athanasios Angeloudis. Modelling an energetic tidal strait: investigating implications of common numerical configuration choices. Applied Ocean Research 2021, 108, 102494 .

AMA Style

Lucas Mackie, Paul S. Evans, Magnus J. Harrold, Tim O`doherty, Matthew D. Piggott, Athanasios Angeloudis. Modelling an energetic tidal strait: investigating implications of common numerical configuration choices. Applied Ocean Research. 2021; 108 ():102494.

Chicago/Turabian Style

Lucas Mackie; Paul S. Evans; Magnus J. Harrold; Tim O`doherty; Matthew D. Piggott; Athanasios Angeloudis. 2021. "Modelling an energetic tidal strait: investigating implications of common numerical configuration choices." Applied Ocean Research 108, no. : 102494.

Journal article
Published: 06 October 2020 in Journal of Marine Science and Engineering
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The extraction of tidal energy from head differences represents a predictable and flexible option for generating electricity. Here, we investigate the generation potential of prospective tidal power plants in the UK. Originally conceived as separate projects, operating these schemes as a cooperative system could prove beneficial. Combined with the inherent operational flexibility of tidal range-based schemes, a notable tidal phase difference in selected sites allows for the system to spread power generation over a larger proportion of the day. Using depth-averaged modelling and gradient-based optimisation techniques, we explore how a flexible cumulative operation schedule could be applied to provide a degree of continuous supply if desirable. While fully continuous operation is not achieved, a number of different optimisation schedules deliver cumulative continuous supply for over half of the year. The average minimum cumulative power output on these days is consistently over 500 MW out of a total installed capacity of 6195.3 MW. Furthermore, by introducing financial incentives associated with reliable, baseload supply, we provide an economic assessment of the tidal power plant system. The daily minimum cumulative power output determines income in the modelled idealised baseload market, while excess supply is traded in an hourly variable wholesale energy market. Results indicate that subsidies would be required in order to make a pursuit of continuous generation financially advantageous over energy maximisation strategies.

ACS Style

Lucas Mackie; Daniel Coles; Matthew Piggott; Athanasios Angeloudis. The Potential for Tidal Range Energy Systems to Provide Continuous Power: A UK Case Study. Journal of Marine Science and Engineering 2020, 8, 780 .

AMA Style

Lucas Mackie, Daniel Coles, Matthew Piggott, Athanasios Angeloudis. The Potential for Tidal Range Energy Systems to Provide Continuous Power: A UK Case Study. Journal of Marine Science and Engineering. 2020; 8 (10):780.

Chicago/Turabian Style

Lucas Mackie; Daniel Coles; Matthew Piggott; Athanasios Angeloudis. 2020. "The Potential for Tidal Range Energy Systems to Provide Continuous Power: A UK Case Study." Journal of Marine Science and Engineering 8, no. 10: 780.

Journal article
Published: 12 May 2020 in Ocean & Coastal Management
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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.

ACS Style

Amy L. Baker; Robert M. Craighead; Emma J. Jarvis; Harriett C. Stenton; Athanasios Angeloudis; Lucas Mackie; Alexandros Avdis; Matthew D. Piggott; Jon Hill. Modelling the impact of tidal range energy on species communities. Ocean & Coastal Management 2020, 193, 105221 .

AMA Style

Amy L. Baker, Robert M. Craighead, Emma J. Jarvis, Harriett C. Stenton, Athanasios Angeloudis, Lucas Mackie, Alexandros Avdis, Matthew D. Piggott, Jon Hill. Modelling the impact of tidal range energy on species communities. Ocean & Coastal Management. 2020; 193 ():105221.

Chicago/Turabian Style

Amy L. Baker; Robert M. Craighead; Emma J. Jarvis; Harriett C. Stenton; Athanasios Angeloudis; Lucas Mackie; Alexandros Avdis; Matthew D. Piggott; Jon Hill. 2020. "Modelling the impact of tidal range energy on species communities." Ocean & Coastal Management 193, no. : 105221.

Journal article
Published: 05 April 2020 in Renewable Energy
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Single-basin tidal range power plants have the advantage of predictable energy outputs, but feature non-generation periods in every tidal cycle. Linked-basin tidal power systems can reduce this variability and consistently generate power. However, as a concept the latter are under-studied with limited information on their performance relative to single-basin designs. In addressing this, we outline the basic principles of linked-basin power plant operation and report results from their numerical simulation. Tidal range energy operational models are applied to gauge their capabilities relative to conventional, single-basin tidal power plants. A coastal ocean model (Thetis) is then refined with linked-basin modelling capabilities. Simulations demonstrate that linked-basin systems can reduce non-generation periods at the expense of the extractable energy output relative to conventional tidal lagoons and barrages. As an example, a hypothetical case is considered for a site in the Severn Estuary, UK. The linked-basin system is seen to generate energy 80–100% of the time over a spring-neap cycle, but harnesses at best ≈ 30% of the energy of an equivalent-area single-basin design.

ACS Style

Athanasios Angeloudis; Stephan C. Kramer; Noah Hawkins; Matthew Piggott. On the potential of linked-basin tidal power plants: An operational and coastal modelling assessment. Renewable Energy 2020, 155, 876 -888.

AMA Style

Athanasios Angeloudis, Stephan C. Kramer, Noah Hawkins, Matthew Piggott. On the potential of linked-basin tidal power plants: An operational and coastal modelling assessment. Renewable Energy. 2020; 155 ():876-888.

Chicago/Turabian Style

Athanasios Angeloudis; Stephan C. Kramer; Noah Hawkins; Matthew Piggott. 2020. "On the potential of linked-basin tidal power plants: An operational and coastal modelling assessment." Renewable Energy 155, no. : 876-888.

Journal article
Published: 15 January 2019 in Applied Energy
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Tidal range renewable power plants have the capacity to deliver predictable energy to the electricity grid, subject to the known variability of the tides. Tidal power plants inherently feature advantages that characterise hydro-power more generally, including a lifetime exceeding alternative renewable energy technologies and relatively low Operation & Maintenance costs. Nevertheless, the technology is typically inhibited by the significant upfront investment associated with capital costs. A key aspect that makes the technology stand out relative to other renewable options is the partial flexibility it possesses over the timing of power generation. In this study we provide details on a design methodology targeted at the optimisation of the temporal operation of a tidal range energy structure, specifically the Swansea Bay tidal lagoon that has been proposed within the Bristol Channel, UK. Apart from concentrating on the classical incentive of maximising energy, we formulate an objective functional in a manner that promotes the maximisation of income for the scheme from the Day-Ahead energy market. Simulation results demonstrate that there are opportunities to exploit the predictability of the tides and flexibility over the precise timing of power generation to incur a noticeable reduction in the subsidy costs that are often negotiated with regulators and governments. Additionally, we suggest that this approach should enable tidal range energy to play a more active role in ensuring security of supply in the UK. This is accentuated by the income-based optimisation controls that deliver on average more power over periods when demand is higher. For the Swansea Bay tidal lagoon case study a 23% increase is observed in the income obtained following the optimisation of its operation compared to a non-adaptive operation. Similarly, a 10% increase relative to an energy-maximisation approach over a year’s operation suggests that simply maximising energy generation in a setting where power prices vary may not be an optimal strategy.

ACS Style

Freddie Harcourt; Athanasios Angeloudis; Matthew D. Piggott. Utilising the flexible generation potential of tidal range power plants to optimise economic value. Applied Energy 2019, 237, 873 -884.

AMA Style

Freddie Harcourt, Athanasios Angeloudis, Matthew D. Piggott. Utilising the flexible generation potential of tidal range power plants to optimise economic value. Applied Energy. 2019; 237 ():873-884.

Chicago/Turabian Style

Freddie Harcourt; Athanasios Angeloudis; Matthew D. Piggott. 2019. "Utilising the flexible generation potential of tidal range power plants to optimise economic value." Applied Energy 237, no. : 873-884.

Journal article
Published: 04 January 2019 in Dams and Reservoirs
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The construction and operation of tidal range structures has been in the spotlight since the UK Government-commissioned Hendry Review, published in early 2017, advised that tidal power can play a significant role in the future energy mix. These dam proposals undergo rigorous scrutiny over their feasibility and environmental implications, despite presenting opportunities to deliver sustainable large-scale electricity supplies to the national grid. Preceding efforts to harness the UK's vast untapped tidal energy resource through barrages were dismissed on the grounds of feasibility and environmental uncertainties. There is now a need to develop reliable engineering tools that can be used to improve the feasibility of new designs under consideration. In this case a novel coastal ocean finite element model is coupled with tidal power plant operation algorithms. This is applied to assess the performance of tidal range structures such as the high profile infrastructure projects of the Swansea Bay and Cardiff tidal lagoons. The analysis takes into account an adaptive method of operation that aims to maximise the electricity output over variable spring-neap tidal conditions. It is demonstrated that such hydrodynamic models, when informed regarding the design of the constituent turbines and sluice gates, can simulate the dam's power plant operation to provide insights to the energy output and hydro-environmental impacts of such schemes.

ACS Style

Athanasios Angeloudis. Tidal range structure operation assessment and optimisation. Dams and Reservoirs 2019, 1 -10.

AMA Style

Athanasios Angeloudis. Tidal range structure operation assessment and optimisation. Dams and Reservoirs. 2019; ():1-10.

Chicago/Turabian Style

Athanasios Angeloudis. 2019. "Tidal range structure operation assessment and optimisation." Dams and Reservoirs , no. : 1-10.

Journal article
Published: 01 November 2018 in Renewable Energy
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ACS Style

Simon P. Neill; Athanasios Angeloudis; Peter E. Robins; Ian Walkington; Sophie L. Ward; Ian Masters; Matt J. Lewis; Marco Piano; Alexandros Avdis; Matthew D. Piggott; George Aggidis; Paul Evans; Thomas A.A. Adcock; Audrius Židonis; Reza Ahmadian; Roger Falconer. Tidal range energy resource and optimization – Past perspectives and future challenges. Renewable Energy 2018, 127, 763 -778.

AMA Style

Simon P. Neill, Athanasios Angeloudis, Peter E. Robins, Ian Walkington, Sophie L. Ward, Ian Masters, Matt J. Lewis, Marco Piano, Alexandros Avdis, Matthew D. Piggott, George Aggidis, Paul Evans, Thomas A.A. Adcock, Audrius Židonis, Reza Ahmadian, Roger Falconer. Tidal range energy resource and optimization – Past perspectives and future challenges. Renewable Energy. 2018; 127 ():763-778.

Chicago/Turabian Style

Simon P. Neill; Athanasios Angeloudis; Peter E. Robins; Ian Walkington; Sophie L. Ward; Ian Masters; Matt J. Lewis; Marco Piano; Alexandros Avdis; Matthew D. Piggott; George Aggidis; Paul Evans; Thomas A.A. Adcock; Audrius Židonis; Reza Ahmadian; Roger Falconer. 2018. "Tidal range energy resource and optimization – Past perspectives and future challenges." Renewable Energy 127, no. : 763-778.

Original article
Published: 19 September 2018 in Environmental Fluid Mechanics
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The generation and evolution of tidally-induced vortices in coastal and estuarine regions can influence water quality and sedimentary processes. These effects must be taken into consideration in the development of coastal reservoirs, barrages and lagoons, among other environmental flow applications. Results are presented here on the fate of large-scale vortices within confined tidally-forced domains. A computational approach is employed using the Thetis depth-averaged coastal ocean modeling framework. Initially, two test cases serve to demonstrate model capability in capturing the formation of dipoles downstream of oscillatory flow channels. Diagnostic quantities of vorticity and localized circulation are used to track the 2-D vortex evolution and dissipation. This approach is then applied to tidal lagoon geometries, where flows through the inlet induce a pair of counter rotating vortices (dipoles). Idealized model geometries and inlet conditions are used to determine the impact of three design parameters on large-scale vortical structures: (a) the lagoon geometry aspect ratio in the horizontal plane, (b) the inlet width and (c) the bathymetry profile as the coastline is approached. The dependence of vortex flushing behavior on the dimensionless ratio \({}^{W_\text{i}}\!/_{UT}\) (where \(W_\text{i}\) is the width of the inlet channel, U is the maximum velocity and T is the tidal period) is reaffirmed, while the side walls and the sloping bathymetry are found to affect the vortex dissipation process.

ACS Style

Carolanne V. M. Vouriot; Athanasios Angeloudis; Stephan C. Kramer; Matthew D. Piggott. Fate of large-scale vortices in idealized tidal lagoons. Environmental Fluid Mechanics 2018, 19, 329 -348.

AMA Style

Carolanne V. M. Vouriot, Athanasios Angeloudis, Stephan C. Kramer, Matthew D. Piggott. Fate of large-scale vortices in idealized tidal lagoons. Environmental Fluid Mechanics. 2018; 19 (2):329-348.

Chicago/Turabian Style

Carolanne V. M. Vouriot; Athanasios Angeloudis; Stephan C. Kramer; Matthew D. Piggott. 2018. "Fate of large-scale vortices in idealized tidal lagoons." Environmental Fluid Mechanics 19, no. 2: 329-348.

Journal article
Published: 01 February 2018 in Applied Energy
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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.

ACS Style

Athanasios Angeloudis; Stephan C. Kramer; Alexandros Avdis; Matthew D. Piggott. Optimising tidal range power plant operation. Applied Energy 2018, 212, 680 -690.

AMA Style

Athanasios Angeloudis, Stephan C. Kramer, Alexandros Avdis, Matthew D. Piggott. Optimising tidal range power plant operation. Applied Energy. 2018; 212 ():680-690.

Chicago/Turabian Style

Athanasios Angeloudis; Stephan C. Kramer; Alexandros Avdis; Matthew D. Piggott. 2018. "Optimising tidal range power plant operation." Applied Energy 212, no. : 680-690.

Book chapter
Published: 19 December 2017 in Handbook of Coastal and Ocean Engineering
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Details are given of the growing worldwide interest in tidal renewable energy projects, including tidal stream devices and tidal range structures (i.e. barrages and lagoons), but the main emphasis in this chapter is on tidal range renewable energy structures. In investigating the hydro-environmental impacts of such tidal energy schemes, both for regional and far field effects, a 2D numerical model has been refined to predict the hydrodynamic impacts, including wake effects and flood risk and hazard impacts, and changes in the concentration distribution of conservative and nonconservative solutes, including primarily salinity, turbidity, fecal indicator organisms, and phosphorous and nitrogen levels. The model has been applied to a number of key sites and particularly in the Severn Estuary, UK, which has the second highest tidal range worldwide. The key schemes considered and reported herein include: (i) a series of lagoons along the North Wales coast and (ii) a barrage across the mouth of the Severn Estuary. The main findings are that: (i) two-way generation offers the best options for maintaining the current conditions in the region as closely as possible, (ii) boundary conditions need to be generated from the Continental Shelf, (iii) momentum conservation is crucial for turbine representation, (iv)lagoons interact with one another, reducing efficiency, (v) the design of turbine distribution is critical for optimum efficiency and minimal environmental change.

ACS Style

Roger A. Falconer; Athanasios Angeloudis; Reza Ahmadian; Young C Kim. Modeling Hydro-environmental Impacts of Tidal Range Renewable Energy Projects in Coastal Waters. Handbook of Coastal and Ocean Engineering 2017, 1553 -1574.

AMA Style

Roger A. Falconer, Athanasios Angeloudis, Reza Ahmadian, Young C Kim. Modeling Hydro-environmental Impacts of Tidal Range Renewable Energy Projects in Coastal Waters. Handbook of Coastal and Ocean Engineering. 2017; ():1553-1574.

Chicago/Turabian Style

Roger A. Falconer; Athanasios Angeloudis; Reza Ahmadian; Young C Kim. 2017. "Modeling Hydro-environmental Impacts of Tidal Range Renewable Energy Projects in Coastal Waters." Handbook of Coastal and Ocean Engineering , no. : 1553-1574.

Original article
Published: 18 December 2017 in Environmental Fluid Mechanics
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The results of large-eddy simulations of flow and transient solute transport over a backward facing step and through a 180° bend are presented. The simulations are validated successfully in terms of hydrodynamics and tracer transport with experimental velocity data and measured residence time distribution curves confirming the accuracy of the method. The hydrodynamics are characterised by flow separation and subsequent recirculation in vertical and horizontal directions and the solute dispersion process is a direct response to the significant unsteadiness and turbulence in the flow. The turbulence in the system is analysed and quantified in terms of power density spectra and covariance of velocity fluctuations. The injection of an instantaneous passive tracer and its dispersion through the system is simulated. Large-eddy simulations enable the resolution of the instantaneous flow field and it is demonstrated that the instabilities of intermittent large-scale structures play a distinguished role in the solute transport. The advection and diffusion of the scalar is governed by the severe unsteadiness of the flow and this is visualised and quantified. The analysis of the scalar mass transport budget quantifies the mechanisms controlling the turbulent mixing and reveals that the mass flux is dominated by advection.

ACS Style

P. Ouro; B. Fraga; N. Viti; A. Angeloudis; T. Stoesser; C. Gualtieri. Instantaneous transport of a passive scalar in a turbulent separated flow. Environmental Fluid Mechanics 2017, 18, 487 -513.

AMA Style

P. Ouro, B. Fraga, N. Viti, A. Angeloudis, T. Stoesser, C. Gualtieri. Instantaneous transport of a passive scalar in a turbulent separated flow. Environmental Fluid Mechanics. 2017; 18 (2):487-513.

Chicago/Turabian Style

P. Ouro; B. Fraga; N. Viti; A. Angeloudis; T. Stoesser; C. Gualtieri. 2017. "Instantaneous transport of a passive scalar in a turbulent separated flow." Environmental Fluid Mechanics 18, no. 2: 487-513.

Journal article
Published: 01 December 2017 in Renewable Energy
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The feasibility and sustainable operation of tidal lagoons and barrages has been under scrutiny over uncertainties with regards to their environmental impacts, potential interactions and energy output. A numerical modelling methodology that evaluates their effects on the hydro-environment has been refined to consider technical constraints and specifications associated with variable turbine designs and operational sequences. The method has been employed to assess a number of proposals and their combinations within the Bristol Channel and Severn Estuary in the UK. Operational challenges associated with tidal range power plants are highlighted, while also presenting the capabilities of modelling tools tailored to their assessment. Results indicate that as the project scale increases so does its relative hydrodynamic impact, which may compromise annual energy output expectations if not accounted for. However, the manner in which such projects are operated can also have a significant impact on changing the local hydro-environment, including the ecology and morphology. Therefore, it is imperative that tidal range power plants are designed in such a way that efficiently taps into renewable energy sources, with minimal interference to the regional hydro-environment through their operation

ACS Style

Athanasios Angeloudis; Roger Falconer. Sensitivity of tidal lagoon and barrage hydrodynamic impacts and energy outputs to operational characteristics. Renewable Energy 2017, 114, 337 -351.

AMA Style

Athanasios Angeloudis, Roger Falconer. Sensitivity of tidal lagoon and barrage hydrodynamic impacts and energy outputs to operational characteristics. Renewable Energy. 2017; 114 ():337-351.

Chicago/Turabian Style

Athanasios Angeloudis; Roger Falconer. 2017. "Sensitivity of tidal lagoon and barrage hydrodynamic impacts and energy outputs to operational characteristics." Renewable Energy 114, no. : 337-351.

Journal article
Published: 01 December 2017 in Physics of Fluids
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Large-Eddy Simulations (LESs) and experiments were employed to study the influence of water depth on the hydrodynamics in the wake of a conical island for emergent, shallow, and deeply submerged conditions. The Reynolds numbers based on the island’s base diameter for these conditions range from 6500 to 8125. LES results from the two shallower conditions were validated against experimental measurements from an open channel flume and captured the characteristic flow structures around the cone, including the attached recirculation region, vortex shedding, and separated shear layers. The wake was impacted by the transition from emergent to shallow submerged flow conditions with more subtle changes in time-averaged velocity and instantaneous flow structures when the submergence increases further. Despite differences in the breakdown of the separated shear layers, vortex shedding, and the upward flow region on the leeward face (once the cone’s apex is submerged), similar flow structures to cylinder flow were observed. These include an arch vortex tilted in the downstream direction and von Karman vortices in the far-wake. Spectra of velocity time series and the drag coefficient indicated that the vortex shedding was constrained by the overtopping flow layer, and thus the shedding frequency decreased as the cone’s apex became submerged. Finally, the generalised flow structures in the wake of a submerged conical body are outlined.

ACS Style

Pablo Ouro; Catherine A. M. E. Wilson; Paul Evans; Athanasios Angeloudis. Large-eddy simulation of shallow turbulent wakes behind a conical island. Physics of Fluids 2017, 29, 126601 .

AMA Style

Pablo Ouro, Catherine A. M. E. Wilson, Paul Evans, Athanasios Angeloudis. Large-eddy simulation of shallow turbulent wakes behind a conical island. Physics of Fluids. 2017; 29 (12):126601.

Chicago/Turabian Style

Pablo Ouro; Catherine A. M. E. Wilson; Paul Evans; Athanasios Angeloudis. 2017. "Large-eddy simulation of shallow turbulent wakes behind a conical island." Physics of Fluids 29, no. 12: 126601.

Review
Published: 19 April 2017 in Fluids
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Computational Fluid Dynamics (CFD) has consolidated as a tool to provide understanding and quantitative information regarding many complex environmental flows. The accuracy and reliability of CFD modelling results oftentimes come under scrutiny because of issues in the implementation of and input data for those simulations. Regarding the input data, if an approach based on the Reynolds-Averaged Navier-Stokes (RANS) equations is applied, the turbulent scalar fluxes are generally estimated by assuming the standard gradient diffusion hypothesis (SGDH), which requires the definition of the turbulent Schmidt number, Sct (the ratio of momentum diffusivity to mass diffusivity in the turbulent flow). However, no universally-accepted values of this parameter have been established or, more importantly, methodologies for its computation have been provided. This paper firstly presents a review of previous studies about Sct in environmental flows, involving both water and air systems. Secondly, three case studies are presented where the key role of a correct parameterization of the turbulent Schmidt number is pointed out. These include: (1) transverse mixing in a shallow water flow; (2) tracer transport in a contact tank; and (3) sediment transport in suspension. An overall picture on the use of the Schmidt number in CFD emerges from the paper.

ACS Style

Carlo Gualtieri; Athanasios Angeloudis; Fabian Bombardelli; Sanjeev Jha; Thorsten Stoesser. On the Values for the Turbulent Schmidt Number in Environmental Flows. Fluids 2017, 2, 17 .

AMA Style

Carlo Gualtieri, Athanasios Angeloudis, Fabian Bombardelli, Sanjeev Jha, Thorsten Stoesser. On the Values for the Turbulent Schmidt Number in Environmental Flows. Fluids. 2017; 2 (2):17.

Chicago/Turabian Style

Carlo Gualtieri; Athanasios Angeloudis; Fabian Bombardelli; Sanjeev Jha; Thorsten Stoesser. 2017. "On the Values for the Turbulent Schmidt Number in Environmental Flows." Fluids 2, no. 2: 17.

Journal article
Published: 01 March 2017 in Energy
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The regular and predictable nature of the tide makes the generation of electricity with a tidal lagoon or barrage an attractive form of renewable energy, yet storm surges affect the total water-level. Here, we present the first assessment of the potential impact of storm surges on tidal-range power. Water-level data (2000–2012) at nine UK tide gauges, where tidal-range energy is suitable for development (e.g. Bristol Channel), was used to predict power. Storm surge affected annual resource estimates −5% to +3%, due to inter-annual variability, which is lower than other sources of uncertainty (e.g. lagoon design); therefore, annual resource estimation from astronomical tides alone appears sufficient. However, instantaneous power output was often significantly affected (Normalised Root Mean Squared Error: 3%–8%, Scatter Index: 15%–41%) and so a storm surge prediction system may be required for any future electricity generation scenario that includes large amounts of tidal-range generation. The storm surge influence to tidal-range power varied with the electricity generation strategy considered (flooding tide only, ebb-only or dual; both flood and ebb), but with some spatial and temporal variability. The flood-only strategy was most affected by storm surge, mostly likely because tide-surge interaction increases the chance of higher water-levels on the flooding tide

ACS Style

M.J. Lewis; Athanasios Angeloudis; P.E. Robins; P.S. Evans; S.P. Neill. Influence of storm surge on tidal range energy. Energy 2017, 122, 25 -36.

AMA Style

M.J. Lewis, Athanasios Angeloudis, P.E. Robins, P.S. Evans, S.P. Neill. Influence of storm surge on tidal range energy. Energy. 2017; 122 ():25-36.

Chicago/Turabian Style

M.J. Lewis; Athanasios Angeloudis; P.E. Robins; P.S. Evans; S.P. Neill. 2017. "Influence of storm surge on tidal range energy." Energy 122, no. : 25-36.

Journal article
Published: 01 December 2016 in Renewable Energy
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A methodology associated with the simulation of tidal range energy projects through a coastal hydrodynamic model is discussed regarding its capabilities and limitations. Particular focus is directed towards the formulations imposed for the representation of hydraulic structures and the corresponding model boundary conditions. Details of refinements are presented that would be applicable in representing the flow (and momentum flux) expected through tidal range turbines to inform the regional modelling of tidal lagoons and barrages. A conceptual tidal lagoon along the North Wales coast, a barrage across the Severn Estuary and the Swansea Bay Lagoon proposal are used to demonstrate the effect of the refinements for projects of a different scale. The hydrodynamic model results indicate that boundary refinements, particularly in the form of accurate momentum conservation, have a noticeable influence on near-field conditions and can be critical when assessing the environmental impact arising from the schemes. Finally, it is shown that these models can be used to guide and improve tidal impoundment proposals

ACS Style

Athanasios Angeloudis; Roger Falconer; Samuel Bray; Reza Ahmadian. Representation and operation of tidal energy impoundments in a coastal hydrodynamic model. Renewable Energy 2016, 99, 1103 -1115.

AMA Style

Athanasios Angeloudis, Roger Falconer, Samuel Bray, Reza Ahmadian. Representation and operation of tidal energy impoundments in a coastal hydrodynamic model. Renewable Energy. 2016; 99 ():1103-1115.

Chicago/Turabian Style

Athanasios Angeloudis; Roger Falconer; Samuel Bray; Reza Ahmadian. 2016. "Representation and operation of tidal energy impoundments in a coastal hydrodynamic model." Renewable Energy 99, no. : 1103-1115.