143 results found
Deskos G, Laizet S, Piggott MD, 2019, Turbulence-resolving simulations of wind turbine wakes, RENEWABLE ENERGY, Vol: 134, Pages: 989-1002, ISSN: 0960-1481
Harcourt F, Angeloudis A, Piggott MD, 2019, Utilising the flexible generation potential of tidal range power plants to optimise economic value, APPLIED ENERGY, Vol: 237, Pages: 873-884, ISSN: 0306-2619
Pan W, Kramer SC, Piggott MD, 2019, Multi-layer non-hydrostatic free surface modelling using the discontinuous Galerkin method, OCEAN MODELLING, Vol: 134, Pages: 68-83, ISSN: 1463-5003
Rattia JMN, Percival JR, Neethling SJ, et al., 2018, Modelling local scour near structures with combined mesh movement and mesh optimisation, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 375, Pages: 1220-1237, ISSN: 0021-9991
Deskos G, Piggott MD, 2018, Mesh-adaptive simulations of horizontal-axis turbine arrays using the actuator line method, Publisher: WILEY
Collins DS, Avdis A, Allison PA, 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
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
Karna T, Kramer SC, Mitchell L, et al., 2018, Thetis coastal ocean model: discontinuous Galerkin discretization for the three-dimensional hydrostatic equations, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 11, Pages: 4359-4382, ISSN: 1991-959X
Deskos G, Piggott M, Mesh-adaptive simulations of horizontal-axis turbine arrays using the actuator line method, Wind Energy, ISSN: 1095-4244
Numerical models of the flow and wakes due to turbines operating within a real-scale offshore wind farm can lead to a prohibitively large computational cost, particularly when considering blade-resolved simulations. With the introduction of turbine parametrisations such as the actuator disk (ADM) or the actuator line (ALM) models this problem has been partially addressed, yet the computational cost associated with these simulations remains high. In this work we present an implementation and validation of an ALM within the mesh-adaptive 3D fluid dynamics solver, Fluidity, under a uRANS-based turbulence modelling approach. A key feature of this implementation is the use of mesh optimization techniques which allow for the automatic refinement or coarsening of the mesh locally according to the resolution needed by the fluid flow solver. The model is first validated against experimental data from wind tunnel tests. Finally, we demonstrate the benefits of mesh-adaptivity by considering flow past the Lillgrund offshore wind farm.
Piggott MD, Optimisation of tidal stream turbine arrays within the Alderney Race, European Wave and Tidal Energy Conference
Avdis A, Candy AS, Hill J, et al., 2018, Efficient unstructured mesh generation for marine renewable energy applications, RENEWABLE ENERGY, Vol: 116, Pages: 842-856, ISSN: 0960-1481
Vouriot CVM, Angeloudis A, Kramer SC, et al., 2018, Fate of large-scale vortices in idealized tidal lagoons, Environmental Fluid Mechanics, ISSN: 1567-7419
© 2018, The Author(s). 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 Wi/UT (where Wi 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.
van Sebille E, Griffies SM, Abernathey R, et al., 2018, Lagrangian ocean analysis: Fundamentals and practices, OCEAN MODELLING, Vol: 121, Pages: 49-75, ISSN: 1463-5003
Piggott MD, Comparison of 0-D, 1-D and 2-D model capabilities for tidal range energy resource assessments, European Wave and Tidal Energy Conference
Culley DM, Funke SW, Kramer SC, et al., 2017, A surrogate-model assisted approach for optimising the size of tidal turbine arrays, International Journal of Marine Energy, Vol: 19, Pages: 357-373, ISSN: 2214-1669
© 2017 The Authors. The new and costly nature of tidal stream energy extraction technologies can lead to narrow margins of success for a project. The design process is thus a delicate balancing act - to maximise the energy extracted, while minimising cost and risk. Scenario specific factors, such as site characteristics, technological constraints and practical engineering considerations greatly impact upon both the appropriate number of turbines to include within a tidal current turbine array (array size), and the individual locations of those turbines (turbine micro-siting). Both have been shown to significantly impact upon the energy yield and profitability of an array. The micro-siting arrangement for a given number of turbines can significantly influence the power extraction of a tidal farm. Until the layout has been optimised (a process which may incorporate turbine parameters, local bathymetry and a host of other practical, physical, legal, financial or environmental constraints) an accurate forecast of the yield of that array cannot be determined. This process can be thought of as 'tuning' an array to the proposed site to maximise desirable outcomes and mitigate undesirable effects. The influence of micro-siting on the farm performance means that determining the optimal array size needs to be coupled to the micro-siting process. In particular, the micro-siting needs to be repeated for any new trial array size in order to be able to compare the performance of the different farm sizes. Considering the large number of design variables in the micro-siting problem (which includes at least the positions of each turbine) it becomes clear that algorithmic optimisation is a key tool to rigorously determine the optimal array size and layout. This paper proposes a nested optimisation approach for solving the array size and layout problem. The core of this approach consists of two nested optimisation procedures. The 'outer' optimisation determines the array size. At
Schwedes T, Ham DA, Funke SW, et al., 2017, Mesh dependence in PDE-constrained optimisation an application in tidal turbine array layouts, Publisher: Springer, ISBN: 9783319594835
This section verifies the iteration count estimates by solving the optimisation problem (2.2) numerically. The first experiment investigates the number of optimisation iterations required to solve (2.2) under non-uniform mesh refinement.
Funke SW, Farrell PE, Piggott MD, 2017, Reconstructing wave profiles from inundation data, COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING, Vol: 322, Pages: 167-186, ISSN: 0045-7825
du Feu RJ, Funke SW, Kramer SC, et al., 2017, The trade-off between tidal-turbine array yield and impact on flow: A multi-objective optimisation problem, Renewable Energy, Vol: 114, Pages: 1247-1257, ISSN: 1879-0682
This paper introduces a new approach for investigating trade-offs between different societal objectives in the design of tidal-turbine arrays. This method is demonstrated through the trade-off between the yield of an array, and the extent to which that array alters the flow. This is posed as a multi-objective optimisation problem, and the problem is investigated using the array layout optimisation tool OpenTidalFarm. Motivated by environmental concerns, OpenTidalFarm is adapted to not only maximise array yield but also to minimise the effect of the array upon the hydrodynamics of the region, specifically the flow velocity. A linear scalarisation of the multi-objective optimisation problem is solved for a series of different weightings of the two conflicting objectives. Two idealised test scenarios are evaluated and in each case a set of Pareto solutions is found. These arrays are assessed for the power they generate and the severity of change they cause in the flow velocity. These analyses allow for the identification of trade-offs between these two objectives, while the methods proposed can similarly be applied to the two key societal objectives of energy production and conservation, thus providing information that could be valuable to stakeholders and policymakers when making decisions on array design.
Deskos G, Abolghasemi AA, Piggott MD, Wake predictions from two turbine parametrisation models using mesh-optimisation techniques, European Wave and Tidal Energy Conference, ISSN: 2309-1983
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
Parkinson SD, Funke SW, Hill J, et al., 2017, Application of the adjoint approach to optimise the initial conditions of a turbidity current with the AdjointTurbidity 1.0 model, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 10, Pages: 1051-1068, ISSN: 1991-959X
Smith R, 2017, Numerical modelling of tsunami generated by deformable submarine slides
Submarine slides can generate tsunami waves that cause significant damage and loss of life. Numerical modelling of submarine slide generated waves is complex and computationally challenging, but is useful to understand the nature of the waves that are generated, and identify the important factors in determining wave characteristics which in turn are used in risk assessments. In this work, the open-source, finite-element, unstructured mesh fluid dynamics framework Fluidity is used to simulate submarine slide tsunami using a number of different numerical approaches. First, three alternative approaches for simulating submarine slide acceleration, deformation and wave generation with full coupling between the slide and water in two dimensions are compared. Each approach is verified against benchmarks from experimental and other numerical studies, at different scales, for deformable submarine slides. There is good agreement to both laboratory results and other numerical models, both with a fixed mesh and a dynamically adaptive mesh, tracking important features of the slide geometry as the simulation progresses. Second, Fluidity is also used in a single-layer Bousinesq approximation in conjunction with a prescribed velocity boundary condition to model the propagation of slide tsunami in two and three dimensions. A new, efficient approach for submarine slide tsunami that accounts for slide dynamics and deformation is developed by imposing slide dynamics, derived from multi-material simulations. Two submarine slides are simulated in the Atlantic Ocean, and these generate waves up to 10 m high at the coast of the British Isles. Results indicate the largest waves are generated in the direction of slide motion. The lowest waves are generated perpendicular to the slide motion. The slide velocity and acceleration are the most important factors in determining wave height. Slides that deform generate higher waves than rigid slides, although this effect is of secondary importance f
Funke SW, Kramer SC, Piggott MD, 2016, Design optimisation and resource assessment for tidal-stream renewable energy farms using a new continuous turbine approach, Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Abolghasemi MA, Piggott MD, Spinneken J, et al., 2016, Simulating tidal turbines with multi-scale mesh optimisation techniques, JOURNAL OF FLUIDS AND STRUCTURES, Vol: 66, Pages: 69-90, ISSN: 0889-9746
Funke SW, Kramer SC, Piggott MD, Design optimisation and resource assessment for tidal-stream renewable energy farms using a new continuous turbine approach, Renewable Energy, ISSN: 1879-0682
This paper presents a new approach for optimising the design of tidal stream turbine farms. In this approach, the turbine farm is represented by a turbine density function that specifies the number of turbines per unit area and an associated continuous locally-enhanced bottom friction field. The farm design question is formulated as a mathematical optimisation problem constrained by the shallow water equations and solved with efficient, gradient-based optimisation methods. The resulting method is accurate, computationally efficient, allows complex installation constraints, and supports different goal quantities such as to maximise power or profit. The outputs of the optimisation are the optimal number of turbines, their location within the farm, the overall farm profit, the farm's power extraction, and the installation cost.We demonstrate the capabilities of the method on a validated numerical model of the Pentland Firth, Scotland. We optimise the design of four tidal farms simultaneously, as well as individually, and study how farms in close proximity may impact upon one another.
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)
Kramer SC, Piggott MD, 2016, A correction to the enhanced bottom drag parameterisation of tidal turbines, RENEWABLE ENERGY, Vol: 92, Pages: 385-396, ISSN: 0960-1481
Nunez Rattia JM, Percival JR, Yeager B, et al., 2016, Numerical simulation of scour below pipelines using flexible mesh methods, The 8th International Conference on Scour and Erosion, Pages: 101-108
Evaluating bed morphological structure and evolution (specifically the scoured bed level) accurately using numerical models is critical for analyses of the stability of many marine structures. This paper discusses the performance of an implementation within Fluidity, an open source, general purpose, Computational Fluid Dynamics (CFD) code, capable of handling arbitrary multi-scale unstructured tetrahedral meshes and including algorithms to perform dynamic anisotropic mesh adaptivity. The flexibility over mesh structure and resolution that these capabilities provide makes it potentially highly suitable for coupling the structural scale with larger scale ocean dynamics. In this very preliminary study the solver approach is demonstrated for an idealised scenario. Discontinuous Galerkin finite-element (DG-FEM) based discretisation methods have been used for the hydrodynamics and morphological calculations, and automatic mesh deformation has been utilised to account for bed evolution changes while preserving the validity and quality of the mesh. In future work, the solver will be used in three-dimensional impinging jet and other industrial and environmental scour studies.
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