Among technically and economically viable renewable energy sources, wind power is that which exploitation has been growing fastest in the recent years. This research focuses on modern Horizontal Axis Wind Turbines (HAWT's), which typically feature two- or three-blade rotors. The span of HAWT blades can vary from a few meters to more than 100 meters, and their design is a complex multidisciplinary task which requires consideration of strong unsteady interactions of aerodynamic and structural forces. Some of the most dangerous sources of aerodynamic unsteadiness are a) yawed wind, due to temporary non-orthogonality of wind and rotor plane, and b) blade dynamic stall. These phenomena result in the blades experiencing time-varying aerodynamic forces, which can excite undesired structural vibrations. This occurrence, in turn, can dramatically reduce the fatigue life of the blades and their supporting structure, yielding premature mechanical failures. Events of this kind can compromise the technical and financial success of the installation, which heavily relies on fulfilling the expectations of minimal servicing on time-scales of the order of 10 to 30 years. These facts highlight the importance of the aeroelastic design process of HAWT blades. The unsteady aerodynamic loads required to determine the structural response must be understood and accurately quantified in the development phase of the turbine. Due to the sizes at stake, in most cases it is infeasible to perform aeroelastic testing, not only from an economic but also logistic viewpoint. Hence these aeroelastic issues can only be tackled by using accurate simulation tools.The general motivation of this project is two-fold: it aims both at enriching the knowledge of unsteady flows relevant to wind turbine aeroelasticity, and advancing the state-of-the-art of the computational technology to accomplish this task. These objectives are pursued by using a novel Computational Fluid Dynamics (CFD) approach to wind turbine unsteady aerodynamics. The unsteady periodic flow relevant to aeroelastic analyses is determined by solving the three-dimensional unsteady viscous flow equations with the nonlinear frequency-domain (NLFD) technology. The NLFD-CFD approach has been successfully applied to fixed-wing and turbomachinery aeroelasticity. This research will exploit this high-fidelity methodology to enhance the understanding of the severe unsteady aerodynamic forcing of HAWT blades, and substantially reduce computational costs with respect to conventional time-domain CFD analyses. This method is particularly well suited to investigate the unsteady aerodynamic blade loads associated with stall-induced vibrations and yawed wind. On the other hand, this technology will greatly help designers to develop new blades without relying on the database of existing airfoil data on which the majority of present analysis and design systems depend. One of the main results of this project will be to greatly reduce the dichotomy between the conflicting requirements of physical accuracy and computational affordability of the three-dimensional unsteady viscous flow models for wind turbine unsteady aerodynamics and aeroelasticity. The achievements of this research will benefit the British and European industry in that they will offer an effective tool to design more efficient and reliable blades. The NLFD-CFD technology will also provide deeper insight into unsteady aerodynamic phenomena which affect the fatigue life of wind turbines. In the next few years, the certification process of wind turbines will enforce stricter requirements on the industry. The developed technology will support the analyses required to meet enhanced certification standards. The Unsteady Aerodynamics Research Community as a whole will also benefit from this research, because its findings will enhance and consolidate the deployment of the NLFD technology in rotorcraft, turbomachinery, and aircraft aeroelasticity.

Any structure exposed to breaking waves, be it a simple breakwater or a complex and expensive marine energy machine, will be exposed to high wave impact loads as overturning wave crests slam into it. The violence of the motion of the water surface as waves break are well-known to surfers who seek out such conditions. Marine renewable energy devices will be hit by the most violent storms that nature can produce, yet they are required to produce significant power when the weather is benign and the waves relatively small. This dichotomy can result in expensive failures such as that of the Osprey, a 2MW wave power prototype device located off the north coast of Scotland, which was damaged and sank in a storm. If marine renewable energy is to play a significant role in meeting the energy requirements of the the United Kingdom, all energy extraction devices must survive for many years and many large storms without damage. Hence accurate design methods are required to estimate the peak hydrodynamic loads occurring in such storms. This project explores the science and engineering required to ensure that renewable energy devices survive extreme conditions, and seeks to identify the upper limit of device operations in less severe conditions. Key to making a significant advance in survivability is understanding how steep and violent waves behave on significant currents. Both wave power machines and marine current turbines are likely to be located in relatively shallow water with relatively fast tidal currents, obviously for tidal turbines this is a virtue! If the current is fast and the water shallow, there will be considerable resistance to the flow close to the sea-bed and less further up towards the surface. Thus, the current is likely to be highly sheared and very turbulent. Add on top of this bulk flow violently overturning steep waves and it is clear that the water will be moving around very fast in local regions. The first part of this project is to characterize the statistics of waves and how this varies over time for decades to decades. Next the waves are combined with sheared currents. Then models of marine renewable energy devices will be exposed to such violent combined wave and current events and the forces measured. Finally we aim to develop and test force computer based computational methods for assessing loads. The overall output from this research project will make an important contribution to removing blocks limiting and slowing down the large-scale implementation of marine renewable energy.

The EU has a binding target of 20% of energy to come from renewables by 2020, with an associated CO2 emissions reduction target of 20% (relative to 1990) and a 20% reduction on energy usage by the same date. This is the so-called 20/20/20 target. The UK's target is for 15% of energy to be sourced from renewables by this date. For this target to be met, over 30% of electricity will need to be generated from renewables and it is anticipated that 31GW of this will come from wind power with 13GW onshore and 18GW offshore by 2020 to 40GW of offshore wind power capacity could be installed by 2030. At present 6GW of wind power have been installed onshore and 3GW offshore. Because of environmental concerns, the development of onshore wind power in the UK is being constrained making the cost-effective and reliable offshore development ever more important. To increase offshore capacity by at least a factor of five in seven years, whilst minimising the cost of energy, presents very significant design, operational and logistical challenges. Within the above context and in the longer term, wind farms and wind turbines will be sited further offshore in deeper water and become bigger. The proposed Supergen Wind Hub brings together leading wind energy academic research groups in UK to address the medium term challenges of scaling up to multiple wind farms, considering how to better build, operate and maintain multi-GW arrays of wind turbines whilst providing a reliable source of electricity whose characteristics can be effectively integrated into a modern power system such as that in the UK. The wind resource over both short and long terms, the interaction of wakes within a wind farm and the turbine loads and their impact on reliability will all need to be better understood. The layout of the farms, including foundations, impact on radar and power systems and shore-connection issues, will need to be optimised. The most effective and efficient operation of wind farms will require them to act as virtual conventional power plants flexibly responding to the current conditions, the wind turbines' state and operational demands and grid-integration requirements. The programme of research for the Supergen Wind Energy Hub will focus on all of the above, both at the level of single farms and of clusters of farms.

The Lancaster Centre for Doctoral Training in Statistics and Operational Research (STOR) will meet the current critical need to address the national skills shortage within both disciplines. These complementary areas of mathematics underpin a wide-range of industries including defence, healthcare, finance, energy and transport. Thus, the development of this integrated, industrially-focused doctoral training centre is key for national competitiveness. Combined with the input of our industrial partners, the formation of the centre will provide a research training environment focused on methodological research motivated and applied to important real scientific/industrial applications. The centre will be designed to attract, train and nurture the analytic research capacity of the UK's strongest numerate graduates, thus developing a generation of doctoral scientists capable of applying their research skills to industrial applications through either academic or industrial career paths. Key aims of centre are:(i) to increase national doctoral recruitment into STOR through a programme attractive to substantial numbers of students outside those who would normally consider doctoral study in the area; (ii) to train graduates capable of producing research of high quality and with major industrial and scientific impact;(iii) to produce highly employable graduates equipped with the broad skills needed for rapid career progression in academia or industry;(iv) to stimulate research at the interface of STOR through doctoral projects which span the disciplines. The long-term vision for this centre is that it will grow into a national centre of excellence for a collaborative doctoral training environment in STOR between academia and industry, leading to a sustainable model for better exploitation of research.

The primary aim of the project is the assessment of the extreme wave loads on WECs using numerical models validated against experimental observations and full-scale prototype data. The project team combines institutions with significant experience in research into extreme waves (Imperial College), wave energy converters (Queen's University Belfast) and numerical modelling (Manchester Metropolitan University), forming a strong and well-balanced consortium. They will be supported by a steering committee comprising a number of key industrial practitioners and stakeholders, bringing in a wide range of backgrounds from device developers, certifying bodies and the offshore industry. In designing wave energy converters (WECs), scientists and engineers face the challenge of having to compromise between two competing criteria. The power take-off, with all associated mechanical and electrical components having to be optimised for an annual average or nominal sea state. At the same time all these components will have to withstand large storm events, where the applied fluid loads are substantially higher compared to the nominal sea state. A successful design is inevitably characterised by one that balances these two criteria. Identifying such a balance at an early design stage (prior to expensive small or large scale physical model testing) requires accurate, reliable and efficient numerical models appropriate to both design criteria. Survivability defines the long term success of a WEC, and must be addressed by design. Water waves exhibit inherent nonlinearities, which are functions of the wave steepness. In severe sea states, linear models fail to predict the fluid kinematics. As a result, the numerical modelling of wave loading in severe sea states is challenging; the loads being directly affected by the underlying fluid kinematics. Further, the occurrences of wave impacts, wave breaking and air entrainment pose additional challenges. An accurate description of wave nonlinearities, combined with the ability to model local loading effects, is key to the success of the numerical modelling. The project team brings in world-leading expertise in the development of numerical models. In fact, these models have now reached a level of sophistication where a direct comparison with experimental data is practical. The integrated research programme builds upon (i) The latest advances in Met-Ocean, providing a realistic input to both the numerical and the experimental modelling (ii) Numerical modelling based on a hierarchical approach, ranging from linear and fully nonlinear potential flow models to fully nonlinear viscous flow solvers (iii) Extensive experimental investigation using state-of-the-art wave testing facilities appropriate to both shallow and intermediate / deep water conditions (iv) Comparisons with field data relating to loading of prototype WECs The results of the numerical models will be analysed to provide guidance on the appropriateness of particular models, as well as issues associated with the scaling of extreme loads. This will enable an estimation of the uncertainty in extreme loads based on the modelling technique adopted. The research programme initially focuses on two generic device types, and guidelines for the application of the models to other WECs will be developed. In summary, the project is defined by a twin-track approach, combining advanced numerical models and careful experimental practice; the results of which will help to facilitate the large-scale deployment of wave energy converters.