The global cost of corrosion-related damage is estimated to be £1.9tn annually (3.4% of GDP) and corrosion costs the UK ~£80bn per annum. Hydrogen-associated stress corrosion embrittlement is an important class of environmental degradation. Titanium alloys were until the late 60s considered immune to stress corrosion embrittlement by reacting with water vapour, but subsequent experience has falsified this hypothesis. Therefore, substantial industrial and safety benefit to the UK can be obtained if H-associated degradation in Ti alloys can be understood and mitigated by material design. Because of its ubiquity in the world, hydrogen related cracking is a grand challenge in materials science; from ceramics to perovskite solar cells H-associated degradation mechanisms are critical to the in-service viability of many materials, including metals. Our strategy will be to provide H-tolerance to a material, either by limiting the ingress of embrittling species or by providing traps within the material, where such species can be somehow deactivated. Hydrogen is highly mobile and therefore can concentrate and embrittle critical micro- and nano-scopic features in materials, this can happen over the course of minutes or hours. A main challenge however has been the detection of H inside metallic systems. Lacking an electron shell to excite, H cannot be measured in electron microscopy and vacuum systems often contain H, and so even mass spectrometry techniques struggle to sensitively measure H in a sample. Therefore, our understanding of how hydrogen leads to cracking in different materials systems is much more limited than we might like to concede. We will develop new methods for atomic-scale experimental measurements to identify where Hydrogen locates within a material. Small samples will be prepared and handled at cryogenic temperatures to limit H mobility and elemental "atom-by-atom" mapping will be conducted to understand how the mobility of H changes by trapping at different material phases, interfaces and crystal defects. Some Ti alloys are more resistant to Hydrogen embrittlement and corrosion than others, but the physical mechanisms behind are not well understood. For instance, highly pure titanium is nearly immune to H, but its corrosion performance drastically changes if small impurities are present; some elements, such as Fe, are known to reduce corrosion performance, whereas others, including Mo and Pd, dramatically improve corrosion. We will then carefully examine the effect of typical alloy additions on the cracking propensity using bend tests under H exposure in alloys with different compositions. Detailed microscopic inspection at several length-scales will be conducted to understand the mechanisms of H-induced failure. The prediction of H mobility and H-related damage in engineering alloys is complicated, as these materials contain several phases, crystal defects and alloying elements, which all influence H behaviour. With so many interacting effects, the use of physically-faithful models and simulations will be vital to disentangling them fully from each other. Therefore, we will develop new computational models for hydrogen diffusion within a material to elucidate how different features affect local H transport and trapping. In addition, we will adopt and improve micro-mechanics modelling techniques, via incorporating equations for the newly-unravelled embrittlement mechanisms in Ti, and compare the mechanical performance of H-containing alloys against their H-free version. Based on these outcomes, we will develop optimal material guidelines for the alloy and process designer, highlighting what phase/alloy combinations are more resistant against H-induced failure. In addition, optimal materials will be designed, manufactured and tested in order to provide final validation of our concepts.

Energy demand will be up by more than a quarter by 2040 [International Energy Agency data]. Given the dominance of combustion in meeting this demand, it is imperative to develop low-carbon, efficient gas turbine (GT) engines to reduce emissions impact and tackle the global warming as set by the Paris Agreement. In recent years lean premixed technology has attracted interest due to its potential of reduced emissions and high efficiency. However, lean combustion is prone to instabilities that may lead to unwanted oscillations, flame extinctions and flashbacks. Use of low or zero-carbon fuels like hydrogen is also limited because the high speeds needed to prevent flashbacks due the high low-heating values (LHV) can destabilise the vortex dynamics. Further development is thus required to achieve better efficiency and lower emissions, and effective flame holding techniques are crucial for this development. In ultra-compact combustor design, trapped vortex (TV) systems are implemented either in the primary zone or in the inter-turbine region to increase the resident time of combusting gases, resulting in better mixing, thus higher efficiency and lower emissions. Higher resident times also imply a shorter combustor, thus a lighter engine and less fuel consumption, also helping the process of hybridisation in multi-cycle devices. TV are locked stably within a cavity and thus are less sensitive to external disturbances even at high speeds, allowing use of low or zero-carbon fuels with high LHV like hydrogen. However, the process of flame stabilisation is rather complex because of the shear and boundary layer (BL) vortex dynamics, the strong heat transfer to the wall and the simultaneous occurrence of flame propagation and auto-ignition processes. The effective control of the flame dynamics requires a deep understanding of these processes. This project aims to develop improved understanding of the fundamental processes governing flame stabilisation in TV systems for ultra-compact combustion design, and their potential to deliver improved flame stability and low emissions at high speed (subsonic) conditions in the context of lean premixed technology. In particular, the TV physics will be studied i) in presence of a radially accelerating flow representing the swirled flow dynamics at the entrance of the combustion chamber; and ii) in presence of an axially accelerating flow when the cavity is located within the converging duct near the combustor exit. Both swirled and axial acceleration can destabilise the vortex dynamics, so this dynamics has to be understood before TV systems can be effectively employed. The analyses will be conducted through high-fidelity large eddy simulations (LES), which represents a cost-effective tool as compared to expensive experimental investigations. In this way the effect of turbulence, equivalence ratio and cavity geometry can be explored in details via parametric study. Moreover, the performance of different alternative fuels and their implication in terms of flame holding and model performance can be evaluated for different TV designs. An improved model involving presumed PDF approaches based on mixed flamelets/perfectly stirred reactor will be developed to account for the aforementioned physics. The fundamental understanding for this development will be extracted from unprecedented detailed direct numerical simulation (DNS) and by using validation data from experiments provided by the project partners. The outcomes of this project will significantly help the development of modern, low-carbon engines, and improve the understanding of the fundamental physics within these devices. Moreover, the project will lead to the development of CFD codes and models that can be used in industrial design cycles. Thus, this project is timely and strongly relevant for leading UK industries such as Rolls-Royce and other emerging industry, and will help them to maintain their leading role in the power-generation sector.

The biggest scientific and engineering challenges often lie in between disciplines. Through the years, we have gained a good understanding of how materials behave when subjected to mechanical loads (solid mechanics). We also understand the nature of the chemical reactions occurring when materials are exposed to a given environment (electrochemistry). However, predicting material behaviour due to combined exposure to mechanical loads and a degrading environment continues to be an elusive goal. Not being able to understand and predict electro-chemo-mechanics phenomena comes at a great cost since materials are very sensitive to environmental and mechanical degradation in many applications. The value of the fundamental science conducted in this fellowship will be demonstrated on two of these applications: (1) corrosion damage, and (2) Li-Ion batteries. Their importance cannot be emphasised enough. Solely in the UK, failure of structures and industrial components due to corrosion entails a staggering cost of £46 billion per annum. Li-Ion batteries are key enablers in achieving universal access to reliable, clean, sustainable energy. Now, there is an opportunity to develop models that can prevent corrosion failures and significantly enhance progress in battery technology. Larger computer resources and new algorithms enable simulating concurrent (coupled) physical processes such as chemical reactions, diffusion of species and mechanical deformation; so-called multi-physics modelling. However, the opportunity of building upon the success of multi-physics simulations to predict material degradation is held back due to our inability to model how the boundary between two different phases develops over time. For example, corrosion is often non-uniform, leading to small defects (pits) that grow and act as crack initiators. Preventing the associated catastrophic failures, such as the Morandi Bridge collapse, requires capturing how these defects will nucleate at the electrolyte-material interface and grow. But the modelling of morphological changes in an evolving interface has been long considered a mathematical and computational challenge. I will overcome this longstanding obstacle by smearing the "sharp" interface over a small diffuse region using an auxiliary "phase field" variable - a paradigm change that will make tracking of evolving interfaces amenable to numerical computations. A new generation of models will be developed and validated with powerful 3D techniques such as X-ray Computed Tomography, which have timely experienced notable improvements in spatial resolution and image reconstruction times. By explicitly capturing the damage process, this fellowship will not only open new horizons in the understanding of multi-physics material degradation phenomena but also set the basis for the introduction of simulation-based assessment in engineering practice; model predictions can be compared with inspection data, introducing the "Digital Twins" and "Virtual Testing" paradigms into engineering applications involving demanding environments. The near-term societal impact will be demonstrated by addressing salient technological problems in offshore energy, batteries, water supply networks and nuclear fission. Efforts will be guided by the fellowship advisory board, which includes leading firms in each of these sectors: EDF Energy, Rolls-Royce, SUEZ, PA Consulting, Vattenfall and Subsea7. For example, the new generation of models developed will be used to assist in the life extension decision of the oldest large-scale wind farm in the world, Horns Rev 1. The lessons learned in this world-first engineering assessment will set an example for the entire sector and demonstrate the potential of computer simulations in enhancing the economic viability of the leading renewable energy source. The successful fellowship will lay scientific foundations for new engineering solutions that will improve UK's competitiveness and our quality of life.

My fellowship aims to develop expertise in the area of boiling and nuclear thermal hydraulics research via the development of novel analytical and computational techniques, the generation of new experimental data and their application to model the behaviour of boiling fluids in industrial systems. The behaviour of fluids, such as water, used in industrial processes and power generation, is to a large extent governed by the interaction of bubbles and droplets with solid surfaces. These are found in heat exchangers, boilers and condensers and are integral part of the operation of nuclear reactors, which relies on the boiling of water at solid surfaces. Altering the physical and chemical properties of industrial surfaces enables controlling heat and mass transfer in fluid processes such as boiling flows, greatly increasing their potential as coolants. Surface modification could then be used to develop bespoke surfaces to enhance heat transfer in the core and in cooling systems of nuclear reactors. Development of such a technology requires a sound physical understanding of surface effects in fluids through theoretical analysis and numerical modelling. During my fellowship I will develop fundamental modelling techniques to study the surface-dependent behaviour of fluid processes found in nuclear thermal hydraulics applications. The radically new methodologies required to enable this technological inventive step will be developed via collaboration with world leading experts and state-of-the-art facilities found within the Thermofluids, Tribology and Nuclear Engineering Groups of the Mechanical Engineering Department at Imperial College London, enriching the development of computational models of fluid processes with insight from new experiments and simulation at the molecular scale. Collaboration with project partners Rolls-Royce and Hexxcell will ensure direct industrial application of methods and capabilities generated during my fellowship (see the accompanying Project Partner Statements of Support). In-depth knowledge of the influence of surface effects on nuclear reactor thermal hydraulics is crucial to the operation of the current fleet of water-cooled reactors and is required for the design and safety certification of new' Generation III+' plants planned to be constructed in the UK, as well as for the assessment of future reactor concepts. Some of these, such as the Advanced Modular Reactor, are at the core of scoping studies by the government. The knowledge and capabilities generated by this fellowship will provide the civil service, such as the Department of Energy & Climate Change (DECC), now part of the Department for Business, Energy & Industrial Strategy (BEIS), with a solid scientific foundation for the UK civil nuclear energy policy. Outside of the nuclear sector, stakeholders will benefit from industrial exploitation of the new, more capable modelling techniques proposed in the course of my fellowship. The work will have wide application to the design of industrial processes that use, for example, boilers, condensers, heat pipes and cooling systems. These are increasingly relying on the use of Computational Fluid Dynamics simulation (CFD) for their design. Developers of CFD software will benefit from the newly developed physical modelling capabilities delivered by my fellowship and will be able to implement the new simulation approaches into their commercial software packages.

My fellowship aims to develop expertise in the area of boiling and nuclear thermal hydraulics research via the development of novel analytical and computational techniques, the generation of new experimental data and their application to model the behaviour of boiling fluids in industrial systems. The behaviour of fluids, such as water, used in industrial processes and power generation, is to a large extent governed by the interaction of bubbles and droplets with solid surfaces. These are found in heat exchangers, boilers and condensers and are integral part of the operation of nuclear reactors, which relies on the boiling of water at solid surfaces. Altering the physical and chemical properties of industrial surfaces enables controlling heat and mass transfer in fluid processes such as boiling flows, greatly increasing their potential as coolants. Surface modification could then be used to develop bespoke surfaces to enhance heat transfer in the core and in cooling systems of nuclear reactors. Development of such a technology requires a sound physical understanding of surface effects in fluids through theoretical analysis and numerical modelling. During my fellowship I will develop fundamental modelling techniques to study the surface-dependent behaviour of fluid processes found in nuclear thermal hydraulics applications. The radically new methodologies required to enable this technological inventive step will be developed via collaboration with world leading experts and state-of-the-art facilities found within the Thermofluids, Tribology and Nuclear Engineering Groups of the Mechanical Engineering Department at Imperial College London, enriching the development of computational models of fluid processes with insight from new experiments and simulation at the molecular scale. Collaboration with project partners Rolls-Royce and Hexxcell will ensure direct industrial application of methods and capabilities generated during my fellowship (see the accompanying Project Partner Statements of Support). In-depth knowledge of the influence of surface effects on nuclear reactor thermal hydraulics is crucial to the operation of the current fleet of water-cooled reactors and is required for the design and safety certification of new' Generation III+' plants planned to be constructed in the UK, as well as for the assessment of future reactor concepts. Some of these, such as the Advanced Modular Reactor, are at the core of scoping studies by the government. The knowledge and capabilities generated by this fellowship will provide the civil service, such as the Department of Energy & Climate Change (DECC), now part of the Department for Business, Energy & Industrial Strategy (BEIS), with a solid scientific foundation for the UK civil nuclear energy policy. Outside of the nuclear sector, stakeholders will benefit from industrial exploitation of the new, more capable modelling techniques proposed in the course of my fellowship. The work will have wide application to the design of industrial processes that use, for example, boilers, condensers, heat pipes and cooling systems. These are increasingly relying on the use of Computational Fluid Dynamics simulation (CFD) for their design. Developers of CFD software will benefit from the newly developed physical modelling capabilities delivered by my fellowship and will be able to implement the new simulation approaches into their commercial software packages.