The efficiency and performance of an aerodynamic surface (wind turbine blade or a ship rudder) is a trade-off between the lift generated and the drag incurred by it. The required lift force is attained by changing the shape and orientation of the geometry, which generates a pressure and load distribution along its length. The drag incurred depends on the characteristics of the turbulent boundary layer flow that develops over the surface. Unfortunately, these two design requirements are not independent of each other as the turbulent boundary layer depends on the overlying non-zero pressure gradient due to the pressure distribution. Additionally, the boundary layer flow also depends on the topographical features (or roughness) of the surface where features as small as 10 microns are considered to be hydrodynamically "rough". This situation where the boundary layer flow is under the influence of both non-zero pressure gradient and surface roughness is pervasive in engineering and environmental applications. Examples include flow over airfoils/turbine blades, ducts, flow over/around buildings, hills/valleys etc. Despite its prevalence, the effects of pressure gradient on flow over rough surfaces remains largely unexplored. As we strive towards net zero carbon emissions by 2050, it is timely to develop new understanding and modelling strategies that capture the influence of pressure gradients on the performance of flow over rough surfaces. In this project, we aim to characterise the evolution of non-zero pressure gradient (PG) turbulent boundary layers (TBL) over rough surfaces and thereby identify the parameters that dictate the response of boundary layers to streamwise pressure gradients. A comprehensive series of wind-tunnel experiments and numerical simulations will be performed to generate unprecedented data on flow over rough-walls subject to favourable and adverse pressure gradients (FPG and APG). The data will underpin identification and validation of potential universalities (and differences) in mechanisms of momentum/energy transfer compared to zero-pressure-gradient (ZPG) flows. The data will then be used to develop and validate both integral models and new Large-Eddy Simulation (LES) models that can be used to predict the performance of flow over arbitrary rough surfaces under the influence of varied pressure gradients. The data will be made available in the public domain through our roughness database (www.roughnessdatabase.org). The overall aim is to establish the interrelationship between roughness and pressure gradients over a broad range of parameters (for pressure gradient and roughness properties), understand the limitations of current models and develop new modelling methods that can be used for predictions in a wide range of applications.

A majority of engineering and environmental flows occur over surfaces that exhibit spatial variations in roughness and/or topography. When a turbulent wall-flow evolves over such surfaces, it may exhibit unusual physical properties, depending on the relationship between the dominant length-scales of the surface and that of the flow. Specifically, when the dominant length-scale(s) of the surface in the cross-stream direction become(s) comparable to the dominant length-scale of the flow (such as boundary layer thickness or water-depth), then the flow also exhibits large-scale spatial heterogeneity that is locked-on to the surface heterogeneity. This flow heterogeneity is expressed in the form of localised secondary currents (SCs) that often extend across the entire depth of the flow and manifest themselves as large 'time-averaged' streamwise vortices accompanied by low- and high-speed regions. This surface-induced flow heterogeneity invalidates some of the fundamental tenets of turbulent wall-flows that were developed for flows over homogeneous surfaces. Therefore, current predictive tools that rely on these tenets can neither accurately predict nor offer insights into the complex physics of flows that contain surface-induced SCs. The significant effects of surface-induced SCs have recently been recognised in at least two disparate areas: 1) Performance of engineering systems such as in-service turbine blades, bio-fouled ship hulls and flow control; and 2) Understanding of the river flow dynamics with applications in flood management, eco-hydraulics and sediment transport. Over recent years, Southampton, Aberdeen, Glasgow and UCL have invested considerable efforts in advancing both these areas. Given the burgeoning interest in this topic, it would be timely to harness the synergies between these four leading groups to develop comprehensive understanding of turbulent flows in the presence of surface-induced SCs and establish a novel transformative framework to predict such flows. This project will leverage the expertise, domain knowledge and infrastructure of four leading groups in the above-mentioned areas to bring about a paradigm shift in our approach to flows over heterogeneous surfaces that generate secondary currents. A comprehensive series of physical experiments (at Southampton & Aberdeen) and complementary numerical simulations (at Glasgow & UCL) will be performed to generate unprecedented data on surface-induced SCs. We will compare and contrast the behaviour of SCs across all four canonical wall-flows (boundary layers, open-channels, pipes and closed-channels) for the first time. The obtained data will underpin identification and validation of potential universalities (and differences) in drag mechanisms and momentum/energy transfer in these flows in the presence of surface-induced SCs. Synthesising the insights obtained from the data, a new framework leading to physics-informed semi-empirical and and theoretically-based numerical models will be developed to predict and optimise the influence of surface-induced SCs on turbulent wall-flows relevant to engineering/environmental applications.

This grant will deliver a step change in the understanding and predictability of next generation cooling systems to enable the UK to establish a global lead in jet engine and hypersonic vehicle cooling technology. We aim to make transpiration cooling, recognised as the ultimate convective cooling system, a reality in UK produced jet engines and European hypersonic vehicles. Coolant has the potential to enable higher cycle temperatures (improving efficiency following the 2nd law of thermodynamics) but invariably introduces turbine stage losses (reducing efficiency). Cooling system improvement must enable higher Turbine Entry Temperature (TET) while using the minimum amount of coolant flow to achieve the required component life. For high speed flight, heat transfer is dominated by aerodynamic heating with gas temperatures on re-entry exceeding those at the surface of the sun. Any reduction in heat transfer to the Thermal Protection System will ultimately lead to lower mass, allowing for decreased launch costs Furthermore, the lower temperatures could serve as an enabler for higher performance technologies which are currently temperature limited. The highest temperatures achievable for both jet engines and hypersonic flight are limited by the materials and cooling technology used. The cooling benefits of transpiration flows are well established, but the application of this technology to aerospace in the UK has been prevented by the lack of suitable porous materials and the challenge of accurately modelling both the aerothermal and mechanical stress fields. Our approach will enale the coupling between the flow, thermal and stress fields to be researched simultaneously in an interdisciplinary approach which we believe is essential to arrive at the best transpiration systems. This Progreamme Grant will enable world leaders in their respective fields to work together to solve the combination of cross-disciplinary problems that arise from the application of transpiration cooling, leading to rapid innovations in this technology. The application is timely since the proposed research would enable the UK aerospace industry to capitalise on recent developments in materials, manufacturing capability, experimental facilities/measurement techniques and computational methods to develop the science for the application of transpiration cooling. The High Temperature Research Centre at Birmingham University will provide the means to cast super alloy turbine aerofoils with porosity. The proposed grant would allow innovation in the cast systems arising from combining casting expertise with aerothermal and stress modelling in recent EPSRC funded research programmes. It also builds upon material development of ultra-high temperature ceramics and carbon composites undertaken in EPSRC funded research, by use of controlled porosity and multilayer composites. It will also provide the first opportunity to undertake direct coupling of the flow with the materials (porous and non-porous) at true flight conditions and material temperatures. Recent investment in the UK's wind tunnels under the NWTF programme (EPSRC/ATI funded) at both Oxford University and at Imperial College will allow for direct replication of temperatures and heat fluxes seen in flight and interrogated using advanced laser techniques. Recent development of Fourier superposition in CFD grids for modelling film cooling can now be extended to provide a breakthrough method to predict cooling flow and metal effectiveness for high porosity/transpiration cooling systems. The European Space Agency has recently identified the pressing requirement for alternatives to one-shot ablative Thermal Protection Systems for hypersonic flight. Investment in this area is significant and transpiration cooling has been identified as a promising cooling technology. Rolls-Royce has embarked upon accelerated investment in new technologies for future jet engines including the ADVANCE

The Centre for Doctoral Training in "Molecular Modelling and Materials Science" (M3S CDT) at University College London (UCL) will deliver to its students a comprehensive and integrated training programme in computational and experimental materials science to produce skilled researchers with experience and appreciation of industrially important applications. As structural and physico-chemical processes at the molecular level largely determine the macroscopic properties of any material, quantitative research into this nano-scale behaviour is crucially important to the design and engineering of complex functional materials. The M3S CDT offers a highly multi-disciplinary 4-year doctoral programme, which works in partnership with a large base of industrial and external sponsors on a variety of projects. The four main research themes within the Centre are 1) Energy Materials; 2) Catalysis; 3) Healthcare Materials; and 4) 'Smart' Nano-Materials, which will be underpinned by an extensive training and research programme in (i) Software Development together with the Hartree Centre, Daresbury, and (ii) Materials Characterisation techniques, employing Central Facilities in partnership with ISIS and Diamond. Students at the M3S CDT follow a tailor-made taught programme of specialist technical courses, professionally accredited project management courses and generic skills training, which ensures that whatever their first degree, on completion all students will have obtained thorough technical schooling, training in innovation and entrepreneurship and managerial and transferable skills, as well as a challenging doctoral research degree. Spending >50% of their time on site with external sponsors, the students gain first-hand experience of the demanding research environment of a competitive industry or (inter)national lab. The global and national importance of an integrated computational and experimental approach to the Materials Sciences, as promoted by our Centre, has been highlighted in a number of policy documents, including the US Materials Genome Initiative and European Science Foundation's Materials Science and Engineering Expert Committee position paper on Computational Techniques, Methods and Materials Design. Materials Science research in the UK plays a key role within all of the 8 Future Technologies, identified by Science Minister David Willetts to help the UK acquire long-term sustainable economic growth. Materials research in UCL is particularly well developed, with a thriving Centre for Materials Research, a Materials Chemistry Centre and a new Centre for Materials Discovery (2013) with a remit to build close research links with the Catalysis Technology Hub at the Harwell Research Complex and the prestigious Francis Crick Institute for biomedical research (opening in 2015). The M3S will work closely with these centres and its academic and industrial supervisors are already heavily involved with and/or located at the Harwell Research Complex, whereas a number of recent joint appointments with the Francis Crick Institute will boost the M3S's already strong link with biomedicine. Moreover, UCL has perhaps the largest concentration of computational materials scientists in the UK, if not the world, who interact through the London-wide Thomas Young Centre for the Theory and Simulation of Materials. As such, UCL has a large team of well over 100 research-active academic staff available to supervise research projects, ensuring that all external partners can team up with an academic in a relevant research field to form a supervisory team to work with the Centre students. The success of the existing M3S CDT and the obvious potential to widen its research remit and industrial partnerships into topical new materials science areas, which lie at the heart of EPSRC's strategic funding priorities and address national skills gaps, has led to this proposal for the funding of 5 annual student cohorts in the new phase of the Centre.