Turbulent Flow Simulations at the Exascale: Application to Wind Energy and Green Aviation

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Our daily life is surrounded - and even is sustained - by the flow of fluids. Blood moves through thevessels in our bodies, and air flows into our lungs. Fluid flows disperse particulate air pollution in the turbulent urban as well as indoor environments. Fluid flows play a crucial role for our transportation and our industries. Our vehicles move through air and water powered by other fluids that mix in the combustion chambers of engines. Many of the environmental and energy-related issues we face today cannot possibly be tackled without a better understanding of the dynamics of fluids.From a practical point of view, fluid flows relevant to scientists and engineers are turbulent ones; turbulence is the rule, not the exception. To date, a complete theory of fluid flow phenomena is still missing because of the complexity of the full equations describing the motion of a fluid.Their understanding and control is however crucial to improve technologies especially with minimal ecological impact as well as to anticipate events, in many areas ranging from engineering applications(e.g., industrial process, propulsion and power generation, car and aircraft design) to environmental sciences and technologies (e.g., air quality, weather forecasting, climate predictions, flood disasters monitoring).Significant progress has been made recently using petascale computing, and computational fluid dynamics is now a critical complement to experiments and theories. Turbulent flow simulations at the exascale will require significant reformulation of existing flow solvers, implementation of new physics, and development of a more nuanced problem formulation. It has however the potential to produce significant advances in our quest towards a greener future, relying in large parts on a better understanding of the overarching subject of turbulence.To better understand the opportunities and the challenges that will come with exascale computing for turbulent flows, we propose to create a Design and Development Working Group (DDWG) dedicated to turbulent flow simulations at the exascale, a high priority area of research for the UK. The focus will be on wind energy and green aviation applications as exascale computing will be a game changer in these areas and will contribute to make the UK a greener nation. This DDWG is building upon the experience and expertise of the UK Turbulence Consortium (UKTC) members and the recently funded Collaborative Computational Project (CCP) Turbulence. Two state-of-the-art open source flow solvers,OpenSBLI and Incompact3d, are currently being designed in the UK for pre-exascale and exascale systems using a high-level abstraction framework called OPS, an API with associated libraries and pre-processors to generate parallel executables for applications on multi-block structured meshes. The final output of this DDWG will be the delivery of a report with a strategic research agenda that will clearly articulate the research challenges to be overcome, opportunities, key risks and mitigation for turbulence simulations at the exascale. It will set out a detailed approach to enable development of CFD exascale-ready software through appropriate application-oriented, high-level programming abstractions, with proof-of-concept studies to demonstrate the capabilities of OpenSBLI and Incompact3d for exascale computing.