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

Lead Research Organisation: Imperial College London
Department Name: Dept of Aeronautics

Abstract

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.

Planned Impact

Turbulence is relevant to the transportation, energy supply/generation, biomedical and process sectors in the UK and the world. In addition to creating new software and knowledge, the proposed agenda and the resulting scientific outputs will deliver benefits to the economy and allow the UK to realise its societal goals, especially the one of being a greener nation.

Despite being the largest contributors to harmful emissions, the transportation, energy generation/supply and process sectors are experiencing unprecedented growth around the world. For example, it is estimated that more than 29,000 new large civil airliners, 24,000 business jets, 5,800 regional aircraft and 40,000 helicopters will be required worldwide in 2032 to deal with the constant increase of worldwide air traffic. It is predicated that by 2025 there will be more than 16 billion passengers per year worldwide. The UK is directly concerned by this challenge as it is the second biggest national aerospace industry in the world, with a 17% global market share for a turnover of more than £20 billion every year, sustaining more than 200,000 jobs. Aviation will need to find ways to meet this impressive growing demand whilst reducing its environmental impact - specifically the noise levels and carbon emissions. This can only be achieve with a state-of-the-art ecosystem of exascale-ready software for a better understanding of the overarching subject of turbulence. Many of the UK Turbulence Consortium members and CCP Turbulence members, in collaboration with AIRBUS and the US Air Force, are currently working on drag reduction techniques for airplanes, high-speed trains, automotive vehicles and over the hulls of ships and submarines. Even a 1% reduction in drag can save at least 25,000 gallons of fuel per year per aircraft. Worldwide, this reduction could translate to fuel savings of more than $1 billion per year. The resulting reduction in emissions into the air is equally as impressive.

Since the mid-1990s, Computational Fluid Dynamics (CFD) has been integrated into industrial design and engineering processes, playing a decisive role in improving the quality and efficiency of complex products and significantly reducing the time to market. Petascale computing has enabled simulations at a higher level of precision and complexity, significantly impacting new areas of research. CFD is now recognised as a driver of economic growth and societal well-being and is vital for maintaining international competitiveness. The UK has a long history in Europe of developing cutting-edge applications dedicated to CFD. Because of the rapid evolution of the enabling technologies and the expanding range of applications demand, the UK needs to support and encourage the development of exascale-ready flow solvers, which can produce new knowledge, help to design innovative products and reduce cost and time of their implementation in real life applications. A striking example is the recent purchase by Siemens of the CFD software company CD-Adapco for $970M which clearly shows that turbulence simulations that can improve engineering design for a great range of applications are crucially needed by industries. Our industrial partners, heavily involved with several members of the UK Turbulence Consortium members, believe that exascale computing is crucial to gain insights into turbulence physics and would enabled them to better understand limitations of petascale computing and how to devise improvement strategies to take a competitive lead.

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