Determining the Effects of Competing Instabilities in Complex Rotating Boundary Layers

Lead Research Organisation: Manchester Metropolitan University
Department Name: Sch of Computing, Maths and Digital Tech

Abstract

Fluid mechanics is of fundamental importance and underpins key developments in a range of disciplines, including aerospace, defence, energy and environmental research. For example, the efficient use of fuel has become an increasingly important factor in civil aviation, with the International Air Transport Association (IATA) committed to "reducing fuel consumption and CO2 emissions by at least 25% by 2020, compared with 2005 levels". Concurrently, aircraft engine noise has become a real and growing environmental issue, especially in the vicinity of airports around the world.

Given the global demand for increased air travel, energy efficient and quieter aeroengines are important targets for the aviation and aerospace industries. Aerodynamic improvements have the potential to contribute to the design of the next generation of energy-efficient aeroengines and tubomachinery. Specifically, an increased understanding of the underlying physics through active flow control can reduce aerodynamic drag and delay the transition to unstructured, turbulent flow, both of which are known to have negative implications for fuel consumption and noise emissions. The goal of delaying turbulent-transition can be achieved in a cost-effective way through detailed numerical simulations, as opposed to comparatively expensive experimental investigations. This project will help to achieve that goal by applying a novel computational approach that can model flow within the boundary layer over complex rotating geometries.

The boundary layer, a thin layer of fluid confining its viscosity close to a bounding surface, can influence the aerodynamics and drag characteristics of a fluid flow in a profound and significant way. Historically, the boundary layer flow over a rotating disk was used to model air flow over a swept-wing due to the similarity between their velocity profiles. Today, continuing developments in aeroengines, turbomachinery, spinning projectiles and, more recently, electrochemical applications, has created the need to understand boundary-layer flows over rotating bodies, such as disks, spheres and cones. Indeed, rotating 3D boundary-layer flows are now known to exhibit numerous flow characteristics, governed by highly complex and often competing mechanisms that cause flow instability and eventual breakdown to turbulent flow. For a family of rotating cones, experiments have observed a continuous change of flow characteristics as the governing flow parameters are altered. The applicant has shown that this change arises from an interaction between various forces governing flow within the boundary layer. However, the nature of this competing interaction remains largely unknown. With this in mind, this research project will develop a complex computational modelling code capable of providing robust and accurate quantitative predictions of the interaction between competing flow instability mechanisms in the turbulent-transition process. Such predictions can help to accelerate aerodynamics research, and inform or form part of innovative flow control strategies to reduce drag, thereby improving fuel consumption, as well as decreasing harmful noise and CO2 emissions.

Planned Impact

The long-term objective is to inform the advancement of innovative flow control strategies to reduce drag in a range of aerodynamic, industrial and environmental applications, through a complex modelling capability that provides accurate and robust numerical simulations of realistic models. Given the proposed benefits of hydrodynamic stability theory in generating precise, cost-effective predictions compared with experiments, along with revealing flow control and drag reduction strategies, the potential environmental and economic benefits (resulting from reduced noise, CO2 emissions and fuel consumption) are significant. The beneficiaries and impact pathways directly arising from this project, which are crucial to the long-term objective, are outlined below.

Academic beneficiaries: Impact activities are vital in the short term to achieve longer term economic and societal impact. Aerodynamics research scientists/engineers will benefit directly from the findings of the proposed research, which will inform the development of experimental methodologies and active flow control techniques and thereby accelerate the development of the next generation of noise- and fuel-efficient aeroengines. In addition to dissemination through aerospace journals/conferences, the impact of this research will be promoted through forging new collaborative links with experimental scientists/aerodynamics researchers/engineers in the UK, via the PI's links with the UKFN, and internationally. This will likely result in cross-disciplinary research partnerships that will serve to strengthen the UK's competitiveness and reputation as a world-leader in aerodynamics research. It is also possible that the spectral stability code output from this project will advance the state-of-the-art in computational tools and form part of active flow control strategies on rotating-body flow applications, for use by researchers and engineers.

Commercial beneficiaries: The findings of this project will be of interest to the commercial developers of aeroengine and turbomachinery components in aerospace, aviation and industrial applications. Companies manufacturing aeroengines and turbofan components (such as Airbus, Rolls-Royce and Dyson UK) will be interested in the outputs of this project (including the developed stability codes), which can offer insights into their research and development of improved airflow characteristics for rotating aerodynamics applications. The PI will work closely with the Research and Knowledge Exchange (RKE) department (an MMU organisation dedicated to supporting the transition of academic enterprises into the commercial and public sectors), as well as with the UKFN Special Interest Groups, to explore and initiate potential research commercialisation opportunities. A one-day workshop will also be organised towards the end of this project to which the relevant commercial and academic parties will be invited. Along with fostering external collaboration, this event will explore the potential commercial exploitation and industrial benefits of the project outputs.

Young researchers: Through his departmental role in the delivery of the MMath programme, the PI undertakes significant research-led teaching at Master's level, which is targeted at developing and training successful PhD students in fluid mechanics. The economic and societal impact of inspiring young people to become scientists/applied mathematicians is clearly a critical impact pathway. In this role, impact activities will include a PhD project on the PI's research into boundary-layer stability theory employing asymptotic methods, which is not only directly related to this project but also funded by his School. Such activities will be complemented by the ongoing online dissemination and feedback of the project's findings via the PI's research group's social networking sites, Twitter, Facebook, and YouTube, as well as the research group's homepage.
 
Description The project has focused on the nature of competing instabilities in the complex boundary-layer flows for broad and slender rotating cones within oncoming axial flow. The effects of the dominant parameters on the governing stability curves have been observed for the first time in both cases. Furthermore, a new computational platform has been developed, which employs a fully object-oriented approach to implementing the stability algorithm. Consequently, the flexibility and adaptability of the approach enables it to be extended and applied seamlessly to a wide range of related flow stability problems over and above the original project objectives.

This approach has ignited two new research pathways, which are currently being explored via testing the existing code. Firstly, with colleagues at University of Leicester, the scope to extend the platform to a nonlinear model is being tested. Secondly, the code is being extended to investigate the stability of swirling jet flow in a lined duct with a PhD project now in place to collaborate with Prof. Nigel Peake at DAMTP, Cambridge.
Exploitation Route Firstly, the project has influenced experimental research as part of the ASTRID project at the Linne FLOW Centre at KTH, Sweden (project partner) and more recently the Flight Performance and Propulsion Group, Delft, Netherlands. Secondly, the computational platform which has been built has the potential to by utilised by others to investigate more general flow stability problems in other complex and non-rotating geometries. The tool has significant potential for use in a range of areas, including aviation, energy-conversion and electro-chemical applications.
Sectors Aerospace, Defence and Marine,Energy

 
Description The evolving findings from this award have been presented at a UK Fluids Network (UKFN) Research Meeting during 2019 and subsequently has led to Hussain taking up leadership of the 'Boundary Layers and Complex Rotating Flows' Special Interest Group. This has engendered commercial interaction with potential industrial partners at Thales UK, Dyson UK and further afield with partners at TU Delft. There are current plans for collaboration, as well as future follow-up industrial proposals, enabling Hussain to lead a consortium of UK-wide and internationally renowned specialists within the field. Furthermore, the UKFN SIG forum has enabled Hussain to engage in outreach at grass-roots level, inspiring young researchers at undergraduate level to become interested in rotating boundary layer flows, which has attracted interest in related PhD projects.
First Year Of Impact 2019
Sector Aerospace, Defence and Marine
Impact Types Economic

 
Description EPSRC COVID-19 Allocation Funding
Amount £9,892 (GBP)
Organisation University of Leicester 
Sector Academic/University
Country United Kingdom
Start 03/2021 
End 09/2021
 
Description Research collaboration on Blasius flow and rotating disk to test CHESS code 
Organisation University of Leicester
Country United Kingdom 
Sector Academic/University 
PI Contribution Provided code in development for the rotating cone in order to test its accuracy and efficiency for a simpler Blasius and rotating disk flow
Collaborator Contribution Used base code for simple geometries to prototype its operation.
Impact R. Miller, PT. Griffiths, Z. Hussain, S. J. Garrett (2020). On the stability of a heated rotating-disk boundary layer in a temperature-dependent viscosity fluid. Physics of Fluids. 32(2), pp.024105-024105. R. Miller, S. J. Garrett, P. T. Griffiths, Z. Hussain (2018). Stability of the Blasius boundary layer over a heated plate in a temperature-dependent viscosity flow. Physical Review Fluids. 3(11)(113902), pp.1-36.
Start Year 2018
 
Description Research collaboration on rotating cone experiments in axial flow 
Organisation Delft University of Technology (TU Delft)
Country Netherlands 
Sector Academic/University 
PI Contribution Research seminars and exchange of data to steer experiments and compare findings on boundary layer flow measurements over rotating cone in axial flow.
Collaborator Contribution Development of collaborative research outputs, currently in prepartion
Impact In progress.
Start Year 2020
 
Description Research collaboration on rotating cone experiments in still fluid 
Organisation Royal Institute of Technology
Country Sweden 
Sector Academic/University 
PI Contribution Research seminars and exchange of data to steer experiments and compare findings on boundary layer flow measurements over rotating cone in still fluid.
Collaborator Contribution Development of collaborative research outputs currently in preparation
Impact In progress
Start Year 2018
 
Description Research collaboration on slender cone in axial flow 
Organisation Indian Institute of Technology Gandhinagar
Country India 
Sector Academic/University 
PI Contribution Sharing of new data and research findings in order to develop research outputs.
Collaborator Contribution Development of global stability code based loosely on CHESS code from this project and tested against related research problems.
Impact R. Bhoraniya, Z. Hussain, V. Narayanan (2021). Global stability analysis of the axisymmetric boundary layer on a slender circular cone with the streamwise adverse pressure gradient. European Journal of Mechanics - B/Fluids. 87, pp.113-127.
Start Year 2020
 
Title CHEbyshev Spectral Solver (CHESS) 
Description CHESS is the manifestation of the Spectral Stability Code proposed at the beginning of this research project. The code has evolved significantly from a linear programming code in Matlab to an object-oriented programming (OOP) tool within the C++ platform, which has enabled significant automation and the full use of inheritance, encapsulation and polymorphism within the code structure. This has enabled the programme to make use of automatic differentiation to improve efficiency and accuracy, as well as extended the applicability of the solver to more complex 3D problems. As a result, CHESS has formed the basis for a wider programme of research aimed at more general flow stability problems. This research pathway is now being realised via a funded PhD project, which will investigate the stability of swirling jet flow in a lined duct, in collaboration with colleagues at DAMTP, Cambridge. 
Type Of Technology New/Improved Technique/Technology 
Year Produced 2020 
Impact Fully funded PhD project award (£60k) 
 
Description Research Visit (China) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Seminar talk to research colleagues to develop collaboration and disseminate findings.
Year(s) Of Engagement Activity 2021
 
Description Research Visit (Japan) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Seminar talk to research colleagues to develop collaboration and disseminate findings.
Year(s) Of Engagement Activity 2020
 
Description Research Visit (Sydney) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Seminar talk to research colleagues to develop collaboration and disseminate findings.
Year(s) Of Engagement Activity 2019
 
Description Research Visit (Sydney) 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Seminar talk to research colleagues to update progress, develop collaboration and disseminate findings.
Year(s) Of Engagement Activity 2021