Understanding and exploiting non-equilibrium effects on turbulent boundary layers: Towards realisable drag reduction strategies
Lead Research Organisation:
Imperial College London
Department Name: Aeronautics
Abstract
Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.
Publications
Bird J
(2018)
Experimental Control of Turbulent Boundary Layers with In-plane Travelling Waves
in Flow, Turbulence and Combustion
Bird J
(2018)
Compliant kagome lattice structures for generating in-plane waveforms
in International Journal of Solids and Structures
Diwan S
(2021)
Intermediate scaling and logarithmic invariance in turbulent pipe flow
in Journal of Fluid Mechanics
Fumarola I
(2024)
Simultaneous Measurements of Surface Spanwise Waves and Velocity in a Turbulent Boundary Layer
in Flow, Turbulence and Combustion
Soltani Z
(2022)
Refined Unified Formulation for Efficient Folding and Unfolding Analyses of Slender Thin-Walled Structures
in AIAA Journal
Soltani Z
(2020)
The determination and enhancement of compliant modes for high-amplitude actuation in lattices
in International Journal of Solids and Structures
Vemuri S
(2018)
Real-time feedback control of three-dimensional Tollmien-Schlichting waves using a dual-slot actuator geometry
in Physical Review Fluids
Zhu T
(2021)
Simulation of the turbulent axisymmetric bluff body wake with pulsed jet forcing
in Physical Review Fluids
| Description | Design of kagome lattice for drag reduction is scaleable for larger applications. We have developed a larger operational surface (3m x 1m) for use in a larger wind tunnel in which a 'big and slow' boundary layer can be developed where it has a sufficient development length so that it conforms to the new surface condition of a travelling surface wave. The boundary layer size enables good resolution and the kagome lattice can be driven at quite low frequencies with quite large amplitudes. |
| Exploitation Route | While experiment is unique, results are likely to be taken forward. The PI has been awarded a Royal Society Industry Fellowship (with QinetiQ as partner) "Drag reduction for new airframe design". The aerospace sector is now particularly receptive to innovation and the challenges in reducing emissions by adopting alternative energy sources such as batteries or liquid hydrogen for propulsion. In the development of low-carbon, aerodynamically efficient transport, drag reduction is essential in the airframe design of new aircraft so that the range for a given payload is as large as possible. We will exploit novel concepts of dynamic surface and new materials to achieve significant drag and power reductions. For practicable drag reductions at flight conditions, an understanding of the fluid mechanics of near-wall fluid motion is required in order to exploit the anticipated changes in behaviour at high Reynolds number. While there is still much to be understood, exploitation of these changes is likely to require the development of new techniques and surfaces that are either passive (e.g. metasurfaces) or can operate at the high frequencies and small amplitudes of flight conditions. For the latter, the use of in-surface acoustic "Lamb" waves may be beneficial. The project is therefore also about the synthesis of ideas and expertise from a range of disciplines. Therefore collaboration is essential where laboratory proven concepts can be developed to operate in the 5m Wind Tunnel at QinetiQ that can replicate flight conditions. The purpose of the fellowship is to stimulate and provide resources for research projects that lead to the establishment of technology platforms focused on the grand challenges of green economic growth and the future of mobility. |
| Sectors | Aerospace Defence and Marine |
| Description | Drag reduction attained is, so far, 20%. Key challenge is how surface waves might be developed and implemented for practical configurations. These involve much higher frequencies and smaller amplitudes. Simulations and experiments have demonstrated that skin friction drag reduction greater than 40% can be achieved by a moving wall with different types of motion, such as oscillating walls or spanwise surface waves travelling in the streamwise direction (Bird et al. 2018, Marusic et al. 2021). Nevertheless, many open questions remain on how surface waves interact with the turbulent boundary layer. To this end, we have ongoing systematic experiments to investigate the effectiveness and the mechanism of the active control at high Reynolds number. The surface is able to generate spanwise standing waves at different amplitudes and frequencies allowing a wide range of wave parameters. Work also focuses on the development of simultaneous measurements of the flow field and of the surface deformation by combining Particle Image Velocimetry (PIV) with Digital Image Correlation (DIC). The methodology proposed here provides a valid tool to experimentally investigate the fluid structure interaction between spanwise waves and turbulent boundary layer. This approach of combining the two experimental techniques provides a powerful tool for unveiling some of the unknowns concerning the interaction between a surface wave and the turbulent boundary layer. In this work, results of time-resolved PIV synchronised with DIC for a range of actuated parameters have been obtained. Current implementation includes the generation of in-plane, standing and travelling surface waves of variable amplitude and frequency via an array of mechanically and pneumatically driven rods and their integration with a kagome lattice and a silicone skin to produce spatially well-defined sinusoidal waves. |
| First Year Of Impact | 2014 |
| Sector | Aerospace, Defence and Marine |
| Description | Airbus support for student |
| Organisation | Airbus Group |
| Department | EADS Innovation Works |
| Country | United Kingdom |
| Sector | Private |
| PI Contribution | Overhead contributions in respect of staff time and estates. |
| Collaborator Contribution | Direct support for PhD student over 4 years + consumables |
| Impact | Papers, aerodynamics, and adaptive / morphing structures |
| Start Year | 2012 |