A dynamical systems analysis of high-Reynolds-number wall turbulence
Lead Research Organisation:
Imperial College London
Department Name: Aeronautics
Abstract
Turbulence in fluid flows over a solid surface (i.e. wall turbulence) is ubiquitous and central to the design of many aeronautical- and mechanical-engineering devices, such as aircraft wings, ship hulls, trains, cars, turbine blades, pipelines, and heat exchangers. The momentum transfer in wall turbulence is dominated by highly-organised energy-containing fluid motions, often referred to as coherent structures. There is a growing body of recent evidence that wall turbulence at high Reynolds numbers is organised into a hierarchy of self-similar, self-sustaining coherent structures, the size of which is proportional to their distance from the wall. Recently, the group of the applicant has discovered a set of exact solutions of the Navier-Stokes equations, which are directly linked with these self-similar coherent structures. In dynamical systems theory, such exact solutions form a skeleton of chaotic dynamics of turbulence in `state space'. Motivated by this recent discovery, this proposal aims to formulate and examine a dynamical-systems-theory-based description of wall turbulence at high Reynolds numbers. To this end, the present proposal sets out two work packages based on the state-of-the-art understanding of wall turbulence: 1) Computation of self-similar time-periodic solutions (periodic orbits) for the dynamics of individual coherent structures; 2) Dynamical systems analysis of minimal multi-scale (two-scale) wall turbulence. The outcome of this proposal will provide fundamental physical insight into the individual and collective dynamics of coherent structures in high-Reynolds-number wall turbulence. In particular, it will form a key building-block knowledge in a low-dimensional description of high-Reynolds-number wall turbulence. Ultimately, this will play a pivotal role in illuminating the precise `dynamical' mechanisms of turbulent skin-friction generation, heat transfer, and noise generation, the central processes underpinning many industrial designs.
Planned Impact
A growing body of recent evidence has been supporting that the dynamics of turbulent flows at high Reynolds numbers may well be approached with suitable extensions of the notions of dynamical systems theory previously used to study transition and turbulence at low Reynolds number. Given the nature of the proposed research, which exercises these notions for high-Reynolds number turbulence, its main output will be knowledge in the form of scientific papers to be published in leading fluid mechanics journals. Therefore, the primary and immediate beneficiaries from the proposed research will be academics working on fluid dynamics (applied mathematicians, statistical physicists and engineers).
The fundamental research of wall-bounded shear flows, such as channel flow, pipe flow and boundary layers, underpins the technologies concerning development of aircrafts, ships, trains, turbo-machineries and heat exchangers. It is also crucial to understand atmospheric surface layer, a popular location for wind energy harvesting. With this nature, the proposed research will deliver an improved description on the mechanisms of turbulent skin-friction generation, heat transfer and noise generation. As such, it would be highly valuable for the early-stage design processes of next-generation transportation products and wind-energy farms, ultimately offering a long-term benefit for manufacturing and energy industries.
The fundamental research of wall-bounded shear flows, such as channel flow, pipe flow and boundary layers, underpins the technologies concerning development of aircrafts, ships, trains, turbo-machineries and heat exchangers. It is also crucial to understand atmospheric surface layer, a popular location for wind energy harvesting. With this nature, the proposed research will deliver an improved description on the mechanisms of turbulent skin-friction generation, heat transfer and noise generation. As such, it would be highly valuable for the early-stage design processes of next-generation transportation products and wind-energy farms, ultimately offering a long-term benefit for manufacturing and energy industries.
People |
ORCID iD |
Yongyun Hwang (Principal Investigator) |
Publications
Bengana Y
(2022)
Exact coherent states in plane Couette flow under spanwise wall oscillation
in Journal of Fluid Mechanics
Chua Khoo Z
(2022)
A sparse optimal closure for a reduced-order model of wall-bounded turbulence
in Journal of Fluid Mechanics
Doohan P
(2021)
Minimal multi-scale dynamics of near-wall turbulence
in Journal of Fluid Mechanics
Doohan P
(2022)
The state space and travelling-wave solutions in two-scale wall-bounded turbulence
in Journal of Fluid Mechanics
Hernández C
(2022)
Generalised quasilinear approximations of turbulent channel flow. Part 1. Streamwise nonlinear energy transfer
in Journal of Fluid Mechanics
Hernández C
(2022)
Generalised quasilinear approximations of turbulent channel flow. Part 2. Spanwise triadic scale interactions
in Journal of Fluid Mechanics
Holford J
(2023)
Optimal white-noise stochastic forcing for linear models of turbulent channel flow
in Journal of Fluid Mechanics
Hwang Y
(2021)
The logarithmic variance of streamwise velocity and conundrum in wall turbulence
in Journal of Fluid Mechanics
Hwang Y
(2020)
The mean logarithm emerges with self-similar energy balance
in Journal of Fluid Mechanics
Jiao Y
(2022)
A driving mechanism of near-wall turbulence subject to adverse pressure gradient in a plane Couette flow
in Journal of Fluid Mechanics
Description | Potential and limitations in viewing turbulence using the theories for chaos are understood, while some new dynamical processes of tubulence related to drag generation are discovered. |
Exploitation Route | The knowledge gained by this research has been published leading Fluid Mechanics Journal, and this will be able to be exploited by practitioners or engineers. |
Sectors | Aerospace, Defence and Marine,Energy |
Description | Dynamical systems analysis of turbulent boundary layer under adverse pressure gradient |
Amount | £15,361,293 (GBP) |
Funding ID | 2368066 |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 01/2020 |
End | 06/2023 |
Description | Scale interaction in wall turbulence |
Organisation | University of Paris-Saclay |
Country | France |
Sector | Academic/University |
PI Contribution | We have just built contribution. We are currently writing a proposal together. |
Collaborator Contribution | We have just built contribution. We are currently writing a proposal together. |
Impact | Not yet. |
Start Year | 2019 |
Description | A seminar given in the Department of Mathematics, Imperial College London |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | About 60 academics, postdocs and postgraudate students attended for a seminar. The talk is recorded and is presented online. |
Year(s) Of Engagement Activity | 2022 |
URL | https://www.youtube.com/watch?v=4xE5acZNk20&t=3389s |
Description | A talk or presentation - Give a talk in Annual Division of Fluid Dynamics Meeting in American physical socieity: A sparse optimal closure for a reduced-order model of wall-bounded turbulence |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | About 2000 academics, UG and PG students and postdocs attended for an international conference represending their annual research outputs. |
Year(s) Of Engagement Activity | 2021 |
Description | A talk or presentation - Give a talk in Annual Division of Fluid Dynamics Meeting in American physical socieity: Wall-bounded turbulent flow and equilibrium states in plane Couette flow under spanwise wall oscillation |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | About 2000 academics, UG and PG students and postdocs attended for an international conference represending their annual research outputs. |
Year(s) Of Engagement Activity | 2022 |
Description | APS DFD meeting in Indianapolis |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Attended Annual Division of Fluid Dynamics Meeting in American Physical Society, and four people are attended from my group. Among them, Dr Yacine Bengana presented his on-going EPSRC-funded research and myself also gave an oral presentation. |
Year(s) Of Engagement Activity | 2022 |
URL | https://www.apsdfd2022.org/ |
Description | European Fluid Mechanics |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | Attended European Fluid mechanics conference held in Athens and presented the on-going research. From my group, four people attended. Among them, Dr Yacine Bengana gave a presentation on his EPSRC-funded research. |
Year(s) Of Engagement Activity | 2022 |
URL | https://www.efmc14.org/ |
Description | Give a talk in Annual Division of Fluid Dynamics Meeting in American physical socieity: Wall-bounded turbulent flow and equilibrium states in plane Couette flow under spanwise wall oscillation |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | About 2000 academics, UG and PG students and postdocs attended for an international conference represending their annual research outputs. |
Year(s) Of Engagement Activity | 2021 |
URL | https://www.apsdfd2021.org/ |
Description | Given a seminar in the series of Shear Flow Instability, Transition and Turbulence by Department of Mathematics, Monash University |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | 60 people (academic, graudate students, funding agencies) attended for an online seminar taken place during pandemic. |
Year(s) Of Engagement Activity | 2020 |
Description | Invited as a participant in the Isaac Newton Institute Programme on Mathematical aspects of turbulence: where do we stand? |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | About 100 internationally renowned acadmics and postdocs attended for communications of their research and development of collabirations -- currently developing a possible collaboration. |
Year(s) Of Engagement Activity | 2021 |
Description | Invited seminar in IST Austria |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Postgraduate students |
Results and Impact | The complex Physics group led by Prof. B Hof attended to listen the seminar. This has developed new collaboration with his grou. |
Year(s) Of Engagement Activity | 2023 |
Description | Invited seminar in University of Keele |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Postgraduate students |
Results and Impact | About 30 academics, postdocs and PhD students attended for my seminar given in Keele University. They showed increased interest in my research. |
Year(s) Of Engagement Activity | 2022 |
Description | UK fluids conference |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Professional Practitioners |
Results and Impact | About 200 acadmics, UG and PG students and postdocs attend for a national conference on fluid mechanics, which sparked questions and discussion afterward with colleagues. |
Year(s) Of Engagement Activity | 2021 |
URL | https://www.southampton.ac.uk/engineering/news/events/2021/09/10-uk-fluids-conference-2021.page |