Deterministic Turbulence

Lead Research Organisation: Cranfield University
Department Name: Sch of Aerospace, Transport & Manufact

Abstract

"Turbulence is the most important unsolved problem of classical physics" (Richard Feynman) due to its high non-linearity and chaotic behaviour. Therefore, it has been widely accepted that turbulence is not repeatable even with identical initial and boundary conditions (i.e. the butterfly effects). Recently, however, a Russian research group led by Prof Kachanov (Visiting Researcher of this proposal) observed a certain set of repeatable flows in a very late stage of laminar-to-turbulent transition, which can be considered as turbulence as far as its statistics are concerned. These are called deterministic turbulence. Unlike "ordinary" turbulence, the deterministic turbulence allows us to predict the exact time and location of turbulence events that take place in the flow. One can also go back the flow history to see the cause of turbulence events. This provides an exciting opportunity for turbulence research that has not been possible before. Here we propose to utilise the deterministic turbulence to better understand the turbulent boundary-layer structures with a view to develop an innovative strategy for turbulence control and optimise existing flow control techniques.
 
Description Numerical Simulations are able to reproduce previous experimental observations for some forced transitional boundary layer flows, and have provided support for the existence of Deterministic Turbulence under specified conditions as part of evidence emerging from the project as a whole; with Airbus/BAE recognising the importance of these findings. In particular Simulations for initial laminar flow wave instabilities, with appropriately scaled white-noise forcing, have been found to agree closely with the experimental data obtained by collaborating partners in this joint institutional grant, and there is agreement, also with Russian research advisors who conducted original research, that a more coherent transitional turbulence state has been generated. This has allowed more detailed examination of the richer numerical database to be conducted, to complement the necessarily limited experimentally obtained data, and an attempt to be made, in both the experiments and simulations, to establish more beneficial control of the more ordered flow structure. Latest numerical simulations have now been conducted for a forced self-similar laminar boundary layer using a point source Tollmien-Schlichting (TS) wave with some broadband noise superposed to produce a transitional boundary layer exhibiting typical level of uncertainty. Reproducible turbulent structures have again been detected experimentally in the late stages of transitional and early stages of turbulent boundary layer ?ow. These deterministic structures allow control strategies acting on the turbulent spots to be developed and tested. As a result in final work, different control jet con?gurations have been used to successfully target selectively the near wall high momentum region of the turbulent spots, with beneficial results. At the same time some implications for improved sub-grid scale modelling have emerged from simulations of the more ordered transitional deterministic turbulence regimes.
Exploitation Route The now verified existence of Deterministic Turbulence should allow further improvements to both flow control and prediction methodologies.
Sectors Aerospace, Defence and Marine,Energy,Transport

URL http://www.ukturbulence.co.uk
 
Description ARCHER Resource allocation of 21.8M AU
Amount £6,900,000 (GBP)
Funding ID EP/R029326 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2019 
End 07/2019
 
Description UKTC HEC ARCHER Resource Allocation of 18.7M AU
Amount £11,000,000 (GBP)
Funding ID EP/L000261 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 11/2017 
End 06/2018
 
Title Computational Simulations 
Description Time-series computational flow simulations and restart data - for Navier-Stokes Simulations and/or Lattice Boltzmann Method schemes. 
Type Of Material Database/Collection of data 
Year Produced 2012 
Provided To Others? Yes  
Impact Enabling subsequent analyses and comparative simulations with other computational and mathematical modelling methods to improve academic understanding and prediction methods for industry, as well as verifying, supporting, and extending complementary experimental data taking. 
 
Description Airbus Operations Ltd 
Organisation Airbus Group
Department Airbus Operations
Country United Kingdom 
Sector Private 
PI Contribution Joint EPSRC Project collaboration with our group responsible for more fundamental computational simulation studies against experiment and mathematical formulae.
Collaborator Contribution Technical interactions and advice.
Impact As for Joint Project partners University of Cambridge
Start Year 2010
 
Description City University Flow Control Group 
Organisation City, University of London
Country United Kingdom 
Sector Academic/University 
PI Contribution Numerical simulations to complement experimental data taking.
Collaborator Contribution Experimental set-up and data taking to provide initial conditions and validation for simulations.
Impact None as yet
Start Year 2016
 
Description Nottingham University Flow Control Group 
Organisation University of Nottingham
Country United Kingdom 
Sector Academic/University 
PI Contribution Numerical Simulations to complement experimental data taking.
Collaborator Contribution Experimental set-up and data taking to provide initial conditions and validate simulations.
Impact None as yet
Start Year 2016
 
Description Novosibirsk Flow Control Group 
Organisation University of Novosibirsk
Country Russian Federation 
Sector Academic/University 
PI Contribution Numerical simulations in support of experimental data taking at City and Nottingham University.
Collaborator Contribution Advising on present project direction, focus and both experimental and numerical set-ups as well as their own previous published and un-published methodologies and findings.
Impact None as yet
Start Year 2016
 
Description University of Cambridge (Engineering) 
Organisation University of Cambridge
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaborative developments and extensions to the SENGA2 code for Direct Numerical Simulations of wall-bounded shear flows.
Collaborator Contribution Provision of a new research version of the SENGA2 code with wall boundary provisions and associated mesh stretching capability.
Impact None as yet.
Start Year 2016
 
Title SENGA2 version for wall -bounded flows 
Description An extended version of the SENGA2 DNS Code with stretched meshing option for application to (non-combusting) wall-bounded shear flows. 
Type Of Technology Software 
Year Produced 2017 
Impact None as yet