Investigation of alternative drag-reduction strategies in turbulent boundary layers by using wall forcing
Lead Research Organisation:
Imperial College London
Department Name: Aeronautics
Abstract
The aim of this research is to investigate, in an interactive programme involving several mutually supportive computational approaches and paradigms, the feasibility of achieving sustained and economically worthwhile frictional-drag reduction at flight Reynolds numbers using cross-flow wall forcing. While the emphasis of the programme is on the fundamental turbulence physics and the prediction of its interaction with wall drag, in general, the programme is closely associated with an important civil aviation goal, namely the reduction in emissions per passenger km by 50% by 2020. The programme will combine studies involving direct numerical simulations and highly-resolved large eddy simulations with two approaches based on linearised streak modelling, one developed by Chernyshenko (Imperial College) and the other by Lockerby (Warwick). The general strategy is to use the full-resolution schemes to gain insight into the near-wall turbulence mechanisms associated with frictional drag, to generate calibration-related input into the linearised streak modelling and to investigate the validity of this modelling for a range of actuation parameters examined with the full-resolution approaches. The proposed research is fundamental in nature and complements well EPSRC's Active Aircraft programme, which is practically-oriented. The ultimate objective is to derive a prediction procedure, based on linearised streak modelling that allows the effect of different configurations of cross-flow wall forcing on drag at flight Reynolds numbers to be quantified. The programme is financially supported by EADS.
Publications
Vodop'yanov I
(2013)
Turbulent drag reduction by spanwise oscillations of a ribbed surface
in Fluid Dynamics
Touber E
(2012)
Near-wall streak modification by spanwise oscillatory wall motion and drag-reduction mechanisms
in Journal of Fluid Mechanics
Olivier Blesbois (Author)
(2011)
Generalised optimal perturbation approach applied to drag reduction by wall oscillations in turbulent flows
Michael Leschziner (Author)
(2010)
On the physics of streamwise friction-drag reduction by spanwise oscillatory wall motion ? insight derived from turbulence simulations
in Keynote paper, XIX Polish National Fluid Dynamics Conference, Poznan, Poland.
Michael Leschziner
(2012)
The streamwise drag-reduction response of a boundary layer subjected to a sudden imposition of transverse oscillatory wall motion
in 9th Int. Symp. on Engineering Turbulence Modelling and Measurements
Mathis R
(2013)
Estimating wall-shear-stress fluctuations given an outer region input
in Journal of Fluid Mechanics
Lionel Agostini
(2013)
Spanwise oscillatory wall motion in channel flow: drag-reduction mechanisms inferred from DNS-predicted phase-wise property variations at Re=1000
in 8th Symp. on Turbulent Shear Flow Phenomena
Lardeau S
(2013)
The streamwise drag-reduction response of a boundary layer subjected to a sudden imposition of transverse oscillatory wall motion
in Physics of Fluids
Ghebali S
(2017)
Can large-scale oblique undulations on a solid wall reduce the turbulent drag?
in Physics of Fluids
Emile Touber
(2011)
Near-wall streak modifications by spanwise oscillatory wall motions
in 7th Int. Symp. on Turbulence and Shear Flow Phenomena
Duque-Daza C
(2012)
Modelling turbulent skin-friction control using linearized Navier-Stokes equations
in Journal of Fluid Mechanics
Duque C
(2011)
Modelling turbulent skin-friction control using linearised Navier-Stokes equations
in Journal of Physics: Conference Series
Chernyshenko Sergei
(2013)
Drag reduction by a solid wall emulating spanwise oscillations. Part 1
in arXiv e-prints
Chernyshenko S
(2019)
A large-scale filter for applications of QSQH theory of scale interactions in near-wall turbulence
in Fluid Dynamics Research
Blesbois O
(2013)
Pattern prediction by linear analysis of turbulent flow with drag reduction by wall oscillation
in Journal of Fluid Mechanics
Agostini L
(2015)
The turbulence vorticity as a window to the physics of friction-drag reduction by oscillatory wall motion
in International Journal of Heat and Fluid Flow
Agostini L
(2014)
Spanwise oscillatory wall motion in channel flow: drag-reduction mechanisms inferred from DNS-predicted phase-wise property variations at
in Journal of Fluid Mechanics
Agostini L
(2014)
On the influence of outer large-scale structures on near-wall turbulence in channel flow
in Physics of Fluids
Agostini L
(2016)
Skewness-induced asymmetric modulation of small-scale turbulence by large-scale structures
in Physics of Fluids
Agostini L
(2016)
Predicting the response of small-scale near-wall turbulence to large-scale outer motions
in Physics of Fluids
Agostini L
(2016)
On the validity of the quasi-steady-turbulence hypothesis in representing the effects of large scales on small scales in boundary layers
in Physics of Fluids
| Description | The research focused on computational and theoretical approaches to gaining insight into, and predicting, the physical processes associated with turbulent-friction-drag reduction by oscillatory wall motion. The objectives set out in the original application were fully achieved. A theoretical framework was developed, based on linear theory, to describe the near-wall-streak formation and its alteration by spanwise forcing. Alongside this theory, and in support of the same, extensive direct nume |
| Exploitation Route | The major interest of the Aeronautics sector in this research was identified and explained in the previous section. In addition, the research is very pertinent to ship hydrodynamics, high-speed trains and (to a more limited extent) to high-speed road transport. Especially In the first two areas, surface drag contributes significally to fuel consumption,. Both can, therefore, derive suignificant benefits from the results of this research. The project focused, primarily, on generic and fundamen |
| Sectors | Aerospace/ Defence and Marine |
| Description | The statement provided herein conveys the perception of the PI of the impact achieved by the project. From an academic perspective, the research has made a substantial contribution to understanding the interactions between turbulence and drag reduction. This knowledge will impact on approaches taken by future researchers in respect of active flow contyrol of near-wall flows. One particularly important interaction that has been identified relates to the role of strong turbulent structures in the outer flow on the near-wall streak stability, which is of major importance to the drag level. The identification of this role will steer future research towards controlling the outer structures, not simply the small-scale near-wall streaks, in an effort to reduce the drag. Substantial friction-drag reduction is the "holy grail" of civil aviation, and this is reflected by the significant financial support offered by EADS and Airbus UK, as well as its direct technical involvement. Neither has firm ideas about the engineering realisation of the knowledge derived from the project, simply because the major engineering challenges associated with forcing by wall motion need to be addressed. The time horizon of this challenge is thus at least 20 years. However, the UK's Aeronautics industry is extremely interested in pursuing all concepts leading to drag reduction and fuel savings, so as to remain competitive (especially against Boeing). It is especially interested in the promise of wall actuation at high (flight-condition) Reynolds numbers. The project partners therefore pushed their methods to the limit in terms of the proximity of the modelled conditions to reality, and this led to some important conclusions of major practical interest. In recognition of the relevance of exploitation issues, progress made by the academic project partners was presented at 5 workshops involving industry (Airbus, BAE Systems, EADS, various members of EU FP7). In addition, during the project, 6 1-day review meetings were held with industrial partners present. Finally, a closing 1-day open workshop was held, attended by several industrial representatives from the UK and abroad, with EADS making a presentation of its own conclusions derived from the project in relation to its future industrial strategy. . Beneficiaries: The academic flow-control and turbulent-flow communities; industrial researchers in the eronautical sector Contribution Method: First and foremost, the research has set markers in respect of the long-term potential of exploiting surface movement to achieve drag reduction in transport. Beyong this practice-related impact, the research has yielded knowledge and insight into how drag can be maniputated by creative near-wall straining. |
| Sector | Aerospace/ Defence and Marine |
| Impact Types | Cultural |