The project “Drag Reduction via Turbulent Boundary Layer Flow Control” (DRAGY) approaches the problem of turbulent drag reduction through the investigation of active/passive flow-control techniques to manipulate the drag produced by the flow structures in turbulent boundary layers. In addition, making use of new algorithms and exploiting efficiently large computing facilities, the project aims to improve the understanding of the underlying physics behind the control techniques and its interaction with the boundary layer to maximize their efficiency.

Turbulent Boundary Layer Control (TBLC) for skin-friction drag reduction is a relatively new technology made possible through the advances in computational-simulation capabilities, which have improved our understanding of the flow structures of turbulence. Advances in micro-electronic technology have enabled the fabrication of actuation systems capable of manipulating these structures. The combination of simulation, understanding and micro-actuation technologies offer new opportunities to significantly decrease drag, and by doing so, increase fuel efficiency of future aircraft. The literature review shows that the application of active control turbulent skin-friction drag reduction is considered of prime importance by industry, even though it is still at a very low Technology Readiness Level (TRL =1). Given the scale of the “Flightpath 2050” challenge, now is the appropriate time to investigate the potential of this technology and attempt to raise the TRL to 2 or possibly 3 in some particular branches of the subject. DRAGY is a Europe-China R&T collaborative effort specifically focused on active and passive control for turbulent skin-friction drag reduction.

The project will result in mutual benefits for industry and scientific European as well as Chinese communities, in a topic of growing concern, namely drag-reduction technologies.

In order to achieve these goals the following objectives are defined:

1. To identify the characteristics of the flow perturbations that can be introduced into the inner and/or outer regions of the boundary layer to inhibit the drag-generating mechanisms.
2. To determine the potential drag reductions that can be achieved in representative boundary layers by targeting the turbulent structures in the inner and/or outer flow region. Particular attention will be paid to the energy cost and efficiency of the control device.
3. To develop advanced simulation tools and methods to analyse and study turbulent boundary layers at industrially relevant Reynolds numbers.
4. To demonstrate the most promising flow control concepts for turbulence manipulation and skin-friction drag reduction through testing in a wind tunnel.
5. To enable the various concepts to be evaluated at an aircraft level, such that an overall net energy saving can be derived through the incorporation of new simplified Low Order Models into industrial numerical solvers.