Abstract
This paper discusses wind tunnel test results aimed at advancing active flow control technology to increase the aerodynamic efficiency of an aircraft during take-off. A model of the outer section of a representative civil airliner wing was equipped with two-stage fluidic actuators between the slat edge and wing tip, where mechanical high-lift devices fail to integrate. The experiments were conducted at a nominal take-off Mach number of M = 0.2. At this incidence velocity, separation on the wing section, accompanied by increased drag, is triggered by the strong slat edge vortex at high angles of attack. On the basis of global force measurements and local static pressure data, the effect of pulsed blowing on the complex flow is evaluated, considering various momentum coefficients and spanwise distributions of the actuation effort. It is shown that through local intensification of forcing, a momentum coefficient of less than c μ = 0.6 % suffices to offset the stall by 2.4°, increase the maximum lift by more than 10% and reduce the drag by 37% compared to the uncontrolled flow.
Highlights
The design of wing tip devices on civil airliners has changed remarkably in past decades.The conception of wing tip devices dates back more than a century, with the first functioning design patented in 1915 [1] by W
Winglets are designed to minimize the drag during cruise flight. This approach conflicts with performance requirements during low-speed flight when a high-lift system is needed, as the slender shape and high local curvature of modern wing tip devices inhibit the integration of a slat, resulting in early separation at the wing tip at high angles of attack
This optimization conflict might be resolved by active flow control (AFC), as this technology has the potential to augment the overall high-lift system to prevent flow separation where the integration of mechanical devices fails
Summary
The design of wing tip devices on civil airliners has changed remarkably in past decades.The conception of wing tip devices dates back more than a century, with the first functioning design patented in 1915 [1] by W. It was not until the research of Whitcomb [2] 60 years later, triggered by an energy crisis that resulted in the need for better fuel performance, that wing tip devices found their way into practice. Winglets (and all derivatives thereof) are designed to minimize the drag during cruise flight This approach conflicts with performance requirements during low-speed flight when a high-lift system is needed, as the slender shape and high local curvature of modern wing tip devices inhibit the integration of a slat, resulting in early separation at the wing tip at high angles of attack. The suppression of local flow separation is most relevant during the second segment of climb (cf. Federal Aviation Regulations (FAR) Part 25), when the landing gear is retracted and a minimum gradient of climb is prescribed even with one engine inoperative
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
