School of Mechanical Engineering Michael Lahutin
School of Mechanical Engineering Seminar
Wednesday, April 19, 2017 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
Active Flow Control of Wing-tip Flow Separation
Michael Lagutin
MSc Student of Prof. Avraham Seifert
School of Mechanical Engineering, Tel Aviv University, 69978 Tel Aviv, Israel
High-Lift devices, such as leading-edge slat, are commonly used in aerodynamics for increasing airfoil and wing performance at high incidence angles, mainly for takeoff and landing. However, due to complexity, weight, and cost of the deploying mechanism, the slat is not covering the full span of the wing, thus leaving the tip region “unprotected.” The slat termination creates slat-edge vortices that impinge upon the upper wing surface. The slat-edge-generated stream-wise vortices are negatively affecting the performance of the outer wing portion, resulting in local flow separations that reduce lift and significantly increase drag.
The current study deals with this problem, and was performed on an industry relevant geometry, in collaboration with Israel Aerospace Industries (IAI) and Airbus as part of the AFLONEXT EU FP7 project. The motivation of the work is to increase the robustness of the wingtip design at take-off conditions, while improving the aerodynamic efficiency at cruise conditions by closer to optimized design. The experimental model is a 3D high-lift wing configuration, which consists of swept-back (by 25°) wing with trailing edge flap fixed at 20°, leading edge slat and rounded wing tip. Active flow control (AFC) is used to delay the wingtip stall, thus improving the lift to drag ratio and allowing a steeper climb gradient. The AFC configuration was chosen based on previous studies and CFD results obtained by IAI. The work focused on steady suction AFC method, its effect was investigated through wind tunnel tests. Experiments consisted of pressure map acquiring, near wake 3D scans and a use of flow visualization techniques.
It was shown, that AFC application can delay stall, increase lift and reduce drag on the “unprotected” (by the slat) wing-tip region. The results were compared and mutually validated by CFD data obtained by IAI. It is expected that cruise optimized wingtip design will be able to provide an improvement in aerodynamic efficiency with a net benefit in fuel consumption and emissions up to 2%.
