Aeroelastic behaviour of a wing with over-the-wing mounted UHBR engine
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ORIGINAL PAPER
Aeroelastic behaviour of a wing with over‑the‑wing mounted UHBR engine N. Neuert1 · D. Dinkler1 Received: 10 January 2020 / Revised: 18 June 2020 / Accepted: 19 August 2020 © The Author(s) 2020
Abstract The aeroelastic behaviour of a wing with an over-the-wing pylon-mounted ultra-high bypass ratio engine and high-lift devices is studied with a reduced-order model. Wing, pylon and engine structures are reduced separately using the modal approach and described by their natural frequencies and modes. The characteristic aerodynamic loads are investigated with steady and unsteady flow simulations of a two-dimensional profile section. These results indicate possible heave instabilities at strongly negative angles of attack. Three-dimensional effects are taken into account using an adapted lifting line theory according to Prandtl. Due to high circulations resulting from the high-lift systems, the effective angles of attack are in the range of the potential instabilities. The substructures and aerodynamic loads are coupled in modal space. For the wing without three-dimensional effects, the bending instability occurs at the corresponding negative angles of attack. Even though there is potential for improvement, including the three-dimensional effects shifts the endagered area to possible operation points. Keywords Reduced-order model · Aeroelasticity · High-lift · Aerodynamics
1 Introduction The number of flights is continuously increasing. To shorten the journey and ease the traffic at large airports, small existing airports are taken into consideration. Since these airports are often close to populated areas, fuel and noise emissions must be reduced. Due to short runways, the aircraft must also be designed for short take off and landing. The reference aircraft shown in Fig. 1 was designed by the Coordinated Research Centre (CRC) 880 [18, 19]. The wing has a halfspan of 14.37 m, a leading-edge sweep angle of 26◦ , a taper ratio of 0.32, and a dihedral angle of 3◦ . Noise reduction is realised by an over-the-wing mounted ultra-high bypass ratio (UHBR) engine [3]. High-lift is achieved with both passive and active systems. The active system, the Coandă flap, is a combination of a trailing edge flap and a thin jet, described by its momentum coefficient
* N. Neuert n.neuert@tu‑bs.de D. Dinkler d.dinkler@tu‑bs.de 1
TU Braunschweig, Institute of Structural Analysis, Beethovenstr. 51, 38106 Brunswick, Germany
c𝜇 =
ṁ jet vjet q∞ Aref
.
(1)
It describes the ratio of introduced jet momentum per time at the jet exit section ṁ jet vjet to the freestream dynamic pressure q∞ and the wing reference area Aref . According to the Coandă effect [24] the thin jet is blown out upstream of the flap to deflect the flow to follow the curved surface. This leads to an increase in lift, which has been investigated extensively [5–7, 9, 11, 16, 23]. As a side effect, a suction peak can be observed at the leading edge, which is decisive for the stall behaviour [1]. To reduce the suction peak at the so called clean nose
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