[home] [Personal Program] [Help]

---

Session: Poster session & drinks
Session starts: Tuesday 18 June, 18:00
Presentation starts: 18:03
Room: Room 1.1

---

Zhiying Chen (Beihang University)
Yang Meng (Beihang University)
Zhiqiang Wan (Beihang University)
Changchuan Xie (Beihang University)
Chao Yang (Beihang University)

Abstract:
Highly flexible wings of large aspect ratio are commonly found in high-altitude long-endurance aircraft, large deformations of such wings can lead to structural and aerodynamic nonlinearity, which includes geometric nonlinearity and stall. The relation between structural nonlinear force and stall aerodynamics affects the post-flutter behaviour of the wing. Although there has been a significant amount of work on post-flutter analyses, post-flutter constraints, which are critical for preventing undesirable subcritical limit cycle oscillations, have been rarely considered in design optimization. In this paper, the structural optimization of a clamped high-aspect-ratio highly flexible wing with post-flutter constraint is presented. Firstly, a nonlinear unsteady aeroelastic model is built by coupling nonlinear structural and aerodynamic model. Strain-based beam theory is used for efficient structural modelling, and strip theory combining the ONERA dynamic stall model is used for aerodynamic modelling. Then, the equilibrium position for a specific angle of attack is solved, and the flutter speed is determined by performing an eigenvalue analysis of the linear equation at the equilibrium position. The nonlinear perturbation solution near the flutter speed is calculated using the method of multiple scales, from which a scalar variable can be extracted to dictate the characteristic of the limit cycle. Finally, several design variables which controls the stiffness and inertia characteristics are defined, and the gradient-based optimization is carried out under flutter, post-flutter and other constrains. The results shows that the current methods employed can accurately and efficiently calculate the nonlinear characteristics of the system, meeting the requirements for design optimization. And through optimization, the limit cycle can be transformed from subcritical to supercritical, which ensures the effectiveness of the flutter constraint.