Stall Flutter Control Of High-aspect Ratio Light-weight Wing

Since the appearance of airplane, it has always accompanied with aero-elastic problems. Many aviation accidents have been caused by the problems of aerodynamic elasticity. In recent years, due to the advantages of the High Altitude Long-Endurance(HALE) solar aircraft in the applications of military and civilian, it has been paid much attention. To extend the maximum flying distance of the solar airplane, this kind of aircraft usually employs high-aspect ratio light-weight wings that enable to effectively absorb solar energy to empower aviation. High-aspect ratio light-weight wing is very flexible, and its poor aero-elastic performance may induce severe flutter problems. The technology of Active Aeroelastic Wing(AAW) design was put forward to overcome the contradiction between the plane lightweight and insufficient stiffness. This technique imposes the feedback force, produced by an active control system according to the deformation of wing caused by aerodynamic effect, onto the wings to make them appear a desirable deformation or movement. Enlightened by AAW techniques, we can use synthetic jets to control the fluid field around the wings and further to influence the aero-dynamic loads on the wings, eventually to suppress flutter of aircraft.This thesis first discusses various aerodynamic loads possibly encountered during the aircraft taking-off and in cruise state, including the sudden wind, turbulence, the fluctuating aerodynamic load at large angle of attack when aircraft involves the troposphere and steady aerodynamic load when aircraft is in cruise state. The methods for modeling these aerodynamic loads are elaborated. Based on the analysis of aerodynamic load, a three-dimensional mathematical model is developed for simulating aerodynamic response of high-aspect-ratio wings by using the theory of the thin-walled beam with closed sections and the Hamilton's principle and the Grossman quasi-steady aerodynamic model. The Galerkin method was used to solve the model. We discussed the static deformation, torsion divergence, flutter and sudden wind, turbulence response of wings, drawing some meaningful conclusions. To study the stall flutter suppression of the wing by active control flow using synthetic jets.We use simulation software FLUENT to study the flow field around E214 airfoils under different angle of attack, the influence of angle of attack on aerodynamic load characteristics was analyzed, and the formation mechanism of fluctuating aerodynamic loads and its frequency characteristic under large angle of attack were investigated. By numerical simulations of the flow field around E214 airfoils when adding synthetic jet in different angle of attack, the influence of the synthetic jet on aerodynamic load was addressed. As for the stall flutter suppression of the wing under lardge angle of attack using synthetic jets to control the frequency and phase of aerodynamic load, especially taking 18 ° angle of attack as an example, the pulse frequency control and phase control of the synthetic jet on aerodynamic load were studied, and the frequency-speed range of the synthetic jet for achieving the frequency control and phase control was obtained.