Aeroelastic Behavior of Two Airfoils in Proximity

Abstract

This paper investigates the aeroelastic behavior of elastically supported airfoils due to structural and aerodynamic coupling effects between them in an incompressible uniform flow. The flow is modeled based on a potential theory for thick and thin airfoils considering the coupled interference effect. Coupled aeroelastic equations of motion are formulated in a state-space form and solved explicitly using a predictor-corrector scheme. The numerical analyses are presented for airfoils in proximity with and without structural coupling. It is shown that the airfoils in proximity oscillate out of the phase and destabilized the airfoils at lower speeds. The closer the airfoils are, the lower the speed at which flutter instability occurs. Also, the interference effect becomes more significant on reducing the flutter speed for thick airfoils in proximity. For structurally coupled airfoils, the flutter instability occurs at lower speeds for the lower coupling stiffness value. It is further worsened in the presence of aerodynamic interference. Although, for a larger stiffness value, the flutter instability could be delayed in the presence of aerodynamic interference. This study finds that the lifting surfaces in proximity without structural coupling can become unfavorable in the aeroelastic design. The results provide preliminary insights into the coupled structural and aerodynamic interference effects on the flutter instability for a multiple lifting surface configuration.</p>