FLUTTER CONTROL OF AN AIRFOIL WITH CAMBER MORPHING NEAR GROUND

Abstract

This paper presents the numerical investigation of the flutter control via the camber morphing of an airfoil under the ground effect. An aircraft experience a significant change in the aerodynamic characteristics while flying near the ground due to the ground effect phenomenon. As a consequence, there is a negative effect on the flutter instability. Studies have shown that the wing in proximity to the ground tends to destabilize the wing at a lower speed with an exponential decrease in flutter speed when the height above the ground is decreased. Flutter at lower speeds on the wing is undesirable as this limits the flight envelope and could lead to structural failures. In most cases, delaying the flutter using the flutter suppression technique becomes significant. Therefore, this paper focuses on the suppression of flutter via camber morphing complemented by a proportional differential (PD) controller. In this paper, the nonlinear system is represented by a typical airfoil system, elastically supported in a potential flow near the ground. Dynamic equations of motion are formulated using Lagrange's equation and flow around the airfoil is modeled using the unsteady discrete vortex method. The ground effect is simulated using the mirror-image method. The aeroelastic equations of motion are constructed in a state-space form and solved explicitly using a predictor-corrector numerical scheme. The numerical results are presented to demonstrate the ability of a simple PD controller to suppress unstable flow-induced vibrations near ground.