An analysis of ground effects on aerofoil flutter

Abstract

A new transport system : "Aerotrain" has been recently proposed. It has wings and flies close to ground along a guide way of an open channel. The aerodynamic characteristics of the wing are strongly affected by the ground. In order to elucidate the aerodynamic stability of the aerotrain wing, it is necessary to analyze the ground effects on the unsteady aerodynamic forces and flutter speed. In this paper, the aerodynamic forces and moments on the two dimensional aerofoil are analyzed in the assumption that it is in the proximity to the ground and oscillating in the incompressible flow. The equation of motion of the aerofoil is derived by considering the balance of the inertia, elastic, aerodynamic, and exciting forces. The flutter speeds are obtained by the U-g methods considering a structural damping. The flutter speed is decreased as the center of gravity is shifted to backwards from the pitching axis, when it is close to the ground.