Experimental Study of an Airfoil with Two Degrees of Freedom in the Low-Subsonic Flow and Compared with Theoretical Results

In this paper, linear and nonlinear analysis of an airfoil with two degrees of freedom in incompressible flow is accomplished for experimental test. Respective equations are extracted by Lagrange's method and used Wagner’s theory to solve this equation in time domain. Two-degree-of-freedom flutter is a combination of bending and torsion vibration modes. A flutter mount system with flexure supports has been developed for flutter tests with rigid wings in wind tunnels. This current study is an experimental investigation into the behaviour of a 2DOF wing section with a flexible structural linearity and nonlinearity support in pitch and plunge motion without free-play. This support system must be providing a well-defined 2DOF dynamical system on which rigid wings can encounter flutter. A classical 2DOF flutter can be described as combination of bending and torsion vibration modes. Evaluation of the results of wind tunnel experiments and effective parameters show that increasing frequency ratio cause the speed of flutter to decrease but it reducedes to minimum value at a frequency ratio and then it increase. Furthermore, it is observed that with increasing the distance center of elastic-axis from leading edge flutter speed decreases.