This paper extends the dual equivalent linearization technique (ELT) to obtain flutter speeds of a two-dimensional airfoil with nonlinear stiffness and damping in pitch degree of freedom. Although the use of dual ELT has been investigated in some previous papers, this paper presents an extension of dual ELT using the global-local approach, in which the local equivalent linearization coefficients are averaged in the global sense. | Vietnam Journal of Mechanics, VAST, Vol. 37, No. 3 (2015), pp. 217 – 230 DOI: EXTENSION OF DUAL EQUIVALENT LINEARIZATION TECHNIQUE TO FLUTTER ANALYSIS OF TWO DIMENSIONAL NONLINEAR AIRFOILS Nguyen Minh Triet VNU University of Engineering and Technology, Hanoi, Vietnam ∗ E-mail: 4triet@ Received June 26, 2015 Abstract. This paper extends the dual equivalent linearization technique (ELT) to obtain flutter speeds of a two-dimensional airfoil with nonlinear stiffness and damping in pitch degree of freedom. Although the use of dual ELT has been investigated in some previous papers, this paper presents an extension of dual ELT using the global-local approach, in which the local equivalent linearization coefficients are averaged in the global sense. The numerical calculation shows that the extended dual ELT gives more accurate flutter speeds in comparison with the ones of classical ELT. Keywords: Airfoil flutter, dual equivalent linearization technique, global-local approach, limit cycle oscillation, nonlinearity. 1. INTRODUCTION The most dramatic physical phenomenon in the field of aeroelasticity is flutter, a dynamic instability which often leads to catastrophic structural failure. Classical theories of linear flutter have been presented for a long time [1, 2]. However, the real system exhibits the nonlinear behavior due to the control mechanisms or the connecting parts between wing, pylon, engine, external stores or the large deflection. Nonlinear airfoil flutter is a typical self-excited vibration with rich nonlinear dynamical behaviors, such as limit cycle oscillation (LCO), bifurcation and chaos [3]. Nonlinear aeroelasticity has been a subject of high interest the literature is now extensive [4, 5], in which many issues are still under active investigation. In the context of nonlinear aeroelasticity, a LCO is one of the simplest dynamic bifurcations but is a good general description for many nonlinear aeroelastic behaviors. .
