The effect of longitudinal atmospheric turbulence on the flutter and post-flutter dynamics of a two-dimensional airfoil with a structural nonlinearity is investigated. The particular structural nonlinearity considered is a hardening cubic stiffness in torsion. The aerodynamic flow is considered as incompressible and to remain attached; hence, the aerodynamics is represented in a linear manner. For the so called nonexcited case, corresponding to zero turbulence, two distinct regions of dynamic response are obtained. For velocities below the flutter point the airfoil response is characterized as a stable equilibrium position, while after the onset of flutter, limit cycle oscillations, LCOs, occur. However, contrary to the nonexcited case, three different regions of dynamic behaviour are observed when the airfolil is excited by longitudinal turbulence. For the first and third regions, corresponding to the lowest and highest ranges of velocity respectively, the dynamic response is the same as that obtained for the nonexcited case for velocities less than or greater than the flutter velocity. However, in the middle range of velocities a new form of dynamic behaviour is obtained, where the airfoil response is concentrated about the equilibrium position. The existence of three regions of dynamic behaviour, as opposed to two for the nonexcited case, is attributed to the parametric nature of the excitation. For this excited case the flutter point and onset of LCOs no longer coincide. Furthermore, flutter occurs at a lower velocity than that obtained for the nonexcited case, while the onset of LCOs occurs at a higher velocity.
A numerical investigation of the stability and post-flutter response of a 2D nonlinear airfoil in longitudinal atmospheric turbulence
Numerische Untersuchung der Stabilität und der Nachflatterreaktion eines nichtlinearen, zweidimensionalen Tragflügels in atmosphärischer Längsturbulenz
1996
11 Seiten, 9 Bilder, 26 Quellen
Conference paper
English
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