POST-INSTABILITY BEHAVIOR OF A STRUCTURALLY NONLINEAR AIRFOIL IN LONGITUDINAL TURBULENCE

The effect of longitudinal atmospheric turbulence on the dynamics of a n airfoil with a hardening cubic structural nonlinearity in pitch is i nvestigated. The aerodynamics is taken as linear, For the so-called no nexcited case, corresponding to zero turbulence, two distinct regions of dynamic response are obtained. For velocities below the nutter spee d, the airfoil response is characterized as a stable equilibrium posit ion; whereas after the onset of flutter, limit cycle oscillations occu r, However, three different regions of dynamic behavior are observed w hen the airfoil is excited by longitudinal turbulence, For the lowest and highest ranges of velocity, the dynamic response is the same as th at obtained for the nonexcited case, However, in the middle range of v elocities, a new form of dynamic behavior is obtained, where the airfo il response is concentrated about the equilibrium position, The existe nce of this new region of dynamic behavior is attributed to the parame tric nature of the excitation, In addition, for the excited case, flut ter occurs at a lower velocity than for the nonexcited case; whereas t he onset of limit cycle oscillations occurs at a higher velocity.