Nonlinear aeroelastic characteristics of an all-movable fin with freeplay and aerodynamic nonlinearities in hypersonic flow

Nonlinear aeroelastic characteristics of an all-movable fin in hypersonic flow is investigated considering both aerodynamic and freeplay nonlinearities. The unsteady aerodynamic model is developed by the third-order piston theory for accurately obtaining nonlinear aerodynamic loading of all-movable fin with thickness ratio of airfoil, angle of attack and sweep angle. An equivalent temperature model is used to evaluate the effects of aerodynamic heating on structural stiffness and aeroelastic behaviors. The results demonstrate that the temperature elevation is an important parameter that can reduce the flutter boundary and extend the region of chaotic motions. In the observation of limit cycle oscillations (LCO) and evolution of dynamic bifurcation, aerodynamic nonlinearity produces a smaller amplitude response compared with linear piston theory, but has no apparent influence on dynamic bifurcation. When free-plays both in pitch and flap degrees-of-freedom (DOFs) are further considered, the system exhibits more complex bifurcation behaviors, especially the existence of quasi-periodic and chaotic responses in low Mach number range. Chaotic motions are predicted by mean of the Poincare maps and the evolution of the largest Lyapunov exponent. Moreover, the numerical results also show that the nonlinear aeroelastic behaviors are significantly affected by some parameters, such as freeplay magnitude, thickness ratio and sweep angle.