Flutter Analysis of a Morphing Wing Considering Fluid–Thermal–Structure Coupling

The development of hypersonic morphing aircraft, which alter their shape to optimize performance across diverse flight regimes, introduces significant challenges in predicting and managing aerothermoelastic instabilities. Therefore, a comprehensive flutter analysis of a morphing wing is conducted, systematically evaluating the coupled effects of fluid dynamics, thermal loading, and structural deformation at various extension ratios and temperatures. The investigation reveals that flutter onset is consistently governed by the coupling of the first two structural modes, establishing the primary instability boundary, while a secondary instability pathway involving the third and fourth modes uniquely emerges for the fully extended wing. The critical flutter speed is consistently degraded by both increasing temperature and geometric extension, with these factors exhibiting a coupled effect that exacerbates the stability reduction in high-temperature environments. Furthermore, the flutter frequency displays a non-monotonic relationship with the extension ratio, a trend that is shown to be consistent with the variation of the wing’s free-vibration natural frequencies. These findings provide an essential stability assessment framework for the robust design and flight control of next-generation morphing aircraft.