Numerical investigation of nonlinear aeroelastic characteristics of a supersonic drag-reduction spike

The drag-reduction spike is widely employed in the testing of hypersonic vehicles owing to its remarkable ability to reduce drag and heat. Further investigation into the aeroelastic characteristics and mechanisms of the dragreduction spike will offer a valuable reference for the refined design of its aerodynamics and structure. In this paper, based on the in-house high-order accurate CFD/CSD coupling analysis method, the variation law and mechanism of the nonlinear aeroelastic characteristics of the drag-reduction spike under different Mach numbers and dynamic pressures are studied. The results indicate that the nonlinear dynamic response of the dragreduction spike transitions from limit cycle oscillations to more complex oscillatory characteristics as the Mach number increases from 2.0 to 5.0. Simultaneously, it is observed that the amplitude of the structural response also increases correspondingly. The primary factor contributing to this phenomenon is the elevated Mach number, which intensifies the interaction of unsteady aerodynamic loads on the surface of the spike. As a result, the location of the separation points and the structure of the separation vortex on the upper and lower surfaces become significantly asymmetric. Furthermore, as the dynamic pressure increases, the nonlinear dynamic response transitions from a complex characteristic to a stable limit cycle oscillation, accompanied by a corresponding increase in the structural amplitude. In both cases, the dynamical characteristics are mainly dominated by the first-order bending mode, and the vibration frequency remains consistent over time. Besides, the variation law of the flow field with the oscillation of the drag-reduction spike is summarized. As the spike is displaced, the complexity of the separation vortex and the intensity of the reattachment shock wave on the offset side gradually decrease, while the reverse is true on the other side. Meanwhile, a vortex is generated on the blunt body on the offset side of the spike, and the vortex region becomes larger as the offset increases.