Single-mode flutter analysis of drag reduction spike by parameterized eigenvalue method and energy method

Attaching a spike to the blunt nose of a vehicle is one of the simplest ways to reduce drag in supersonic and hypersonic conditions. However, the spike can encounter aeroelastic instability which remains a challenging topic and limits applications in practical engineering. Computational fluid dynamics/computational structural dynamics coupling method is used and the results show the spike can experience flutter at low structural stiffness ratios and the flutter is dominated by a single mode. To evaluate the effects of structural parameters efficiently, this paper proposes a parameterized eigenvalue method by deriving the parameterized reduced structural equation which is coupled with an aerodynamic reduced order model. Results show both the critical flutter frequency and the critical natural frequency decrease with the increase of structural damping ratio and the flutter frequency is close to the natural frequency only for large mass ratios. It is found that the critical flutter frequency does not change with the mass ratio for zero structural damping, but this is not true for non-zero structural damping. This paper also proposes an energy method based on the work-energy principle and the aerodynamic frequency response function. The energy method can also obtain the critical flutter frequency and can explain how the structural parameters influence the flutter characteristics.