Study On Hypersonic Control Surface Flutter Wind Tunnel Test And It's Numerical Simulation

Flutter is a self-oscillating phenomenon of the elastic aircraft structures interacted with the aerodynamic forces,which lead to serious risks to flight safety.Flutter is thus one of the most important issues that should be considered in the aircraft design.For the hypersonic flight vehicles,it is imperative to accurately obtain their flutter characteristics.However,previous research work related to flutter has not yet complete and some issues were still needed to be considered: deficient theoretical methods for wind tunnel test,difficult model fabrication,and imperfect protection technology.In addition,the accuracy of numerical simulation was influenced by the shock boundary layer interaction and the real gas effects,etc.According to the above issues,in this paper the following work was presented:The flutter test of a hypersonic control surface model with Mach number 5 was carried out.The flutter process from stability to divergence was reproduced in the wind tunnel.The test results showed that the flutter dynamic pressure was 29.5kPa and the flutter frequency was 29.3Hz;moreover,the flutter pattern was the first-order modal coupling of bending and torsion.It was also found that hypersonic aeroelastic characteristics was sensitive to the structural modal shapes.A numerical simulation was outlined for the above test model.Various aerodynamic models and coupled iterative strategies were used to predict the flutter using the time-domain and the frequency-domain methods,respectively.The results indicated that the flutter dynamic pressures predicted using the third-order piston theory,the uniform lifting surface theory,Euler and N-S equations had good agreements,and the errors between the computational and experimental results were less than 7%.The error of the loose coupling method was more than 15% using the time-domain method.Meanwhile,it was also revealed that the supporting mechanism resulted in the shock wave boundary layer interference effect,which increased the flutter pressure to some extent.The theoretically predicted results became closer to the experimental results if considering this influential factor.For the two-dimensional double wedge airfoil at the altitude of 10 km and the Mach number of 5,the flutter dynamic pressure under various modal shapes was predicted with the aid of the matrix perturbation theory and the Euler equations.The results indicated that the flutter dynamic pressure of the wedge airfoil leading edge is abnormally sensitive to the modal shapes at hypersonic flow.The corresponding flutter dynamic pressure was increased by 9.4% and 21.6% when the modal shapes at the sensitive positions were enlarged by 5% and 10%,respectively.The present work can provide a useful reference for the design of hypersonic flight vehicles.