Numerical investigation on transonic flutter characteristics of an airfoil with split drag rudder

• Analyzed the effect of split drag rudder (SDR) on the transonic flutter characteristic of rigid NACA 64A010 through numerical simulations. • The increase of the split angle has a positive influence on flutter speed in the subsonic state, where the flutter velocity increases by approximately 80% with a split angle increase in the range 0–10 deg. • The SDR delays the shock wave shifting downstream, and the Mach number corresponding to reaching freeze region increases as the split angle increases, which leads to the delay in the occurrence of the transonic dip. In this paper, a series of flutter simulations are carried out to investigate the effects of split drag rudder (SDR) on the transonic flutter characteristic of rigid NACA 64A010. A structural dynamic model addressing two-degree-of-freedom pitch-plunge aeroelastic oscillations was coupled with the unsteady Reynolds-averaged Navier-Stokes equations to perform flutter simulation. Meanwhile, the influence mechanism of SDR on flutter boundary is explained through aerodynamic work and the correlated shock wave location. The results show that the SDR delays the shock wave shifting downstream, and the Mach number corresponding to reaching freeze region increases as the split angle increases. Therefore, the peak value of aerodynamic moment coefficient amplitude and the sharp ascent process of phase occurs at higher Mach number, which leads to the delay in the occurrence of the transonic dip. Besides, before the transonic dip of airfoil without SDR occurs, the aerodynamic moment phase of airfoil with the SDR decreases slowly due to the decrease in the speed of shock wave moving downstream. This results in an increased flutter speed when employing the SDR before the transonic dip of airfoil without SDR occurs. Meanwhile, the effects of asymmetric split angles on the transonic flutter characteristics are also investigated. Before the transonic dip of airfoil without SDR occurs, the flutter characteristic is dominated by the smaller split angle. Flutter boundary for the Isogaicase with different split angles