Flutter dynamic pressure at the transonic region is much lower than that at other regions. However, the transonic flutter boundary is difficult to predict because of the nonlinear effects induced by the shock wave and separation of boundary layers. In particular, the prediction precision with the doublet lattice method, which is often used in practice, is reduced remarkably at the transonic region. Therefore, in the framework of the Reynolds-Averaged Navier-Stokes solver, a time-domain flutter analysis method is established, where generalized equations for structural motion are developed based on structural modes, a method for interpolation of mode shapes is proposed via the radial basis function, and an efficient mesh deformation method is constructed by combining the radial basis function with transfinite interpolation. The time-domain flutter analysis method is validated by the AGARD445.6 wing. However, the time-domain method is solved by the time-marching strategy, consuming numerous computational resources and time. To improve efficiency of flutter prediction, a frequency-domain flutter analysis method is proposed, where the aerodynamic coefficient matrix is calculated efficiently by the High-Order Harmonic Balance(HOHB) method, and relates mode displacements and generalized forces in the frequency-domain. The frequency-domain method proposed is validated by two-dimensional and three-dimensional test cases. It is illustrated that the HOHB method can increase the prediction efficiency by 6 times without deteriorating the prediction precision obviously.
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