Transonic Flutter Prediction Using the Transonic Doublet Lattice Method and a Comparison with the Field Panel Method.

For assessment of the applicability of the Transonic Doublet Lattice Method (TDLM) to transonic flutter prediction, the flutter boundary of the semi-span Aeroelastic Model Program (AMP) flutter model is calculated. The results show that the transonic flutter dip can be predicted and that the flutter boundary compares well with test results. A parameter study of panel numbers in chordwise and spanwise directions is made, showing that the convergence behavior of the TDlM is very good.A sufficiently accurateflutter result can be obtained at economic costs. A comparison of thefield Panel Method (FPM) and the TDLM is made. Results of transonic unsteady aerodynamics of a rectangular wing, the Northrop F-5 wing, and the LANN wing in pitching oscillation are compared, and the agreement is good. The transonic flutter results of a semi-span AMP flutter model are also compared. Flutter results show that the TDLM has a better agreement with experimental results than the FPM. The convergences of flutter results with spanwise panel numbers are similar, but the convergences with chordwise panel numbers differ considerably, and the TDLM is much better than the FPM. Some further analyses are made. Results show that the TDLM keeps the advantages of both the DLM and the FPM, now providing an accurate and economic unsteady transonic aerodynamic calculation tool for routine transonic flutter calculation. The TDLM also has some attractive advantages because of its further extension to non-planar configurations