Enhanced DLM Flutter Analysis via Viscous Panel-Method-Based Aerodynamic Corrections

Accurate prediction of transonic flutter using simulation remains a challenge through the aircraft design process due to the nonlinear flow phenomena near Mach 1 and the computational expense of high-fidelity CFD methods. This paper introduces a correction methodology that enhances the accuracy of doublet lattice method (DLM)-based flutter analysis by leveraging aerodynamic data from FlightStream®, a surface-vorticity, panel-method flow solver capable of modeling compressible, viscous flows. The correction is implemented in OptiStruct® via diagonal scaling factors (Wkk) applied to the aerodynamic influence coefficient matrices. These factors are derived by calibrating the lift and moment slopes of DLM against those obtained from static FlightStream® simulations, assuming a quadratic form for the moment distribution across each wing strip. The methodology is validated against the AGARD 445.6 wing benchmark, where the corrected flutter speeds show significantly improved agreement with experimental data. At Mach 0.901, the flutter speed prediction error is reduced from 5.2% to 0.3%, demonstrating the effectiveness of the proposed aerodynamic correction scheme for transonic flutter prediction using low-order methods.