Prediction of Aircraft Dynamic Stability Derivatives Using Time-Spectral Computational Fluid Dynamics

Abstract

In this study, the dynamic stability derivatives of an aircraft model are calculated using CFD for the forced-pitch oscillation. The time-spectral, or reduced-frequency, method has been developed for RANS simulations on unstructured grids. It achieves faster computations than the time-marching method for periodically unsteady flows. The efficiency and accuracy of the method are first validated through comparisons with the transonic experiment of a pitching LANN wing. Next, the longitudinal dynamic-stability derivatives of a simplified aircraft model are calculated. Dependency of the damping-in-pitch and oscillatory longitudinal stability on the Mach number agreed reasonably well with the experimental results. Both the instantaneous flow field and frequency characteristics obtained directly from the time-spectral results are discussed to determine the effect of Mach number on the stability derivatives.