Development and Application of Reduced Order Models for Buffeting and Buzz

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The determination of the limits of the flight envelope is a major task in aircraft design and analysis. In this regard, aeroelastic phenomena occur that are characterized by the coupling of aerodynamic, structural-elastic and inertial forces. In addition to the self-induced excitation (flutter), dynamic response problems such as buffeting and buzz are of particular importance. For efficiency reasons, the unsteady flow simulations are mainly carried out using potential theory methods. These approaches, however, cannot predict the aerodynamic characteristics of the transonic flight regime adequately since aerodynamic nonlinearities induced by shocks an flow separation are not reproduced. In contrast, the unsteady aerodynamic forces can be determined with sufficient accuracy using state-of-the-art CFD (computational fluid dynamics) methods. This advantage, however, comes along with a drastic increase of the computational costs, which cannot be met with today's capacities for the huge amount of calculations needed for the aeroelastic analysis process. One way to limit the computional effort is to use Reduced Order Models (ROMs) that are conditioned and calibrated using selected CFD simulation data. A ROM is denoted as a simplified model that efficiently reflects the dominant characteristics of the underlying system. The goal of this project is the development of a novel nonlinear ROM method, which can be used to address transonic buffeting and buzz. For this purpose, the validated ROM methodology designed for flutter predictions has to be expanded in order to capture the unsteady aerodynamic mechanisms related to buffet and buzz. As a consequence, the integral forces and moments or generalized aerodynamics forces can be computed by the ROM, which leads to a significant acceleration of unsteady aerodynamic and aeroelastic analyses.