Development and Application of Reduced Order Models for Buffeting and Buzz

飞行包线极限的确定是飞机设计和分析中的一项主要任务。在这方面，出现了气动弹性现象，其特征是气动、结构弹性和惯性力的耦合。除了自激(颤振)外，抖振和嗡嗡声等动力响应问题也尤为重要。由于效率的原因，非定常流动的模拟主要采用势流理论方法。然而，这些方法不能很好地预测跨音速飞行状态的气动特性，因为不能再现由激波和流动分离引起的气动非线性。相比之下，使用最先进的CFD(计算流体动力学)方法可以足够精确地确定非定常气动力。然而，这种优势伴随着计算成本的急剧增加，这是当今气动弹性分析过程所需的大量计算能力无法满足的。限制计算工作量的一种方法是使用降阶模型(ROM)，这些模型使用选定的CFD模拟数据进行调节和校准。只读存储器被表示为有效地反映底层系统的主导特征的简化模型。这个项目的目标是开发一种新的非线性只读存储器方法，可以用来解决跨音速抖动和嗡嗡声。为此，必须扩展用于颤振预测的已验证的只读存储器方法，以便捕捉与抖振和嗡嗡声相关的非定常气动机制。因此，该程序可以计算积分力和力矩或广义气动力，从而大大提高了非定常气动力和气动弹性分析的速度。

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.