Numerical Analysis of Jet Engine Perturbations on the Buffet Phenomenon

机翼上的跨音速流的特征是出现局部超音速流区，这些超音速流区由激波终止，激波的强度随自由飞行马赫数和迎角的增加而增加。在足够的强度以上，激波引起气流分离，在某些飞行条件下，由于分离流和激波之间的相互作用，气流分离导致自激周期性激波振荡，这被称为抖振。抖振现象为整个飞行稳定性定义了一个极其关键的载荷状态。由于虚拟飞行试验的重要性日益增加，而且必须对基本支承结构的重量进行最佳化，因此必须准确地预测和详细地了解流场扰动对抖振的发生和存在的影响。由于生态和经济驱动的现代更有效的超高涵道比发动机（超高涵道比）的发展，其直径不断增加，并且它们明显靠近机翼，发动机喷流和机翼上的气流之间发生了更强的非定常复杂相互作用，这对于发动机的气动集成非常重要。 在TP 1范围内，将分析UHBR发动机一体化所引入的扰动的影响，特别是由热堆芯和冷旁路流组成的相关发动机喷流的影响。研究的一个重要部分是分析后缘附近气流产生的声场，这是已建立的抖振模型的核心要素，并受到发动机集成的显著影响。为了量化这种影响，高分辨率的模拟流场和由此产生的声场上执行的空中客车XRF-1配置在飞行相关的雷诺数。为此，一个直接耦合的方法，包括壁模拟的大涡模拟和声扰动方程的同时解决方案。对于详细的动态分析，TP 1特别依赖于经验模式分解。这种方法没有预先假设所研究的动力学的数学形式，因此特别适合于分析抖振现象背后的高度非线性跨音速流场。模拟是在与项目合作伙伴和伴随的ETW测量活动的密切合作下进行的。因此，项目合作伙伴之间不断交流数据和知识，以便对抖振现象进行连贯和复杂的调查。

The transonic flow over wings is characterized by the occurrence of local supersonic flow regions which are terminated by a shock wave the strength of which increases with freestream Mach number and angle of attack. Above a sufficient strength, the shock wave induces flow separation which under certain flight conditions due to the interaction between the detached flow and the shock wave results in self-excited periodic shock oscillations, which are denoted buffet. The buffet phenomenon defines an extremely critical load state for the overall flight stability. Regarding the ever-increasing importance of virtual flight tests and the necessary optimization of the weight of the essential supporting structure, it is essential to exactly predict and to understand in detail the impact of perturbations in the flow field on the onset and existence of buffet. Due to the ecologically and economically driven development of modern, more efficient UHBR-engines (Ultra-High Bypass Ratio) with increasing diameter and their pronounced vicinity to the wing, stronger unsteady intricate interactions between the engine jet and the flow over the wing occur which are significant for the aerodynamic integration of the engine. Within the scope of TP1, the influence of the disturbances introduced by the integration of a UHBR engine and, in particular, the influence of the associated engine jet consisting of the hot core and the cold bypass flow will be analyzed. An essential part of the investigations is the analysis of the acoustic field resulting from the flow in the vicinity of the trailing edge, which is a central element of established buffet models and is significantly influenced by the integration of the engine. To quantify this influence, highly resolved simulations of the flow field and the resulting acoustic field are performed on the Airbus XRF-1 configuration at flight-relevant Reynolds numbers. For this purpose, a directly coupled approach consisting of wall-modeled large-eddy simulations and the simultaneous solution of the acoustic perturbation equations is followed. For the detailed analysis of the dynamics, TP1 in particular relies on empirical mode decomposition. This method makes no prior assumption regarding the mathematical form of the investigated dynamics, and thus is particularly well suited for the analysis of the highly nonlinear transonic flow field underlying the buffet phenomenon. The simulations are carried out in close cooperation with the project partners and the accompanying ETW measurement campaign. Thus, there is a constant exchange of data and knowledge between the project partners to conduct a coherent and complex investigation of the buffet phenomenon.