Perspectives and Requirements of Numerical Simulation for Future Aircraft Design

In recent years, the aeronautical industry has established numerical flow simulations as a key element in the aerodynamic design process, complementing wind tunnel and flight testing. Consequently, nowadays numerical simulation is already an important cornerstone for aircraft design. The continuous development of physical models and numerical methods and the availability of increasingly powerful computers suggest using numerical simulations to a much greater extent than in the past; radically changing the way aircraft will be designed in the future. In addition to speeding up and improving the product design cycle, numerical simulation provides the possibility to mathematically model all properties of the designed product with their interactions, and to determine the behavior under realistic operating conditions. With suitable high-fidelity multidisciplinary simulation methods at hand, the flight characteristics of an aircraft may be determined through numerical computation, and critical conditions of the flight envelope can be flown virtually before the real first flight is performed. The realization of the vision of an aircraft performing its maiden flight in a virtual computer environment, i.e. flying a virtual aircraft, offers the perspective for a substantial reduction of development risks, and in the medium and long term significant cuts in development costs through stepwise certification. Therefore, considering the future challenges for the aircraft industry, numerical simulation is considered as a key technology for future aircraft design [1], and development and industrialization of advanced simulation are being highly prioritized worldwide, see e.g. [2]. However, today the application of highly accurate methods still is mainly limited to the design point, and the requirements for numerical simulation to further penetrate into design process have to be carefully defined. Focusing on transport aircraft, a review of technological perspectives for aircraft performance enhancement identifies two major challenges: how to efficiently simulate the whole flight envelope, and how to effectively employ numerical simulation in an unknown future hardware environment. Considering the different objectives for performance and loads analysis in aircraft design, requirements with respect to physical simulation and prediction capabilities can be derived. At DLR, these challenges and the associated requirements are being addressed in the framework of the multidisciplinary projects Digital-X (4/2012 6/2016), and its successor VicToria (7/2016 12/2019). Using these activities as an example, an overview of the project objectives are given, and results on enhanced disciplinary methods in aerodynamics and structural analysis, the development of efficient reduced order methods for loads analysis, the development of a multidisciplinary optimization process based on a multi-level/variable-fidelity approach, as well as the development and application of multidisciplinary methods for the analysis of maneuver loads are presented.