DEVELOPMENT OF METHODS FOR MULTIDISCIPLINARY WING DESIGN AND OPTIMIZATION UNDER LOAD ALLEVIATION

Abstract

This study will present the efforts expended during DLR’s internal project oLAF (Optimal Load-Adaptive Aircraft) within the main working package HAP4. On the one hand, this work package focuses on the further development of a multidisciplinary design optimization (MDO) chain, and on the other hand it included activities on exploring novel methods that can enrich and enhance the multidisciplinary aircraft design process. The activities on the MDO chain cover two targets on methods development. The first target lies in improving and sharpening the existing cross-institute multidisciplinary aircraft design tools by adding new technologies and applying them to a new configuration. The second target focuses on extending the tools’ capabilities towards dealing with load alleviation during the automatic multidisciplinary wing design process. DLR’s cross-institute gradient-based multidisciplinary design optimization (MDO) chain is presented in Figure 1. It involves mainly two parts; the first ensures the structure integrity and the second predicts and improves the flight performance, mainly at cruise and off-design points. The structure integrity is handled via the Structure Loads and Sizing and Flutter Analysis components shown in Figure 1. The flight performance is predicted here via coupling a RANS-based flow solver (DLR’s TAU) with the structure solver NASTRAN in order to account for the elastic deformations the aircraft undergoes, and with the 1D thermodynamic engine model, to exchange thrust and engine boundary conditions while trimming the aircraft forces. The shape improvement is predicted based on the design sensitivities, which require a differentiation of the numerical models engaged. On the structure integrity side, two main aspects were pursued. The first one was to model the structure via composite materials, either while dealing with it as a smeared thickness or while giving the designer more freedom to tackle the different layers nearly independently. The second aspect was to enhance the loads prediction process with load alleviation tools that allow the designer to investigate the feasibility of such systems in a robust and automatic design process. On the flight performance side, the focus lied on enhancing the aircraft trim process, while engaging the sizing of the engine and all the modelling complexities related to that, in the design loop. The final paper will present design optimization studies and investigations that highlight the new developments and analyze the outputs correspondingly.