Assessment of aeroelastic stability of high aspect wing aircraft during the preliminary design

ifasd2024 Tracking Number 7

One concept to reduce an aircraft's fuel consumption is to increase wing aspect ratio. Although such slender wings have low induced drag, a number of aeroelastic issues arise. As an example, high aspect ratio wings are relatively soft in bending and torsion when compared to conventional designs. These structural dynamic properties can lead to a reduction of the flutter speed. In the current research projects VirEnfREI [1] and UP Wing [2], the Institute of Aeroelasticity of the German Aerospace Center performs the aeroelastic stability assessment of transport aircraft configurations equipped with high aspect ratio wings during the preliminary design phase. This paper will compare results of preliminary stability assessments and discuss influences from the structural design on the dynamic behavior of the wings. The in-house simulation-based tool cpacs-MONA [3] is used for the flutter assessment. The aerodynamic and structural simulation models used for the analysis are created by the in-house model generator ModGen [4]. Thus, preliminary but representative models are available which allow a detailed analysis of aeroelastic questions early on in the design process. Both the VirEnfREI and the UP Wing aircraft have the same wing aspect ratio of more than 15, however, they differ in the internal structure of the wing, resulting from different aerodynamic profiles. The dominant structural eigenforms for both configurations are the engine pitching mode (Figure 1, left), coupling with the wing bending mode and the wing torsional mode (Figure 1, right). Figure 1: Engine pitching eigenmode, left, and 1st symmetric wing torsion eigenmode, right, of the VirEnfREI aircraft The initial comparison of the result has shown that the flutter velocity of the UP Wing configuration is higher compared to the VirEnfREI configuration. An important factor for the difference in flutter speed is the increased spar height of the UP Wing configuration, resulting in a stiffer wing in bending and torsion. The engine pitching mode also has found to play a dominant role in those high aspect ratio wing designs, making pylon layout another critical design aspect. In the full paper, a short description of the design and analysis process will be given, followed by a discussion of the influence of the preliminary wing aerodynamic and wing structural designs on the aeroelastic characteristics of the aircraft. References 1. https://www.dlr.de/as/en/desktopdefault.aspx/tabid-18287/29084_read-76559/ 2. https://www.dlr.de/ae/en/desktopdefault.aspx/tabid-19296/31885_read-86706/ 3. M. Schulze, J. Neumann, and T. Klimmek, “Parametric Modeling of a Long-Range Aircraft under Consideration of Engine-Wing Integration” in Aerospace, 8 (1), Page 1-20. Multidisciplinary Digital Publishing Institute (MDPI). ISSN 2226-4310, 2021. 4. T. Klimmek, "Parametrization of Topology and Geometry for the Multidisciplinary Optimization of Wing Structures" in European Air and Space Conference, 2009.