Preliminary Structural Design of a High Aspect Ratio Transport Aircraft With Laminar Wing

A high aspect ratio jet transport aircraft with a laminar wing is designed within the project ULTIMATE funded by the German Federal Aeronautical Research Programme. The design of the wing features both a high aspect ratio (> 15) as well as a laminar airfoil layout with natural laminar flow (NLF) realized by a particular leading edge shape to obtain Crossflow Attenuated Natural Laminar Flow (CATNLF) in the inner region of the wing. A particular challenge is the structural design and optimization of this wing due to the impact of static and dynamic aerodynamic and aeroelastic effects, which must be considered throughout the whole design process. In this work we present an approach for the generation and assessment of the structural model based on aeroelastic models of mixed fidelity (potential aerodynamics as well as CFD) which are derived from a prescribed aerodynamic (flight) shape of the wing. For the structural optimization of the wing, load cases requested by the CS-25 specifications (including steady and quasi-steady maneuver as well as gust loads) are considered and five different mass cases, ranging from empty to maximum take-off mass are used. Steady CFD RANS simulations with free transition modeling are performed for cruise flight conditions to assess the impact of elastic structural deformations caused by different fuel or payload fractions on the performance of the laminar wing. The results reveal that the laminar wing is very robust against elastic structural deformations during cruise flight for the mass cases considered.