A geometric sensitivity study for the aerodynamics of a strut-braced airframe

A global sensitivity analysis method, the adaptive-cut high-dimensional model representation method (HDMR) is considered to evaluate the impact of geometrical changes of a ultra-high aspect ratio strut-braced wing configuration on the aerodynamic performance. A data-driven reduced order model based on Proper Orthogonal Decomposition is used to keep the computational cost of the analysis at a manageable level. The airframe configuration is described using 7 geometrical parameters, which comprise the design space. The geometrical parameters are decomposed and analysed across their whole range of values by the HDMR to assess their influence on the Drag coefficient, Lift coefficient and Lift-to-Drag ratio of the aircraft. These results form the basis for a qualitative exploration of the aerodynamics of such airframes further augmented by high-fidelity CFD simulations. Results show that the sweep angle of the wing is the dominant parameter in terms of Drag due to changes in shock wave intensity. Changes in the wing root chord also implicitly affect the local geometry at the wing-strut junction, which influences the blockage effect and thus the intensity of the shock waves at the junction. Lift is affected primarily by the twist of the wing. Overall, the strut is shown to have significant effects on the performance of the aircraft design due to the presence of strong shock waves at the wing-strut junction and interference effects.