A Robust and High-Fidelity Aerodynamic Optimization Design of Truss-Braced-Wing Aircraft with Gradient-Based Method

With a large span and high aspect ratio wing, as well as a lower sweep and thin thickness, the truss-braced-wing (TBW) aircraft is one of the most promising innovative designs for the next generation airliner in both economic and environmental perspectives. Nevertheless, it is still a crucial challenge to conduct the comprehensive robust refined aerodynamic design of full TBW wing-body-tail configuration. Especially, the complex mutual interference among the wing, struts, and fuselage should be seriously analyzed. Meanwhile, for its one typical cruise condition with Ma=0.70 and C_L=0.77, which is unusual compared to the conventional transonic tube-and-wing single-aisle aircraft with nearby Ma=0.78 and C_L=0.5, the aerodynamic explorations and performances of drag divergence and near buffet-onset condition are also fateful and indispensable design aspects. To deal with these issues, we perform three aerodynamic optimization designs by adopting high-fidelity Reynolds-averaged Navier–Stokes solver and gradient-based optimizer in this study. These designs include a single-point optimization, a 2-point optimization and, a 3-point optimization with 600 shape variables and 8 twist variables in a structured mesh. Results indicate that the single-point design obtains a nearly shock-free optimized configuration with an elliptical-close wing load distribution and a lift-to-drag ratio of 24.09. Also, the refined local aerodynamic analyses lead to a good understanding of the complicated interactions with several junctions. In terms of multipoint optimizations, both multipoint optimized configurations have the same level aerodynamic behavior on cruise condition compared with the single-point result, and have a satisfying performance of drag divergence. Moreover, the 3-point optimization has an excellent aerodynamic efficiency with some extra off-design points evaluations, while the 2-point optimization still has an undesirable off-design result.