Book Description

Unconventional aircraft configurations have the potential to reduce aviationâ s contribution to climate change through substantial reductions in fuel burn. One promising configuration which has received much attention is the hybrid wing-body (HWB). Due to the lack of design experience for unconventional configurations, high-fidelity design and optimization methods will be critical in their development. This thesis presents the application of a gradient-based aerodynamic shape optimization algorithm based on the Reynolds-averaged Navier-Stokes equations to the aerodynamic design of conventional tube-and-wing (CTW) and HWB aircraft. The optimal aerodynamic shapes and performance for a range of aircraft sizes including regional, narrow-body, midsize, and wide-body classes are found so as to characterize the aerodynamic efficiency benefits of the HWB configuration with respect to equivalent CTW designs. Trim-constrained drag minimization is performed at cruise, with a large design space of over 400 design variables. The smaller optimized HWBs, including the regional and narrow-body classes, while more aerodynamically efficient, burn at least as much fuel as to the equivalently optimized CTWs due to their increased weight, while the larger wide-body-class HWB has almost 11% lower cruise fuel burn. To investigate alternative configurations which may yield improved efficiency, exploratory optimizations with significant geometric freedom are then performed, resulting in a set of novel shapes with a more slender lifting fuselage and distinct wings. Based on these exploratory results, new lifting-fuselage configurations (LFCs) are designed. The slenderness of the LFC fuselage decreases with aircraft size, such that, for the largest class, the LFC reverts to a classical HWB shape. This new configuration offers higher aerodynamic efficiency than the HWBs, with the smaller classes seeing the largest benefit from the new configuration. This new lifting-fuselage concept offers 6% lower cruise fuel burn than the CTW in the regional class, and a marginal benefit in the narrow-body class. The effects of cruise altitude, stability requirements, and weight sensitivity are also examined.