Aerodynamic Shape Optimization of a Blended-Wing-Body Regional Transport for a Short Range Mission

The blended-wing-body represents a potential revolution in efficient aircraft design. A lift-constrained drag-minimization optimization problem is solved for the optimal shape of a blended-wing-body transonic regional jet. A Newton-Krylov solver for the Euler and Reynolds-Averaged Navier-Stokes (RANS) equations is coupled with a gradient-based optimizer, where gradients are calculated via the discrete adjoint method. A 98-passenger regional jet is optimized for a 500nmi mission at 40,000ft and Mach 0.8. A series of single and multipoint optimization problems using both the Euler and RANS equations are considered in order to examine the trade-offs between the imposition of different constraints including trim and longitudinal static stability. Drag reductions of up to 55% and 38% are achieved for the Euler and RANS-based optimizations respectively. In each case an elliptical lift distribution is attained on the wing, shocks are eliminated, and in the RANSbased optimization the large regions of highly separated flow on the baseline design are greatly reduced. These drag reductions are achieved while both trimming and stabilizing the baseline design.