RANS-based Aerodynamic Shape Optimization of a Blended-Wing-Body Aircraft

A series of RANS-based aerodynamic shape optimization for an 800-passenger blended-wing-body aircraft is performed. A gradient-based optimization algorithm and a parallel structured multiblock RANS solver with Spalart–Allmaras turbulence model are used. The derivatives are computed using a discrete adjoint method considering both frozen-turbulence and full-turbulence assumptions. A total of 274 shape and planform design variables are considered. The objective function is the drag coefficient at nominal cruise condition. Lift, trim and root bending moment are constrained. Control surfaces at the rear centerbody are used to trim the aircraft via a nested free-form deformation volume approach. The optimized design is trimmed and stable in both onand off-design conditions. The drag coefficient of the optimized design is reduced by 37 counts with trim and bending moment constraints satisfied. The addition of planform design variables provide an additional 2 drag count reduction.