Single-point and multipoint aerodynamic shape optimization of high-speed civil transport

Single-point and multipoint aerodynamic shape optimization methods were developed and demonstrated for the design of an advanced supersonic transport subject to many geometric constraints. The starting point configuration baseline was developed in support of the NASA High-Speed Research program using linear-theory-based methods and multidisciplinary system analyses. The single-point design method simulated the presence of nacelles and diverters at supersonic cruise by superimposing nacelles-on/nacelles-off pressure differences, from complete configuration analyses, onto single-block-grid wing/body calculations. The multipoint design method used a multiblock grid to treat the complete configuration, including nacelles/diverters, canard, empennage, and wing flaps/slats. Two forms of multipoint optimization were performed at Mach 2.4, 1.1, and 0.9: sequential (design at cruise followed by flap and canard/tail incidence angle optimization at the two transonic conditions) and multipoint (simultaneous design at the three flight conditions via a composite objective function). Euler-based optimization using a combination of the two methods achieved significant performance gains derived from the nonlinear effects. The single-point approach produced much of the improvement, lowering the appropriately weighted thrust coefficient by 4.28 counts after trimming the full configuration at the three design points. (A seven count drag reduction was achieved at cruise for the untrimmed vehicle.) The sequential and multipoint methods achieved 6.03 and 7.55 counts of composite thrust reduction, respectively.