Buffet Onset Constraint Formulation for Aerodynamic Shape Optimization

High-fidelity computational modeling and optimization of aircraft configurations have the potential to enable engineers to produce more efficient designs with fewer unforeseen modifications late in the design process. For transonic wing design, aerodynamic shape optimization has demonstrated the potential to produce high-performance designs, but these designs are susceptible to buffet. To address this issue, we present a separation-based constraint formulation that can be used to constrain buffet onset in an aerodynamic shape optimization. The developed separation metric is verified against a common buffet prediction method and validated against experimental wind tunnel data. A series of optimizations based on the AIAA Aerodynamic Design Optimization Discussion Group wing-body-tail case are presented to show the need for buffet-onset constraints and to demonstrate the effectiveness of the proposed approach. Both single-point and multipoint optimizations without separation constraints are found to be vulnerable to buffeting, while the optimizations using the proposed approach successfully move the buffet boundary to make the designs feasible.