Aerodynamic and Structural Optimisation of Powerplant Integration under the Wing of a Transonic Transport Aircraft

Multi-disciplinary optimisation (MDO) of the outboard engine pylon of a large transonic transport aircraft is reported in this paper. The disciplines involved were structure and aerodynamics, although this paper focuses on the aerodynamic aspect. A two-level strategy was followed to solve this problem: three parameters are identified as playing a coupling role between disciplines and are addressed at a higher level. Remaining parameters are discipline-specific and can be optimized separately at a lower level. For each discipline, a sampling of the high-level design space is realised and each sample is optimised at the lower-level. A Kriging based surrogate model is then built to model lower level behaviour. Finally, gathering the information from the surrogate models of each discipline allows to derive the multi-disciplinary optimum. This approach offers the opportunity to use advanced discipline-specific design methods. This is illustrated in this work by the use of RANS discrete adjoint equations to compute the gradient of the objective function during aerodynamic shape optimisations. Validation work on this state-of-the-art numerical method was carried out and is also presented.