Helicopter Rotor Design using Adjoint-based Optimization in a Coupled CFD-CSD Framework

A formulation for sensitivity analysis of the fully coupled time-dependent aeroelastic analysis of helicopter rotors is given in this paper. Both forward sensitivity and adjoint sensitivity formulations are derived that correspond to analogues of the non-linear aeroelastic analysis problem. Both sensitivity analysis formulations make use of the same iterative disciplinary solution techniques used for analysis, and make use of an analogous coupling strategy. The information passed between fluid and structural solvers is dimensionally equivalent in all cases, enabling the use of the same data structures for analysis, forward and adjoint problems. Sensitivities for the fully coupled aeroelastic problem are verified using the complex step method and agreement to machine precision is demonstrated. Future work will involve using these sensitivities in the context of a coupled aeroelastic rotor optimization problem.