Time-Dependent Aeroelastic Adjoint-Based Aerodynamic Shape Optimization of Helicopter Rotors in Forward Flight

Abstract

A formulation for sensitivity analysis of fully coupled time-dependent aeroelastic rotors in forward flight with trim constraints is given in this paper. The formulation includes the effect of blade shape parameters as well as blade cyclic pitch control parameters to enable analysis and optimization of rotors in a trimmed condition. Both forward sensitivity and adjoint sensitivity formulations are derived that correspond to analogs of the nonlinear aeroelastic analysis problem. Both sensitivity analysis formulations make use of the same iterative disciplinary solution techniques used for analysis, and they make use of an analogous coupling strategy. The fully coupled aeroelastic analysis formulation is first verified to effectively perform performance predictions of a four-bladed rotor in forward flight started impulsively from rest. Upon successful verification of the fully coupled adjoint formulation, it is used to perform trim and aerodynamic shape design optimization for helicopter rotors in forward-flight conditions.