High-Fidelity Optimization Framework for Helicopter Rotors

An optimization framework for helicopter rotors based on high-fidelity coupled CFD/CSM analyses is presented. For this purpose the optimization software DAKOTA has been linked to a parametric geometry unit, a mesh generation unit and a fluid-structure module which consists of the DLR flow solver FLOWer coupled with the Comprehensive Rotorcraft Code HOST from Eurocopter. The optimization framework is first applied to various optimization problems in hover starting with the easy task of optimizing the twist rate for the 7A model rotor. The complexity of the optimizations is increased step by step and finishes with an optimization case involving all seven design parameters showing its superiority over simpler optimization problems with respect to the achieved improvement. In the next step the framework is operated in forward flight condition also for the optimization of the twist rate. Small improvements with respect to the 7A rotor are made though indicating the conflicting nature of hover and forward flight requirements. Thus a multi-objective optimization for the twist of the 7A rotor is carried out.