Application of Low- and High-Fidelity Simulation Tools to Helicopter Rotor Blade Optimization

Abstract

New helicopter rotor designs are desired that offer increased efficiency, reduced vibration, and reduced noise. Multidisciplinary optimization of rotors has been advanced by the development of "comprehensive" rotorcraft analysis tools; however, these tools lack built-in high-fidelity aerodynamic models. Accurate airload predictions utilize computational fluid dynamics (CFD) coupled to the computational structural dynamics (CSD) of a comprehensive code. These methods are too computationally intensive for numerous function calls as in optimization. Thus, an approach is needed where high-fidelity simulations can be routinely used in optimization. The process presented in this paper combines the results of a simplified aerodynamic low-fidelity simulation with a selected number of high-fidelity CFD/CSD simulations. The process is demonstrated for a four-bladed hingeless rotor. Design variables include tip geometry and spanwise twist. Approximation models are built for high-fidelity metrics for rotor efficiency and vibration. Optimization using these approximation models found a design having maximum rotor efficiency while constraining vibration.