Modellazione aeroelastica e progettazione ottimizzata di rotori di elicottero innovativi a basso livello vibratorio

Abstract

The present research activities is aimed to the development of aeroelastic models of advanced helicopter rotor blades and theirs application to opti- mal design of low-vibration rotors. To this purpose, two di erent solvers, for composite advanced geometry rotor blades, characterized by arbitrary curved/swept elastic axis, have been developed. The rst one is numeri- cally integrated through implementation within the COMSOL Multiphysics Finite-Element-Method (FEM) software code, while the second one is based on a Galerkin spectral approach for numerical integration. The FEM model is based on a nonlinear beam-like formulation already developed in the past for a straight rotor blade, and it has been extended to rotor blades with arbi- trary elastic axis shape, while for the implementation of the Galerkin-based solver having similar capabilities of the FEM-based one, the development of an original curved beam formulation has been necessary. Several numerical results concerning comparisons with numerical and experimental data avail- able in the literature are presented to validate both solvers developed. Then, an optimization procedure for the design of helicopter main rotors that gen- erate low vibratory hub loads in advancing ight is implemented where blade shape and structural properties are the design parameters to be identi ed within a binary genetic optimization algorithm, under aeroelastic stability constraint. The Galerkin-based solver is adopted within the optimization process for the evaluation of the objective function, with the inclusion of a non-conventional, computationally e cient, surrogate wake in ow model for the analysis of sectional aerodynamic loads. Numerical results are pre- sented to demonstrate the capability of the proposed approach to identify low vibratory hub loads rotor blades.