Aeroelastic Modeling of Blade Vibration and its Effect on the Trim and Optimal Performance of Helicopter Rotors using a Harmonic Balance Approach

Abstract

<p>This dissertation concerns the optimization of the aeroelastic performance of conventional</p><p>helicopter rotors, considering various design variables such cyclic and higher</p><p>harmonic controls. A nite element model is introduced to model the structural</p><p>eects of the blade, and a coupled induced velocity/projected force model is used</p><p>to couple this structural model to the aerodynamic model constructed in previous</p><p>works. The system is then optimized using two separate objective functions: minimum</p><p>power and minimum vibrational loading at the hub. The model is validated</p><p>against several theoretical and experimental models, and good agreement is demonstrated</p><p>in each case. Results of the rotor in forward </p><p>ight demonstrate for realistic</p><p>advance ratios the original lifting surface model is sucient for modeling normalized</p><p>induced power. Through use of the dynamics model the vibrational loading minimization</p><p>is shown to be extremely signicant, especially when using more higher</p><p>harmonic control. However, this decrease comes at an extreme cost to performance</p><p>in the form of the normalized induced power nearly doubling. More realistic scenarios</p><p>can be created using multi-objective optimization, where it is shown that vibrational</p><p>loading can be decreased around 60% for a 5% increase in power.</p>