An Examination of Blade Load Calculations Based on Rigid-Flexible Coupling Model

Based on the finite rotation hypothesis, a rigid-flexible coupling dynamic model is developed. It introduces three rigid degrees of freedom with respect to classical moderate deflection beam theory. With quasi-steady theory and pre-described wake model, aerodynamic forces are tightly coupled with structural motions. Structural forces and moments are computed while equations of motions are solved. Sectional loads by three load caculation methods are examined by the analysis results of BO105 and the flight test data of the SA349/2 helicopter. Force integration method can handle vast ranges of computation cases. The predictions are relatively good except for the numerical integrating errors. Accuracy of reaction force method depends on the accuracy of response solutions and can not predict the loads at points between nodes. For the articulated rotor, force integration method shows better results than curvature method on retreating side.