This paper describes the initial development of a multibody based comprehensive analysis for the prediction of rotor loads in unsteady manuevering flight. A multibody based finite element structural dynamics model is coupled to an unsteady lifting line aerodynamic model. The aerodynamic model is a N_b bladed transient model which combines 2D airfoil property tables with a Weissinger-L near wake model, a time marching free wake model, and a semi-emperical dynamic stall model (Leishman-Beddoes). First, the structural model is described and validated. Second, the aerodynamic model is described and validated. Idealized maneuvers involving collective ramp inputs, and prescribed deformations for high speed UH-60A flight are used for validation. Third, a reduced order flight dynamics model, using quasi-steady uniform inflow, is developed to calculate rotor control angles in unsteady maneuvers. Finally, the multibody structural dynamics model is tightly coupled to the aerodynamic model to simulate an unsteady UH-60A pull-up maneuver (flight 11029). The control angles are prescribed from the reduced order model. Prediction of control angles appear to be essential for accurate prediction of maneuver loads. General trends in lift and flap bending moment (steady and peak-to-peak) are reasonably predicted. The most significant error stems from the lack of satisfactory prediction of pitching moment stall. This appears primarily due to the uncertainties in the predicted control angles.
展开▼
