ROTOR LOADS VALIDATION UTILIZING A COUPLED AEROELASTIC ANALYSIS WITH REFINED AERODYNAMIC MODELING

The effects of refined aerodynamic modeling on rotor blade section loads and bending moments are investigated. A non-linear aerodynamic analysis, for attached flow, separated flow, and dynamic stall, is incorporated into a coupled rotor aeroelastic analysis. Both prescribed and free wake models are also coupled into the analysis. Blade responses and loads are calculated using a finite element formulation in space and time. A modified Newton iterative method is used to calculate blade response and trim controls as one coupled solution. A correlation with SA349/2 Aerospatiale Gazelle flight test data is used to validate the analysis. Trim controls, blade section aerodynamic loads, and blade flap bending moments are satisfactorily predicted. The non-linear aerodynamic model improves correlations in a high speed, high thrust, flight condition. Blade loads, at this flight condition, are quite sensitive to the vehicle trim state. Compressibility significantly affects the amount of flow separation on the rotor. The free wake analysis is important for capturing the harmonics of flap bending moments and low speed aerodynamic loadings.