Prediction of Helicopter Blade Loads for an Unsteady Pull-Up Maneuver Using Lifting-Line and CFD/CSD Analyses

Abstract

This paper investigates the aeromechanics of a prescribed 2.1g pull-up maneuver for a helicopter rotor. The simulation is carried out using multibody based Computational Structural Dynamics (CSD) model tightly coupled to a high-fidelity Computational Fluid Dynamics (CFD) solver. The predictions are also compared with those obtained using lifting-line based comprehensive analysis to highlight the capabilities of a high-fidelity simulation. The results show considerable improvements in the predicted results by using a CFD model over a traditional lifting-line approach. In particular, coupled CFD/CSD simulation is able to correctly predict the magnitude and phasing of the two dynamic stall cycles on the retreating side of the rotor disk during the maneuver. Further, it shows significant improvement in the predicted peak-to-peak structural loads. The advancing blade stall is not predicted by either of the analysis. The study also shows some deficiencies in the ability to predict blade torsional loads.