Calculation of Rotor Responses with Abrupt Increase of Collective Pitch Based on Time-Accurate Free-Wake Method

Aerodynamic characteristics and responses of rotor with control inputs present complex unsteadiness.A time-accurate free-wake calculation method was developed based upon wake model,PC2B algorithm,blade model,unsteady airfoil model and trim model.Using the developed method,the calculations on rotor inflow for forward flight and thrust coefficient with ramp increase in rotor collective pitch angle for hover were firstly carried out.By comparisons between the calculated results and available experimental data,the capability of the present method was demonstrated.Then,the rotor thrust coefficient,moment coefficient and blade flapping responses with the abrupt increase of collective pitch angle were calculated and analyzed,and some meaningful results were obtained.