Aeroelastic loads of rotor during collective pitch ramp increase in hovering state based on VVPM/GEBT coupling method

To balance the computational accuracy and efficiency of rotor aeroelastic coupling analysis, the Viscous Vortex Particle Method (VVPM) and the Geometrically Exact Beam Theory (GEBT) tight-coupling method are developed. In aerodynamic aspect, the VVPM method and the Leishman-Beddoes (L-B) dynamic stall model which consider the influence of the elastic deformation are used to simulate the wake viscous flow of the rotor and the unsteady aerodynamic characteristics of blades. In structural aspect, the nonlinear dynamic equations which consider the collective pitch ramp increase have been developed based on the GEBT method. The high efficiency and accuracy characteristics of the coupling method are verified by comparative analyses of the steady/unsteady aerodynamic characteristics in the hovering state. Taking the BO105 rotor as a reference, the elastic responses of the blade and its influence on the aerodynamic characteristics are analyzed during collective pitch ramp increase in the hovering state. The results show that the dynamic stall phenomenon tends to occur when the initial collective pitch is large, leading to a rapid increase of the negative moment, a decrease of the section airfoil normal force coefficient, and a weakening of the thrust overshoot. At the end of the collective pitch ramp increase, the elastic blade has a larger range of thrust overshoot area compared to the rigid blade, resulting in a more serious thrust overshoot phenomenon. The delayed shedding of the rotor wake is captured through rotor vortex field simulation, revealing that the induced velocity of rotor disc is responsible for the thrust overshoot phenomenon of the rotor.