AEROELASTIC ANALYSIS FOR HELICOPTER ROTOR BLADES IN HOVER AND FORWARD FLIGHT

摘要

Aeroelastic characteristics considering wake effects for helicopter ro tor blades in hover and forward flight were inv estigated. To take in to account the large deformations of rotor blades, a large deflection beam model was used. Also, to estimate unsteady wakes and calculate its induced velocities, a freewake model w as applied. The aerodynamic forces of the rotor blades were obtained by using a vortex lattice method (VLM) in hover and forward fligh t. In the case of the hovering flight, Newton-Raphson iterative method was applie d to the aeroelastic analysis to obtain the numerical solutions for steady-state blade deflections. The flap, lag, and torsion deflections considering wake effects by using the freewake model were investigated. The p-k method in the frequency domain was used to predict the lag damping and frequency, which are directly relevant to the dynamic stability of helicopter rotor blades. The numerical results were compared to the experiments and the ones using a tw o-dimensional quasi-steady model with a un iform inflow model. For thefo rward flight, nonlinear periodic blade responses were obtained by integrating the full fin ite element equation in time through a coupled procedure with a vehicle tr im. After th e periodic blad e deflections were obtained, the stability analysis was performed for the linear lized stability equations with a Floquet transition matrix. The numerical results using the fre ewake model were compared to the ones using the two-dimensional quasi-steady model.