Research on the Coupled Bending–Torsional Flutter Mechanism for Ideal Plate

In order to explore the inducing mechanism of negative damping of bending–torsional coupling flutter, an ideal plate with a width of 0.45 m was taken as the research object. The changes in frequency, critical wind speed, aerodynamic stiffness, and aerodynamic damping were systematically analyzed by using the “incentive-feedback” mechanism theory. The source of modal damping and the inducing mechanism of bending–torsional coupling flutter were identified. The research results show that the torsional modal damping of the ideal plate mainly comes from the aerodynamic positive damping of the torsional velocity self-excitation (A2*) and the aerodynamic negative damping of the torsional displacement incentive feedback (A1*H3*). Among them, the aerodynamic negative damping of the item (A1*H3*) causes the torsional mode damping to be negative, and the ideal plate undergoes bending–torsion-coupled flutter under the drive of the torsional mode aerodynamic negative damping. The reason why the aerodynamic damping of the item (A1*H3*) is negative depends on two aspects: one is that the flutter derivatives A1* and H3* have opposite signs; the second is that the torsional displacement self-excited lift excites the vertical vibration to produce negative stiffness −mhωsα2. This results in the phase difference between the torsional displacement self-excited lift and the vertical displacement response in the range of (90–180°).