The evaluation of aerodynamic forces in torsional vibration using unsteady aerodynamic forces under continuous rotational motion

Abstract

Large-amplitude torsional aerodynamic vibrations are perhaps explained by the unsteady aerodynamic forces determined by the angle of attack and the time derivative of it in comparatively higher reduced wind velocity region. In this study, the above-mentioned aerodynamic forces as a function of angle of attack and the time derivative of it were obtained by measuring the aerodynamic forces during continuous rotation at a constant angular velocity on rectangular cylinders with a side ratio of B/D = 2 and 5, where torsional flutter occurs. Using these aerodynamic forces, the unsteady aerodynamic forces during torsional vibrations with various amplitudes in comparatively higher reduced wind velocity region were tried to explain. As a result, the flutter derivatives were expressed for B/D = 2, as well as B/D = 5 shown in the past. Furthermore, the unsteady aerodynamic forces were expressed not only the vibration frequency component which contributes to the work but also higher frequency components.