Investigation of large-amplitude torsional flutter using unsteady aerodynamic forces under continuous rotation

Abstract

Large amplitude aerodynamic vibrations of bluff bodies with three degrees of freedom (DOF), in which horizontal, vertical and torsional directions, are perhaps explained by the unsteady aerodynamic forces determined by the relative angle of attack and the time derivative of it in comparatively higher reduced wind velocity region. For the first step, to verify this idea, these unsteady aerodynamic forces were applied to explain the large-amplitude responses in torsional 1DOF using a rectangular cylinder with a side ratio of five, where the torsional flutter appears. The unsteady aerodynamic forces of the continuously rotating body were measured and tried to define by the relative angles of attack and their time derivatives. These unsteady aerodynamic forces were able to reproduce the unsteady aerodynamic forces under torsional 1DOF forced vibrations. Furthermore, the response amplitudes obtained from the time domain response analyses using these unsteady aerodynamic forces were in good agreement with the results of wind tunnel experiments with the elastically supported body.