Large amplitude aerodynamic vibration of rectangular cylinder with a side ratio of two

First International Symposium on Flutter and its Application (May 15-17, 2016. Mielparque-tokyo), Minato-ku, Tokyo, Japan

In general, flutter instabilities of bluff bodies are investigated in the very small amplitude region. The main interests of engineers are to know whether the instabilities appear or not, and to evaluate their onset wind velocities. Therefore, the behaviors of self-induced vibrations at the large amplitude region still remain unexplained. It can be supposed that the amplitudes of so-called divergent type vibrations do not continue increasing all the time, even the structures allow to vibrate. Then, in this study, a rectangular cylinder with a side ratio of two is used to investigate its large amplitude vibrations under three DOF condition with various angles of attack. It is well known that this cylinder shows single DOF flutters, such as the galloping and the torsional flutter at the angle of attack 0 degree. Then, the appearance of aerodynamic interferences between these vibrations is expected in three DOF condition. However, to avoid the interference with Karman vortices, the wind tunnel tests were conducted at comparatively high reduced wind velocity region. To obtain the large amplitudes in the wind tunnel, the model was mounted by an elastic support system, which is used for the models of overhead transmission lines. Then, the various kinds of self-induced vibration with large amplitudes were observed, e.g. vertical 1DOF dominant vibration, torsional 1DOF dominant vibration, coupled 3DOF vibration and so on. It depends on the angle of attack and the initial condition which phenomenon occurs. To understand these complicated responses, the time history analyses using quasi-steady aerodynamic forces are tried. Also, the aerodynamic force, which has in-phase component to torsional velocity, is added to the quasi-steady formulation virtually. Then, the most of large amplitude vibrations can be explained by using the quasi-steady aerodynamic forces and/or the aerodynamic force attributable to torsional velocity.

形態: カラー図版あり

Physical characteristics: Original contains color illustrations

資料番号: AA1630046064

レポート番号: JAXA-SP-16-008E