Effects of oscillation amplitude on aerodynamic derivatives

In this paper, the effects of oscillation amplitude on the aerodynamic derivatives of the thin rectangular cylinder with B/D=13 and 150 were investigated. It was clear that the torsional amplitude affected strongly the aerodynamic derivatives H2* and A2*. This effect reduced the critical velocity of flutter by about 10%. The cause of this effect was investigated by the measurement of the unsteady surface pressure. This investigation made it clear that the variation of A2* is caused by the movement of the acting point of the resultant lift force. These results indicate that these effects cannot be disregarded for such a simple thin plate but for a real bridge girder with a more complex cross-section and with delicate aerodynamic control devices.