Flow-induced vibration in in-line direction of a circular cylinder in a flow (1st report, measurement of added fluid forces in in-line direction acting on a circular cylinder in a flow)

Precise fluid force measurement by water tunnel test was conducted to investigate the mechanism of flow-induced vibration of a circular cylinder in in-line direction. Added fluid forces acting on a circular cylinder were measured by forced oscillation tests. As a result, it was confirmed that negative damping force acts on a cylinder in a certain range of reduced flow velocity corresponding to the first in-line oscillation region. The measured added damping force was then reduced to exciting parameter, which denotes nondimensional exciting fluid force. The characteristics of exciting parameter and the effect of mass ratio to the stability criteria were discussed in detail.