Pages 277-278
Fluid force acting on a circular cylinder oscillating in the streamwise direction in a cross flow was measured by forced oscillation test in a water tunnel under the condition of low reduced velocity and small cylinder amplitude. Added mass and added damping coefficients were calculated based on the measured dynamic drag. They reasonably explain the characteristics of the in-line oscillation such as soft oscillator in the 1st excitation region and hysteresis in the 2nd excitation region. The mean drag coefficient and dynamic lift coefficient attain to their maximum at the reduced velocity between the 1st and 2nd excitation region where the added damping coefficient has its local maximum. It suggests that the increase of the mean drag coefficient induced by the formation of alternate vortices magnifies fluid damping effect and it contributes to the damping region between the 1st and 2nd excitation region.
