Abstract
To simulate the vortex-induced vibration of a circular cylinder, a wake oscillator the length of which flactuated was proposed in this paper. In addition, the effects of the discharged vortices from the wake oscillator were represented by a negative viscous damping of equivalence. The motion of the wake oscillator was expressed by a nonlinear differential equation called "Van der Pol's equation". The equation of motion of the wake oscillator when the cylinder was excited externally, was analized approximately, and examined into the synchronization of frequencies of the lift coefficient and the cylinder motion. The theoretical region of synchronization was compared with some experimental results, and it became clear that the theoretical value agreed fairly with the experimental values. To know the wake behavior on the circular cylinder excited externally over the wide range of wind speed, the nonlinear equation was analized numerically by a digital computer. The numerical results, which were the relation between wind speed and the amplitudes of lift coefficients, the frequencies of cylinder motion and lift coefficients, and the phase shifts of them, proved that the proposed nonlinear wake oscillator would be able to become good model which represented the wake of cylinder vibrated by vortices.
