Vortex-Induced Vibration of Horizontal Circular Cylinder in Uniform Flow

This paper treats Vortex-Induced Vibration (VIV) of a cylinder in uniform flow. The cylinder is aluminum, rigid, circular, and 0.490 m in length, 0.025 m in diameter, and its weight is counterbalanced by buoyancy. The cylinder is horizontally mounted in a two-dimensional tank and allowed to move vertically by hanging through a spring during towing. The equation of motion of the structure is described in the nonlinear form and an approximate solution of the equation is obtained by using a vibrational theory. Lock-in phenomena appear when the vortex shedding frequency approaches to the natural frequency of the structure. Experimental results show that the oscillation of structure has remarkable two frequencies corresponding to the shedding frequency and the natural frequency of the structure. By using amplitude of vertical displacement at the top peak frequency, this paper proposes a way of estimating the transverse force, i.e., lift coefficient during VIV. The estimated lift coefficients are similar to the measured lift coefficients with the vertical displacement restricted to be zero. The estimated lift coefficients seem to be feasible.