Dynamic mechanism of phase differences in One？degree

The purpose of this study is to provide some insights into the phase mechanism of a cylindrical vortex–induced vibration. A transient coupled fluid–structure interaction numerical model is adopted to simulate a cylindrical vortex–induced vibration. The vortex shedding around the cylinder is investigated numerically by a two-dimensional large eddy simulation approach which can catch more details of the flow field and more accuracy on computing hydrodynamic forces. The vortex shedding modes and response and hydrodynamic forces of a cylindrical vortex–induced vibration are acquired with varied frequency ratios. According to differences in the vortex shedding location, the vortex wake can be characterized by two kinds of mode, the “first mode” and the “second mode.” The mechanisms behind the phases of the first mode and the second mode vortex wakes are investigated, and it is found that the flow speed induced by a cylindrical transverse vibration and the position of a vortex release are the root causes of the phase difference between the lift coefficient and transverse displacement. The speeds caused by a cylinder vibration and a cylinder-shed vortex are the reasons that the lift amplitude of an oscillatory cylinder is different from that of a fixed cylinder