Vortex-induced vibration of the variable cross-sectional cylinder cases in transverse direction at Re = 3900 using OpenFOAM

Abstract

The one-degree-of-freedom (1-DOF) vortex-induced vibration in structures with varying cross-sectional shapes and incoming flows have been conducted using numerical simulation. The investigation centers on amplitude, frequency, spectrum, phase and fluid force coefficients. Additionally, the temporal and spatial characteristics as well as vortex dynamics mechanism are scrutinized, particularly during the cross-flow amplitude extremes. It can be indicated through studies that the cross-flow amplitudes in different incoming flows exhibit a distinctive distribution with three discernible branches. Frequency locking is found to amplify the dynamic response of the structure. Four tapered cylinder cases exhibit a delay in the location of the cross-flow amplitude extremes compared to two cylinder cases attributable to the influence of structural shear rate, which expands the upper branch. Superimposing incoming shear rate in the same direction as the structural shear rate not only enhances the cross-flow amplitude extremes but also broadens the range of forces and velocities distribution acting on the structure. Conversely, the imposition of incoming shear rate in the opposite direction to the structural shear rate leads to a contrary outcome. The incoming shear rate introduces secondary frequencies with higher energy in the spectrum characteristics of two cylinder cases, consequently promoting the amplification of the cross-flow amplitudes.