Vortex-induced vibration of elastically connected multiple circular cylinders in a side-by-side arrangement in steady flow

Abstract

Vortex-induced vibration (VIV) of multiple circular cylinders elastically connected together in a side-by-side arrangement subject to steady flow is investigated numerically at a low Reynolds number of 150 and a mass ratio of 2. Simulations are conducted for two-, five- and ten-cylinder systems over a wide range of reduced velocities. The aim of the study is to identify the high-amplitude response range of the reduced velocity for the multiple degree of freedom vibration system and identify the difference between the responses of the single- and multiple-degree-of-freedom vibrations. Unlike the single cylinder case, distinct lock-in between the response frequency and any of the structural natural frequencies in a wide range of reduced velocity is not observed in the multiple-cylinder cases. Instead, the response frequency increases continuously with increasing reduced velocity. High response amplitudes are found when the response frequency is between the first and the highest modal frequencies. In a multiple-cylinder system, the single-mode response, where the vibration is dominated by one mode, can be only found in low reduced velocity range. In the single-mode branch, the dominance of a single mode shape in the response can be clearly identified except at the boundary reduced velocity between two modes. The maximum response amplitude occurs in the multiple-mode response and interaction between the vortices in the wake of the cylinders is strong when the response amplitudes are high.