摘要
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.
