Guo, Su-XiangSu-XiangGuoSong, Meng-TianMeng-TianSongLei, Jie-ChaoJie-ChaoLeiXu, Hai-LongHai-LongXuCHIEN-CHENG CHANG2025-10-162025-10-162025-08https://www.scopus.com/record/display.uri?eid=2-s2.0-105014322736&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/732687This study employs a force element analysis to investigate vortex-induced vibrations (VIV) of three side-by-side circular cylinders at Reynolds number Re = 100, mass ratio m* = 10, spacing ratios S/D = 3–6, and reduced velocities Ur = 2–14. The lift and drag forces are decomposed into three physical components: volume vorticity force, surface vorticity force, and surface acceleration force. The present work systematically examines varying S/D and Ur effects on vibration amplitudes, frequencies, phase relationships, and transitions between distinct vortex-shedding patterns. By quantitative force decomposition, underlying physical mechanisms governing VIV in the triple-cylinder system are elucidated, including vortex dynamics, inter-cylinder interference, and flow structures. Results indicate that when S/D < 4, cylinders exhibit “multi-frequency” vibration responses. When S/D > 4, the “lock-in” region broadens, and the wake structure approaches the patterns of an isolated single cylinder; in addition, the trajectories of cylinders become more regularized. The forces acting on the central cylinder present characteristics of stochastic synchronization, significantly different from those observed in two-cylinder systems. The results can advance the understanding of complex interactions between hydrodynamic and structural dynamic forces under different geometric parameters that govern VIV response characteristics of marine structures.trueforce element analysislow Reynolds numberside-by-side cylindersVIVjournal article10.3390/jmse130814462-s2.0-105014322736