High-Reynolds-number effects on 2-DOF vortex-induced vibration: A hybrid experimental investigation

This study presents a hybrid experimental investigation of two-degree-of-freedom (2-DOF) vortex-induced vibration (VIV) of a circular cylinder over a Reynolds number range of 5.0 × 1 0 4 – 3.5 × 1 0 5 , nominally covering the TrSL3, TrBL0, and TrBL1 regimes. The framework prescribes structural properties digitally while measuring hydrodynamic forces physically, enabling V r to be varied at a prescribed nominal Re. The results show that Re strongly affects the amplitude, frequency, and coupled-motion characteristics of 2-DOF VIV. In the TrSL3 case, the response retains identifiable initial, upper, and lower branches. As Re increases into TrBL0, the branch-type structure progressively simplifies and the lower branch becomes indistinct. The maximum cross-flow amplitude reaches A y ≈ 2.55 D at Re = 2.0 × 1 0 5 , accompanied by a pronounced in-line response of A x ≈ 0.95 D . The CF amplification associated with CF–IL coupling is evident from TrSL3 to early TrBL0 but weakens at higher Re. The IL-to-CF frequency ratio shifts from f x / f y ≈ 2 at lower Re toward near-unity or subharmonic relations, while trajectories evolve from figure-eight and arc-shaped patterns to butterfly-shaped and irregular motions. These findings demonstrate that high-Re effects modify the coupled response state of 2-DOF VIV, beyond changes in maximum amplitude alone. • Hybrid experiments reveal strong Reynolds-number effects on 2-DOF VIV. • High Reynolds numbers reshape vibration amplitude and response branches. • The peak CF amplitude reaches A y ≈ 2.55 D at Re = 2.0×10 5 . • IL–CF coupling shifts frequency ratios and trajectories at high Re.