Experimental Study on the Influence of Wave Action on Vortex-Induced Vibration of a Near-Surface Horizontal Submerged Cylinder

• Wave-period resonance amplifies VIV amplitude by 92.9% when matching natural frequency. • Wave-height threshold (H/D≥1.2) switches energy transfer from suppression to enhancement. • Bimodal-to-unimodal transition occurs when vortex frequency approaches wave frequency. • Initial branch maximizes wave-resonance sensitivity; lower branch stabilizes at A*≈0.4. • High waves (H≥0.06m) shift dominance from VIV to wave-induced vibration. Vortex-induced vibration (VIV) energy harvesting represents a promising technology for marine renewable energy exploitation. However, practical application of this technology is constrained by critical hydrodynamic challenges. Specifically, the inherent shear of ocean currents results in a decrease in current velocity with increasing depth, necessitating the placement of energy harvesters near the water surface to maximize energy capture efficiency. Nevertheless, wave action exerts a significant influence on the VIV response of such harvesters. Currently, research regarding the effects of wave modulation on the VIV evolution of near-surface horizontal circular cylinders remains limited, and the influences of key wave parameters on vibration amplitude and frequency characteristics remain largely unexplored. Accordingly, a flume experiment was completed. The vibration responses of a near-surface horizontal circular cylinder were investigated under coupled wave-current interactions. Through spectral analysis, the nonlinear modulation effects of wave period and wave height on the VIV of the cylinder are elucidated, particularly across its three distinct response branches (initial, upper, and lower). The results demonstrate that the relationship between the wave period and the natural period of the cylinder governs the wave-induced influence. A consistent wave period induces a synergistic effect with larger vibration amplitudes than current-only conditions at the same reduced velocity. A divergent wave period triggers a competitive mechanism. Wave height modulates the intensity of the synergy or competition between VIV and wave-induced vibration (WIV).