Effects of bed-proximity on VIV onset of an elastically mounted circular cylinder with low to high mass-damping parameters

• Combined effects of bed-proximity and mass-damping on VIV onset of an elastically mounted cylinder were physically investigated. • A low structural-damping VIV device was developed, and an innovative upward-illumination PIV system was employed. • Under low-( m *+ C A ) ζ conditions, Vr cr decreases exponentially as e/D decreases below 1.0. Under high-( m *+ C A ) ζ conditions, Vr cr exhibits opposite trend with decreasing e/D . • Empirical relationships between Vr cr and e/D were established for various values of mass-damping parameter. Vortex-induced vibrations (VIVs) of cylindrical structures present significant challenges in engineering practices. While most existing studies have focused on wall-free scenarios. This work experimentally investigates the combined effects of bed-proximity and mass-damping on the onset of transverse VIVs of an elastically mounted cylinder subjected to turbulent shear flow in a recirculating water flume. The mass-damping parameter K s was varied from low to high values, with the gap ratio e/D ranging from 2.0 to 0.20. Flow field measurements were conducted using an innovative upward-illumination PIV, structural vibration and associated wake fluctuation were captured concurrently. Experimental findings demonstrate that the critical reduced velocity ( Vr cr ) for onset of VIV remains highly consistent at e / D > 1.0 under constant K s , and increases as K s increased for a fixed value of e/D . Under low- K s conditions, Vr cr decreases exponentially as e/D falls below 1.0. Conversely, the opposite trend is observed under high- K s conditions. These contrasting behaviors may be attributed to the competition among multiple factors: in the former case, stronger disturbances to the cylinder and an increasing Strouhal number facilitate the onset of near-bed VIV; in the latter, however, reduced vortex-shedding strength and enhanced energy dissipation capacity suppress the onset of near-bed VIV. Empirical correlations between Vr cr and e/D were established for various values of K s . A correction factor ψ is proposed to quantitatively characterize the combined bed-proximity and mass-damping effects on Vr cr . The present study thus provides a valuable supplement to the DNV GL guidelines for predicting the onset of VIVs in submarine pipelines near the seabed.