Two-degree-of-freedom vortex-induced vibrations of a circular cylinder in the vicinity of a stationary wall

Abstract

This paper presents a numerical investigation on the two-degree-of-freedom vortex-induced vibrations of a single circular cylinder near a stationary plane for gap ratio G/D = 0.6 – 3.0, normalized boundary layer thickness δ∕D=0 – 3.5, Reynolds number Re=100 and reduced velocity Ur=2 – 16, where D is the cylinder diameter. Extensive simulations are carried out to capture the features of the cylinder vibration, hydrodynamic forces, and wake flows. Three regimes are classified based on the characteristics of the vibration responses at different boundary layer thicknesses, with the largest vibration amplitude in both the streamwise and transverse directions achieved in regime II. Hysteresis exists between the initial and lower branches due to the bi-stability of the boundary layer reattachment point on the vibrating cylinder. The phase difference between the vortex lift and the displacement shows a 180°jump at the initial → lower branch transition. Within the transition, the total lift is dominated by the second harmonic.