The effect of inclination on vortex-induced vibration of a circular cylinder with a base column

Abstract

The vortex-induced vibration (VIV) of an inclined cylinder can be affected by its end condition. This paper numerically investigates the effect of inclination on the VIV of an elastically mounted rigid cylinder with a base column, which derives from a floating offshore wind turbine (FOWT). The numerical methods are validated against an existing VIV study of a finite-length cylinder. Two inclination angles, i.e. -5° and -10°, are studied to simulate the relatively small wind-induced inclination experienced by FOWTs. Results from stationary simulations show that differences between the force coefficients of inclined and upright cylinders are rather small. Nevertheless, contrary to the finding from previous VIV studies that the effect of inclination on the response of a cylinder with small inclination angles is limited, the present investigation reveals that the maximum response amplitude of the cylinder increases by about 20% when the inclination angle grows to -10° due to the presence of the base column.Meanwhile, the inclination leads to a reduction in the width of the lock-in regime. The impacts of inclination are further discussed via forced vibration studies with same oscillation parameters, which show that the upper part of the cylinder is more affected by the inclination compared to the base column with a considerable decrease in the amplitude of lift coefficient. The discrepancies in fluid forces are substantiated by analysing the pressure distribution on specified spanwise sections of the cylinder surface.

Wave Induced Plume and Hydrodynamic Loads Over Vertical Circular Cylinder Piercing Surface – Numerical Investigation

“…The main factors related to the flow impact were discussed by comparing the generated bow wave height, drag coefficient, pressure coefficient, and velocity vectors at several flow conditions. Previous experimental and numerical studies explored cylinder piercing surface interaction with water which was examined experimentally by Chaplin et al [2] and by using numerical simulation [8], but these studies are limited to low flow velocity. Moreover, the Large Eddy Simulation (LES) approach was used in air-water flow simulation at several Fr but it is limited to Fr 3.5 [11].…”

“…However, LES could accurately predict the generated plume and the flow characteristics, LES requires high computational cost as it solves the large eddies and models the smaller eddies. Furthermore, the forces generated on the stationary cylinder were investigated at low Re [8]. The submersed depth Z of the cylinder in terms of aspect ratio Z/D was found to have a high impact on the produced loads and wake development [9].…”