Numerical Study of New Device for Passive Suppression of Vortex-Induced Vibrations in Deep Water Risers

Abstract

This paper presents a three dimensional numerical simulation to investigate the effectiveness of a new passive device for vortex-induced vibrations (VIV) suppression of deep water risers based on non-continuous helical strakes in staggered arrangement with two starts. The influence of changing the geometries and design parameters, such as the pitch and shape of strakes, on the VIV was studied. The simulation had been carried out at Reynolds number 104, which satisfies the natural conditions of ocean currents. The presented design has been tested using a numerical solver using OpenFOAM platform, which had been presented and validated using number of published benchmarks. The LES – large-eddy simulation is used for turbulence modeling. The results had been compared with the published numerical and experimental works and other design based on drag coefficient. The comparison shows that the proposed geometry can suppress the VIV, if applied in deep water risers. The drag coefficient of 1.05 is considered a reduced value in the modified strakes shape with two starts and non-continuous helical strakes in staggered arrangement. The addition of strakes to the surface of a flexible cantilever was modeled to give the chance for evaluating the effect of geometry on the VIV.