VIV response of a long flexible riser fitted with different helical strake coverages in uniform and linearly sheared currents

Abstract

ABSTRACTAn experimental investigation was conducted on a flexible riser with and without various helical strake coverages, with the aim of further improving the understanding of the response performance of the vortex-induced vibration (VIV) of a riser with helical strakes. Two current profiles, including uniform and linearly sheared currents, were simulated. The VIV displacements, VIV strains and hydrodynamic forces were directly measured from the test. Based on the fatigue damage method, the fatigue damage was obtained from the measured strain. Strakes with different coverages were analysed, and response parameters such as the displacement response and fatigue damage were studied. The results of the straked model test indicate that the response characteristics of a bare riser model can be quite distinct from those of a riser with helical strakes, and the response performance closely depends on the coverage of the helical strakes. The results also show that the flexible riser with 75% and 50% strake coverages are the best configurations to suppress VIV fatigue damage in uniform and linearly sheared currents, respectively.