Vortex induced vibration excitation competition between bare and buoyant segments of flexible cylinders

This paper addresses a practical problem: “Under what fractional coverage of buoyancy modules, would the vortex induced vibration (VIV) excitation on buoyant segments dominate the response?” The source of data is a recent model test on a 38 m long flexible cylinder, densely instrumented with fiber optic strain gauges and accelerometers. A pipe model with five staggered buoyancy configurations was tested. The paper emphasis is on exploring the winner of excitation competition between bare and buoyant segments and offering useful insights on the design of a pipe with staggered buoyancy modules in uniform flow. Four particular topics are covered: (i) the identification of VIV excitation regions, (ii) the experimental determination of the winner of excitation competition between bare and buoyant segments, (iii) the prediction of the winner of excitation competition, and (iv) the factors affecting fatigue damage rate for pipes with staggered buoyancy modules. Potential areas for promising additional research and a general guidance in designing staggered buoyancy pipes are proposed.