High-mode-number vortex-induced-vibration field experiments

This paper presents the initial results from vortex-induced-vibration (VIV) field testing of a long, flexible, model riser at a high mode number. The experiments were designed to gain understanding of the dynamic behavior of a long riser in uniform flow responding at mode numbers ranging from 10 to 25 in crossflow vibration. The observed reduced velocity and root-mean-square (RMS) displacement-response levels were reported. Mean values of the drag coefficient, C d , and hydrodynamic damping derived from measured data were compared with calculated values from formulas commonly used in engineering design of offshore systems.