Experimental investigation on the suppression of vortex-induced vibration of long flexible riser by multiple control rods

• Published in: Journal of fluids and structures Vol. 30; pp. 115 - 132
• Main Authors: Wu, H., Sun, D.P., Lu, L., Teng, B., Tang, G.Q., Song, J.N.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-04-2012; Elsevier
• Subjects: Computational fluid dynamics; Control rods; Exact sciences and technology; Experiment; Fluid flow; Fundamental areas of phenomenology (including applications); Intervals; Mathematical models; Multiple control rods; Physics; Reynolds number; Risers; Slender riser; Solid mechanics; Structural and continuum mechanics; Vibration, mechanical wave, dynamic stability (aeroelasticity, vibration control...); VIV suppression; Vortex-induced vibration; Vortex-induced vibrations; Multiple control rods; Slender riser; Experiment; VIV suppression; Vortex-induced vibration; Flexible pipe; Vibration; Swirling flow; Reynolds number; Bragg grating; Crossflow; Spacing; Experimental study; Aspect ratio; Modeling; Fiber optic sensors; Vibration control; Riser; Optical fiber
• ISSN: 0889-9746; 1095-8622
• DOI: 10.1016/j.jfluidstructs.2012.02.004

Experimental investigations were conducted to evaluate the vortex-induced vibration (VIV) suppression for slender riser (length to diameter ratio L/D=1750) using multiple control rods. The uniform current was obtained by towing the riser model running in a wave basin, giving the Reynolds numbers ranging from 2400 to 7600. Four control rods with diameter d=0.25D were placed parallel to the riser model with uniform angle interval of 90°. Different spacing ratios δ/D=0.187, 0.375 and 0.562 and coverage rates Lc/L=80%, 60%, 40% and 20% were considered, where δ is the spacing distance, Lc is the covered length. The strain responses in both cross-flow (CF) and in-line (IL) directions were measured by 56 Fiber Bragg Grating sensors. The experimental results show that the multiple control rods perform well in mitigating the VIV. In general the smaller spacing ratio and the larger coverage rates give rise to the better VIV suppression for the CF response, while the IL response is not sensitive to the δ/D and Lc/L. The optimal parameters are suggested to be δ/D≤0.375 and Lc/L≈60%. The monitored end tension of the riser model was observed to increase slightly due to the presence of control rods.