Effect of traveling waves on Vortex-Induced Vibration of long flexible cylinders

Offshore marine risers and pipelines, exposed to ocean currents, are susceptible to Vortex-Induced Vibration (VIV). Accurate prediction of VIV is necessary for estimating the fatigue life as well as for taking corrective measures to prevent the vibrations. State of the art response prediction methods work reasonably well for short flexible cylinders vibrating at frequencies corresponding to low mode numbers (below the tenth mode). However, for long structures, which respond above the tenth mode, lack of experimental data has until recently impeded progress. Results will be presented from recent field experiments conducted in the Gulf Stream and Lake Seneca, NY. These experiments have provided an opportunity for new insights about the VIV of long flexible cylinders, responding at high mode numbers. The experimental results also include insights on the use of VIV suppression devices such as helical strakes. The experiments reveal that the dominant response of long flexible cylinders is often in the form of traveling waves. High spatial density fiber optic strain gauge measurements are used to obtain estimates of the phase speed of the waves, the response amplitude and the added mass coefficient. The mean added mass coefficient for the bare cylinder is shown to be approximately one and the maximum response amplitude is found to be approximately one diameter. A Green's function, response prediction method, is introduced which is able to emulate both the standing and traveling wave properties observed in the experimental data.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Jaiswal, Vivek, Ph. D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• J. Kim Vandiver.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/49763

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/49763