Vortex-Induced Vibrations Of A Flexible Cylinder Near A Plane Boundary In Steady Flow

Abstract

Vortex-Induced Vibrations Of A Flexible Cylinder Near A Plane Boundary In Steady Flow D.T. Tsahalis; D.T. Tsahalis Shell Development Co. Search for other works by this author on: This Site Google Scholar Warren T. Jones Warren T. Jones Shell Development Co. Search for other works by this author on: This Site Google Scholar Paper presented at the Offshore Technology Conference, Houston, Texas, May 1981. Paper Number: OTC-3991-MS https://doi.org/10.4043/3991-MS Published: May 04 1981 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Tsahalis, D.T., and Warren T. Jones. "Vortex-Induced Vibrations Of A Flexible Cylinder Near A Plane Boundary In Steady Flow." Paper presented at the Offshore Technology Conference, Houston, Texas, May 1981. doi: https://doi.org/10.4043/3991-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsOffshore Technology ConferenceOTC Offshore Technology Conference Search Advanced Search ABSTRACTModel tests were carried out in a current tank to determine the effect of the proximity of a plane boundary on the vortex-induced vibrations of a flexible pipe. The response of the center of the pipe span was measured using an optical tracking system. It was found that in the presence of a plane boundary, the maximum amplitude of vibration is limited, and the onset of vortex-induced vibrations of appreciable amplitude occurs at higher velocities than when no boundary is present.INTRODUCTIONA steady flow about a bluff body, such as a pipeline with a circular cross section, will separate from the body and form a wake. Because of the instability and mutual interaction of the separated shear layers, vortices form and periodically shed from alternate sides of the body. This periodicity in the flow field leads to time dependent pressures distributed over the surface of the body. The result is steady and unsteady drag forces in line with the flow and unsteady lift forces in the transverse, or cross-flow direction. If the pipeline is flexible and/or flexibly supported, it begins to vibrate under the action of these periodic forces. The vibrations of the pipeline modify the flow and lead to a nonlinear interaction between the elastic and the fluid systems. The maximum amplitude of in-line vortex-induced vibrations is much smaller than the maximum amplitude of transverse vortex-induced vibrations, so their contribution to the fatigue life of a structure is small. Consequently, the inline vibrations are not addressed in this study, and attention is focused on the transverse vibrations which will be referred to as "vortex-induced vibrations" hereafter. In the last ten years a number of comprehensive overviews of this important class of fluid-structure interaction problems have appeared [1-5].Experience with unburied offshore pipelines laid in strong current areas has shown that such pipelines may develop unsupported spans due to seabottom being scoured out from under the pipeline due to current action. In turn such unsupported spans exposed to currents may undergo vortex-induced vibrations which may affect the fatigue life of the pipeline. Consequently, the knowledge of the amplitude and frequency response of a pipe in close proximity to a plane boundary (seabottom) and undergoing vortex-induced vibrations is needed in determining its fatigue life.Unfortunately, almost all published theoretical, numerical, and experimental studies on the vortex-induced vibrations of bluff bodies, and specifically pipelines, deal with either isolated pipes or bundles of pipes. The only studies that address the problem of vortex-induced vibrations of a pipe in close proximity to a boundary (wall) are the experimental studies by Wilson and Caldwell [6] and King and Jones [7].Wilson and Caldwell performed experiments in a water tank by towing cylindrical models (pipes) of smooth, hard rubber mounted horizontally next to the flat bottom of the tank. They determined the lowest free-stream velocity (critical velocity) at which the models began to vibrate significantly due to vortex-shedding for gap ratios (pipe-to-wall gap divided by pipe diameter) of 0.25 to 6.8. Keywords: proximity, boundary, pipeline, pipe, pipe-to-wall gap, vortex-induced vibration, frequency, cylinder, vibration, amplitude Subjects: Pipelines, Flowlines and Risers This content is only available via PDF. 1981. Offshore Technology Conference You can access this article if you purchase or spend a download.