Vortex-induced vibrations of a long flexible cylinder in shear flow
We investigate the in-line and cross-flow vortex-induced vibrations of a long cylindrical tensioned beam, with length to diameter ratio L/D = 200, placed within a linearly sheared oncoming flow, using three-dimensional direct numerical simulation. The study is conducted at three Reynolds numbers, fr...
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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Cambridge University Press
2013
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| Online Access: | http://hdl.handle.net/1721.1/79692 https://orcid.org/0000-0002-4566-5693 https://orcid.org/0000-0002-4960-7060 |
| _version_ | 1811071206585008128 |
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| author | Triantafyllou, Michael S. Bourguet, Remi Karniadakis, George E. |
| author2 | Massachusetts Institute of Technology. Department of Mechanical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Mechanical Engineering Triantafyllou, Michael S. Bourguet, Remi Karniadakis, George E. |
| author_sort | Triantafyllou, Michael S. |
| collection | MIT |
| description | We investigate the in-line and cross-flow vortex-induced vibrations of a long cylindrical tensioned beam, with length to diameter ratio L/D = 200, placed within a linearly sheared oncoming flow, using three-dimensional direct numerical simulation. The study is conducted at three Reynolds numbers, from 110 to 1100 based on maximum velocity, so as to include the transition to turbulence in the wake. The selected tension and bending stiffness lead to high-wavenumber vibrations, similar to those encountered in long ocean structures. The resulting vortex-induced vibrations consist of a mixture of standing and travelling wave patterns in both the in-line and cross-flow directions; the travelling wave component is preferentially oriented from high to low velocity regions. The in-line and cross-flow vibrations have a frequency ratio approximately equal to 2. Lock-in, the phenomenon of self-excited vibrations accompanied by synchronization between the vortex shedding and cross-flow vibration frequencies, occurs in the high-velocity region, extending across 30% or more of the beam length. The occurrence of lock-in disrupts the spanwise regularity of the cellular patterns observed in the wake of stationary cylinders in shear flow. The wake exhibits an oblique vortex shedding pattern, inclined in the direction of the travelling wave component of the cylinder vibrations. Vortex splittings occur between spanwise cells of constant vortex shedding frequency. The flow excites the cylinder under the lock-in condition with a preferential in-line versus cross-flow motion phase difference corresponding to counter-clockwise, figure-eight orbits; but it damps cylinder vibrations in the non-lock-in region. Both mono-frequency and multi-frequency responses may be excited. In the case of multi-frequency response and within the lock-in region, the wake can lock in to different frequencies at various spanwise locations; however, lock-in is a locally mono-frequency event, and hence the flow supplies energy to the structure mainly at the local lock-in frequency. |
| first_indexed | 2024-09-23T08:47:36Z |
| format | Article |
| id | mit-1721.1/79692 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T08:47:36Z |
| publishDate | 2013 |
| publisher | Cambridge University Press |
| record_format | dspace |
| spelling | mit-1721.1/796922022-09-30T11:16:28Z Vortex-induced vibrations of a long flexible cylinder in shear flow Triantafyllou, Michael S. Bourguet, Remi Karniadakis, George E. Massachusetts Institute of Technology. Department of Mechanical Engineering Bourguet, Remi Triantafyllou, Michael S. We investigate the in-line and cross-flow vortex-induced vibrations of a long cylindrical tensioned beam, with length to diameter ratio L/D = 200, placed within a linearly sheared oncoming flow, using three-dimensional direct numerical simulation. The study is conducted at three Reynolds numbers, from 110 to 1100 based on maximum velocity, so as to include the transition to turbulence in the wake. The selected tension and bending stiffness lead to high-wavenumber vibrations, similar to those encountered in long ocean structures. The resulting vortex-induced vibrations consist of a mixture of standing and travelling wave patterns in both the in-line and cross-flow directions; the travelling wave component is preferentially oriented from high to low velocity regions. The in-line and cross-flow vibrations have a frequency ratio approximately equal to 2. Lock-in, the phenomenon of self-excited vibrations accompanied by synchronization between the vortex shedding and cross-flow vibration frequencies, occurs in the high-velocity region, extending across 30% or more of the beam length. The occurrence of lock-in disrupts the spanwise regularity of the cellular patterns observed in the wake of stationary cylinders in shear flow. The wake exhibits an oblique vortex shedding pattern, inclined in the direction of the travelling wave component of the cylinder vibrations. Vortex splittings occur between spanwise cells of constant vortex shedding frequency. The flow excites the cylinder under the lock-in condition with a preferential in-line versus cross-flow motion phase difference corresponding to counter-clockwise, figure-eight orbits; but it damps cylinder vibrations in the non-lock-in region. Both mono-frequency and multi-frequency responses may be excited. In the case of multi-frequency response and within the lock-in region, the wake can lock in to different frequencies at various spanwise locations; however, lock-in is a locally mono-frequency event, and hence the flow supplies energy to the structure mainly at the local lock-in frequency. United States. Office of Naval Research (Grant N00014-07-1-0135) United States. Office of Naval Research (Grant N00014-07-1-0446) BP (Firm) (MIT Major Projects Research Program) 2013-07-24T18:11:48Z 2013-07-24T18:11:48Z 2011-04 2010-12 Article http://purl.org/eprint/type/JournalArticle 0022-1120 1469-7645 http://hdl.handle.net/1721.1/79692 Bourguet, Remi, George E. Karniadakis, and Michael S. Triantafyllou. Vortex-induced Vibrations of a Long Flexible Cylinder in Shear Flow. Journal of Fluid Mechanics 677 (June 27, 2011): 342-382. © Cambridge University Press 2011 https://orcid.org/0000-0002-4566-5693 https://orcid.org/0000-0002-4960-7060 en_US http://dx.doi.org/10.1017/jfm.2011.90 Journal of Fluid Mechanics Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf Cambridge University Press MIT web domain |
| spellingShingle | Triantafyllou, Michael S. Bourguet, Remi Karniadakis, George E. Vortex-induced vibrations of a long flexible cylinder in shear flow |
| title | Vortex-induced vibrations of a long flexible cylinder in shear flow |
| title_full | Vortex-induced vibrations of a long flexible cylinder in shear flow |
| title_fullStr | Vortex-induced vibrations of a long flexible cylinder in shear flow |
| title_full_unstemmed | Vortex-induced vibrations of a long flexible cylinder in shear flow |
| title_short | Vortex-induced vibrations of a long flexible cylinder in shear flow |
| title_sort | vortex induced vibrations of a long flexible cylinder in shear flow |
| url | http://hdl.handle.net/1721.1/79692 https://orcid.org/0000-0002-4566-5693 https://orcid.org/0000-0002-4960-7060 |
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