U-shaped fairings suppress vortex-induced vibrations for cylinders in cross-flow
We employ three-dimensional direct and large-eddy numerical simulations of the vibrations and flow past cylinders fitted with free-to-rotate U-shaped fairings placed in a cross-flow at Reynolds number 100 ⩽ Re ⩽ 10,000. Such fairings are nearly neutrally buoyant devices fitted along the axis of long...
| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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Cambridge University Press
2017
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| Online Access: | http://hdl.handle.net/1721.1/110825 https://orcid.org/0000-0002-4960-7060 |
| _version_ | 1811076888740757504 |
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| author | Yu, Yue Constantinides, Yiannis Karniadakis, George Em Xie, Fangfang Triantafyllou, Michael S |
| author2 | Massachusetts Institute of Technology. Department of Mechanical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Mechanical Engineering Yu, Yue Constantinides, Yiannis Karniadakis, George Em Xie, Fangfang Triantafyllou, Michael S |
| author_sort | Yu, Yue |
| collection | MIT |
| description | We employ three-dimensional direct and large-eddy numerical simulations of the vibrations and flow past cylinders fitted with free-to-rotate U-shaped fairings placed in a cross-flow at Reynolds number 100 ⩽ Re ⩽ 10,000. Such fairings are nearly neutrally buoyant devices fitted along the axis of long circular risers to suppress vortex-induced vibrations (VIVs). We consider three different geometric configurations: a homogeneous fairing, and two configurations (denoted A and AB) involving a gap between adjacent segments. For the latter two cases, we investigate the effect of the gap on the hydrodynamic force coefficients and the translational and rotational motions of the system. For all configurations, as the Reynolds number increases beyond 500, both the lift and drag coefficients decrease. Compared to a plain cylinder, a homogeneous fairing system (no gaps) can help reduce the drag force coefficient by 15 % for reduced velocity U* = 4.65, while a type A gap system can reduce the drag force coefficient by almost 50 % for reduced velocity U* = 3.5, 4.65, 6, and, correspondingly, the vibration response of the combined system, as well as the fairing rotation amplitude, are substantially reduced. For a homogeneous fairing, the cross-flow amplitude is reduced by about 80 %, whereas for fairings with a gap longer than half a cylinder diameter, VIVs are completely eliminated, resulting in additional reduction in the drag coefficient. We have related such VIV suppression or elimination to the features of the wake flow structure. We find that a gap causes the generation of strong streamwise vorticity in the gap region that interferes destructively with the vorticity generated by the fairings, hence disorganizing the formation of coherent spanwise cortical patterns. We provide visualization of the incoherent wake flow that leads to total elimination of the vibration and rotation of the fairing–cylinder system. Finally, we investigate the effect of the friction coefficient between cylinder and fairing. The effect overall is small, even when the friction coefficients of adjacent segments are different. In some cases the equilibrium positions of the fairings are rotated by a small angle on either side of the centreline, in a symmetry-breaking bifurcation, which depends strongly on Reynolds number. |
| first_indexed | 2024-09-23T10:29:47Z |
| format | Article |
| id | mit-1721.1/110825 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T10:29:47Z |
| publishDate | 2017 |
| publisher | Cambridge University Press |
| record_format | dspace |
| spelling | mit-1721.1/1108252024-06-26T20:29:43Z U-shaped fairings suppress vortex-induced vibrations for cylinders in cross-flow Yu, Yue Constantinides, Yiannis Karniadakis, George Em Xie, Fangfang Triantafyllou, Michael S Massachusetts Institute of Technology. Department of Mechanical Engineering Triantafyllou, Michael S. Xie, Fangfang Triantafyllou, Michael S We employ three-dimensional direct and large-eddy numerical simulations of the vibrations and flow past cylinders fitted with free-to-rotate U-shaped fairings placed in a cross-flow at Reynolds number 100 ⩽ Re ⩽ 10,000. Such fairings are nearly neutrally buoyant devices fitted along the axis of long circular risers to suppress vortex-induced vibrations (VIVs). We consider three different geometric configurations: a homogeneous fairing, and two configurations (denoted A and AB) involving a gap between adjacent segments. For the latter two cases, we investigate the effect of the gap on the hydrodynamic force coefficients and the translational and rotational motions of the system. For all configurations, as the Reynolds number increases beyond 500, both the lift and drag coefficients decrease. Compared to a plain cylinder, a homogeneous fairing system (no gaps) can help reduce the drag force coefficient by 15 % for reduced velocity U* = 4.65, while a type A gap system can reduce the drag force coefficient by almost 50 % for reduced velocity U* = 3.5, 4.65, 6, and, correspondingly, the vibration response of the combined system, as well as the fairing rotation amplitude, are substantially reduced. For a homogeneous fairing, the cross-flow amplitude is reduced by about 80 %, whereas for fairings with a gap longer than half a cylinder diameter, VIVs are completely eliminated, resulting in additional reduction in the drag coefficient. We have related such VIV suppression or elimination to the features of the wake flow structure. We find that a gap causes the generation of strong streamwise vorticity in the gap region that interferes destructively with the vorticity generated by the fairings, hence disorganizing the formation of coherent spanwise cortical patterns. We provide visualization of the incoherent wake flow that leads to total elimination of the vibration and rotation of the fairing–cylinder system. Finally, we investigate the effect of the friction coefficient between cylinder and fairing. The effect overall is small, even when the friction coefficients of adjacent segments are different. In some cases the equilibrium positions of the fairings are rotated by a small angle on either side of the centreline, in a symmetry-breaking bifurcation, which depends strongly on Reynolds number. 2017-07-24T18:41:23Z 2017-07-24T18:41:23Z 2015-10 2015-07 Article http://purl.org/eprint/type/JournalArticle 0022-1120 1469-7645 http://hdl.handle.net/1721.1/110825 Xie, Fangfang; Yu, Yue and Constantinides, Yiannis. “U-Shaped Fairings Suppress Vortex-Induced Vibrations for Cylinders in Cross-Flow.” Journal of Fluid Mechanics 782 (October 2015): 300–332 © 2015 Cambridge University Press https://orcid.org/0000-0002-4960-7060 en_US http://dx.doi.org/10.1017/jfm.2015.529 Journal of Fluid Mechanics Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf Cambridge University Press Prof. Triantafyllou via Angie Locknar |
| spellingShingle | Yu, Yue Constantinides, Yiannis Karniadakis, George Em Xie, Fangfang Triantafyllou, Michael S U-shaped fairings suppress vortex-induced vibrations for cylinders in cross-flow |
| title | U-shaped fairings suppress vortex-induced vibrations for cylinders in cross-flow |
| title_full | U-shaped fairings suppress vortex-induced vibrations for cylinders in cross-flow |
| title_fullStr | U-shaped fairings suppress vortex-induced vibrations for cylinders in cross-flow |
| title_full_unstemmed | U-shaped fairings suppress vortex-induced vibrations for cylinders in cross-flow |
| title_short | U-shaped fairings suppress vortex-induced vibrations for cylinders in cross-flow |
| title_sort | u shaped fairings suppress vortex induced vibrations for cylinders in cross flow |
| url | http://hdl.handle.net/1721.1/110825 https://orcid.org/0000-0002-4960-7060 |
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