Blade dynamics in combined waves and current
Submerged aquatic vegetation (SAV), such as seagrass, is flexible and reconfigures (bends) in response to waves and current. The blade motion and reconfiguration modify the hydrodynamic drag. The modified drag can be described by an effective blade length, l e , which is defined as the length of a r...
| Main Authors: | , |
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| Other Authors: | |
| Format: | Article |
| Language: | English |
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Elsevier BV
2020
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| Online Access: | https://hdl.handle.net/1721.1/126720 |
| _version_ | 1826214646796779520 |
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| author | Lei, Jiarui Nepf, Heidi |
| author2 | Massachusetts Institute of Technology. Department of Civil and Environmental Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Civil and Environmental Engineering Lei, Jiarui Nepf, Heidi |
| author_sort | Lei, Jiarui |
| collection | MIT |
| description | Submerged aquatic vegetation (SAV), such as seagrass, is flexible and reconfigures (bends) in response to waves and current. The blade motion and reconfiguration modify the hydrodynamic drag. The modified drag can be described by an effective blade length, l e , which is defined as the length of a rigid blade that results in the same drag as a flexible blade of length l. In many natural settings SAV is exposed to combinations of waves and current. This study derived and used laboratory measurements to validate new predictions of effective blade length for combined waves and current based on a Cauchy number, which describes the ratio of hydrodynamic drag to the restoring force due to rigidity of blade. Force measurements on and digital images of blades exposed to waves with a 2-s period and with a range of wave velocity (U w ) and current speed (U c ) were used to estimate the effective blade length. The measurements were also used to validate a numerical simulation of blade motion. Once validated, the simulation was used to expand the investigated parameter space to a wider range of wave conditions, and in particular longer wave periods. ForU c <[Formula presented]U w , the blade motion and hydrodynamic drag were wave-dominated. For U c >2U w , the blade motion and hydrodynamic drag were current-dominated. |
| first_indexed | 2024-09-23T16:08:48Z |
| format | Article |
| id | mit-1721.1/126720 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T16:08:48Z |
| publishDate | 2020 |
| publisher | Elsevier BV |
| record_format | dspace |
| spelling | mit-1721.1/1267202022-09-29T18:33:32Z Blade dynamics in combined waves and current Lei, Jiarui Nepf, Heidi Massachusetts Institute of Technology. Department of Civil and Environmental Engineering Submerged aquatic vegetation (SAV), such as seagrass, is flexible and reconfigures (bends) in response to waves and current. The blade motion and reconfiguration modify the hydrodynamic drag. The modified drag can be described by an effective blade length, l e , which is defined as the length of a rigid blade that results in the same drag as a flexible blade of length l. In many natural settings SAV is exposed to combinations of waves and current. This study derived and used laboratory measurements to validate new predictions of effective blade length for combined waves and current based on a Cauchy number, which describes the ratio of hydrodynamic drag to the restoring force due to rigidity of blade. Force measurements on and digital images of blades exposed to waves with a 2-s period and with a range of wave velocity (U w ) and current speed (U c ) were used to estimate the effective blade length. The measurements were also used to validate a numerical simulation of blade motion. Once validated, the simulation was used to expand the investigated parameter space to a wider range of wave conditions, and in particular longer wave periods. ForU c <[Formula presented]U w , the blade motion and hydrodynamic drag were wave-dominated. For U c >2U w , the blade motion and hydrodynamic drag were current-dominated. 2020-08-21T13:55:41Z 2020-08-21T13:55:41Z 2019-05 2020-08-19T17:45:58Z Article http://purl.org/eprint/type/JournalArticle 0889-9746 https://hdl.handle.net/1721.1/126720 Lei, Jiarui and Heidi Nepf. "Blade dynamics in combined waves and current." Journal of Fluids and Structures 87 (May 2019): 137-149 © 2019 Elsevier Ltd en http://dx.doi.org/10.1016/j.jfluidstructs.2019.03.020 Journal of Fluids and Structures Creative Commons Attribution-NonCommercial-NoDerivs License http://creativecommons.org/licenses/by-nc-nd/4.0/ application/pdf Elsevier BV Prof. Nepf via Elizabeth Soergel |
| spellingShingle | Lei, Jiarui Nepf, Heidi Blade dynamics in combined waves and current |
| title | Blade dynamics in combined waves and current |
| title_full | Blade dynamics in combined waves and current |
| title_fullStr | Blade dynamics in combined waves and current |
| title_full_unstemmed | Blade dynamics in combined waves and current |
| title_short | Blade dynamics in combined waves and current |
| title_sort | blade dynamics in combined waves and current |
| url | https://hdl.handle.net/1721.1/126720 |
| work_keys_str_mv | AT leijiarui bladedynamicsincombinedwavesandcurrent AT nepfheidi bladedynamicsincombinedwavesandcurrent |