Longshore Current Profiles and Instabilities on Plane Beaches with Mild Slopes
The accurate determination of cross-shore longshore current profiles in the surf zone is essentially important in understanding of coastal physical processes and modelling of longshore sediment transport. In this study, a comprehensive laboratory study was undertaken to directly measure longshore cu...
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| Format: | Article |
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MDPI AG
2023-01-01
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| Series: | Journal of Marine Science and Engineering |
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| Online Access: | https://www.mdpi.com/2077-1312/11/1/172 |
| _version_ | 1827624269011484672 |
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| author | Sheng Yan Zhili Zou Dong Wang Zaijin You |
| author_facet | Sheng Yan Zhili Zou Dong Wang Zaijin You |
| author_sort | Sheng Yan |
| collection | DOAJ |
| description | The accurate determination of cross-shore longshore current profiles in the surf zone is essentially important in understanding of coastal physical processes and modelling of longshore sediment transport. In this study, a comprehensive laboratory study was undertaken to directly measure longshore current profiles over plane beaches with two mild slopes, 1:40 and 1:100, in a wave basin 55 m long, 34 m wide, and 0.7 m deep. Different wave conditions with an incidence angle of 30° were generated by piston-type wave makers consisting of 70 individual paddles, and two arrays of 29 Acoustic Doppler Velocimeters (ADVs) were used to measure longshore currents in the surf zone. Based on the experimental data collected in this study, three types of cross-shore longshore current profiles were found on the two plane beaches under different testing wave conditions, namely quasi-Rayleigh, quasi-Gaussian, and M-shape profiles. The quasi-Rayleigh profile was found on the beach slope of 1:40, and the other two types were found on the beach slope of 1:100. Analytical formulae were proposed to describe these profiles and agreed well with the laboratory data. The fluctuations of longshore currents observed in this study were attributed to their shear instabilities based on linear instability analysis. The results of the linear instability analysis and the spectra of measured velocities also showed that the three types of velocity profiles led to different instability characteristics. |
| first_indexed | 2024-03-09T12:05:23Z |
| format | Article |
| id | doaj.art-1f39cd0e1c98499db9383cca8cd5fe19 |
| institution | Directory Open Access Journal |
| issn | 2077-1312 |
| language | English |
| last_indexed | 2024-03-09T12:05:23Z |
| publishDate | 2023-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Journal of Marine Science and Engineering |
| spelling | doaj.art-1f39cd0e1c98499db9383cca8cd5fe192023-11-30T22:58:10ZengMDPI AGJournal of Marine Science and Engineering2077-13122023-01-0111117210.3390/jmse11010172Longshore Current Profiles and Instabilities on Plane Beaches with Mild SlopesSheng Yan0Zhili Zou1Dong Wang2Zaijin You3College of Transportation Engineering, Dalian Maritime University, Dalian 116026, ChinaState Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, ChinaCollege of Environmental Science and Engineering, Dalian Maritime University, Dalian 116026, ChinaCollege of Transportation Engineering, Dalian Maritime University, Dalian 116026, ChinaThe accurate determination of cross-shore longshore current profiles in the surf zone is essentially important in understanding of coastal physical processes and modelling of longshore sediment transport. In this study, a comprehensive laboratory study was undertaken to directly measure longshore current profiles over plane beaches with two mild slopes, 1:40 and 1:100, in a wave basin 55 m long, 34 m wide, and 0.7 m deep. Different wave conditions with an incidence angle of 30° were generated by piston-type wave makers consisting of 70 individual paddles, and two arrays of 29 Acoustic Doppler Velocimeters (ADVs) were used to measure longshore currents in the surf zone. Based on the experimental data collected in this study, three types of cross-shore longshore current profiles were found on the two plane beaches under different testing wave conditions, namely quasi-Rayleigh, quasi-Gaussian, and M-shape profiles. The quasi-Rayleigh profile was found on the beach slope of 1:40, and the other two types were found on the beach slope of 1:100. Analytical formulae were proposed to describe these profiles and agreed well with the laboratory data. The fluctuations of longshore currents observed in this study were attributed to their shear instabilities based on linear instability analysis. The results of the linear instability analysis and the spectra of measured velocities also showed that the three types of velocity profiles led to different instability characteristics.https://www.mdpi.com/2077-1312/11/1/172longshore current profilesplane beachesshear instabilities |
| spellingShingle | Sheng Yan Zhili Zou Dong Wang Zaijin You Longshore Current Profiles and Instabilities on Plane Beaches with Mild Slopes Journal of Marine Science and Engineering longshore current profiles plane beaches shear instabilities |
| title | Longshore Current Profiles and Instabilities on Plane Beaches with Mild Slopes |
| title_full | Longshore Current Profiles and Instabilities on Plane Beaches with Mild Slopes |
| title_fullStr | Longshore Current Profiles and Instabilities on Plane Beaches with Mild Slopes |
| title_full_unstemmed | Longshore Current Profiles and Instabilities on Plane Beaches with Mild Slopes |
| title_short | Longshore Current Profiles and Instabilities on Plane Beaches with Mild Slopes |
| title_sort | longshore current profiles and instabilities on plane beaches with mild slopes |
| topic | longshore current profiles plane beaches shear instabilities |
| url | https://www.mdpi.com/2077-1312/11/1/172 |
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