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https://hdl.handle.net/20.500.14094/90004437
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2024-04-30
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90004437 (fulltext)
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メタデータID
90004437
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open access
出版タイプ
Version of Record
タイトル
Three-dimensional transient rip currents: Bathymetric excitation of low-frequency intrinsic variability
著者
Uchiyama, Yusuke ; McWilliams, James C. ; Akan, Cigdem
著者ID
A0968
研究者ID
1000080344315
KUID
https://kuid-rm-web.ofc.kobe-u.ac.jp/search/detail?systemId=321466d484cf497c520e17560c007669
著者名
Uchiyama, Yusuke
内山, 雄介
ウチヤマ, ユウスケ
所属機関名
工学研究科
著者名
McWilliams, James C.
著者名
Akan, Cigdem
収録物名
Journal of Geophysical Research: Oceans
巻(号)
122(7)
ページ
5826-5849
出版者
American Geophysical Union (AGU)
刊行日
2017-07
公開日
2018-02-01
抄録
The ROMS-WEC model [Uchiyama et al., 2010] based on an Eulerian wave-averaged vortex-force asymptotic theory of McWilliams et al. (2004) is applied to analyze 3-D transient wave-driven rip currents and associated intrinsic very low-frequency (VLF) variability in the surf zone on a surveyed bathymetry under spatiotemporally uniform offshore incident waves. The 3-D rip currents are substantially depth-dependent due to the vertical recirculation, composed of pairs of counter-rotating longitudinal overturning roll cells that promote surface convergence. The vortex force plays an important role in vorticity budget, preconditioning overall vorticity reduction. These rip currents are intrinsically unstable and contribute about 70% to kinetic energy (KE) as eddy kinetic energy (EKE), consistent with observations. The dominant fluctuation period fits the VLF band, at about 18 min. The current effect on waves (CEW) alters not only the mean rip structure, but also the associated turbulence as the modified cross-shore EKE profile with considerable accentuation in the inner surf zone. Increased alongshore bathymetric variability proportionally intensifies KE and intrinsic EKE, whereas it reduces the VLF period. With a guide of a pseudo 2D model, we reveal that vortex tilting effect due to the horizontal vorticity inherent in the 3-D rip currents promotes collapse of the 3-D eddies through an enhanced forward kinetic energy cascade, leading to short-lived, laterally-stretched 3-D eddies resulting in elongated filaments that decay more quickly than coherent, long-lived, circular 2-D eddies.
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工学研究科
学術雑誌論文
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©2017. American Geophysical Union
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資源タイプ
journal article
言語
English (英語)
ISSN
2169-9275
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eISSN
2169-9291
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関連情報
DOI
https://doi.org/10.1002/2017JC013005
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