Vortex pairs formed by tidal currents in the Naruto Strait: effects of bottom topography, density stratification, and coastline geometry

IF 1.3 4区 地球科学 Q4 OCEANOGRAPHY
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引用次数: 0

Abstract

Vortex pairs formed at a strait outlet by tidal flow effectively induce water exchange and material transport in coastal areas. However, the effects of complex bottom topography and density stratification remain unclear. Here, we investigated the development and propagation of vortex pairs in the Naruto Strait, which has complex topography. Satellite observations indicated that the vortex pairs formed on the northern side of the strait continue to move away from the strait after the reversal of tidal flow, shifting their propagation from northward to westward. Numerical experiments revealed that: (1) changes in depth affect the propagation speed and overall size of vortex pairs; (2) density stratification reduces the effects of depth changes; (3) coastline geometry affects the propagation direction of vortex pairs. Furthermore, experiments with idealized topography showed that in a region where depth increases with vortex-pair propagation, the jet decelerates, and the vortex pair shrinks in size. Conversely, in a region where depth decreases, the jet widens, and the vortex pair expands. The changes in jet flow speed can be attributed to flow continuity and depth change, as the latter alters the cross-sectional area. Meanwhile, the changes in vortex pair size and jet width can be explained by vortex propagation on a slope due to potential vorticity conservation. These effects of topography and density stratification may also be significant in other coastal areas and potentially influence the Strouhal number threshold below which vortex pairs leave an outlet.

鸣门海峡潮流形成的涡旋对:海底地形、密度分层和海岸线几何形状的影响
摘要 潮汐流在海峡出口处形成的涡对能有效地引起沿岸地区的水交换和物质迁移。然而,复杂的海底地形和密度分层的影响仍不清楚。在此,我们研究了鸣门海峡复杂地形中涡旋对的发展和传播。卫星观测结果表明,在海峡北侧形成的涡旋对在潮汐流逆转后继续远离海峡,传播方向由北向西移动。数值实验表明(1) 深度变化会影响涡旋对的传播速度和整体大小;(2) 密度分层会降低深度变化的影响;(3) 海岸线的几何形状会影响涡旋对的传播方向。此外,用理想化地形进行的实验表明,在深度随涡旋对传播而增加的区域,喷流会减速,涡旋对的大小会缩小。相反,在深度减小的区域,射流变宽,涡旋对扩大。射流流速的变化可归因于流动的连续性和深度变化,因为后者改变了横截面积。同时,涡旋对大小和射流宽度的变化可解释为潜在涡度守恒导致的涡旋在斜坡上的传播。这些地形和密度分层的影响在其它沿岸地区可能也很重要,并可能影响 Strouhal 数阈值,低于该阈值,涡旋对就会离开出口。
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来源期刊
Journal of Oceanography
Journal of Oceanography 地学-海洋学
CiteScore
3.50
自引率
13.00%
发文量
42
审稿时长
6-12 weeks
期刊介绍: The Journal of Oceanography is the official journal of the Oceanographic Society of Japan and open to all oceanographers in the world. The main aim of the journal is to promote understandings of ocean systems from various aspects including physical, chemical, biological, geological oceanography as well as paleoceanography, etc. The journal welcomes research focusing on the western North Pacific and Asian coastal waters, but the study region is not limited to the Asian Pacific. The journal publishes original articles, short contributions, reviews, and correspondence in oceanography and related fields.
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