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Kelvin-Helmholtz Billows Induced by Shear Instability along the North Passage of the Yangtze River Estuary, China

1
Key Laboratory of Coastal Disaster and Defence (Hohai University), Ministry of Education, Nanjing 210098, China
2
College of Harbor, Coastal and Offshore Engineering, Hohai University, Nanjing 210098, China
3
Nanjing Hydraulic Research Institute, Nanjing 210024, China
*
Authors to whom correspondence should be addressed.
J. Mar. Sci. Eng. 2019, 7(4), 92; https://doi.org/10.3390/jmse7040092
Received: 14 February 2019 / Revised: 17 March 2019 / Accepted: 27 March 2019 / Published: 2 April 2019
(This article belongs to the Section Ocean Engineering)
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Abstract

Kelvin-Helmholtz (K-H) instability plays a significant role in mixing. To investigate the existence of K-H instability along the North Passage of the Yangtze River Estuary, the non-hydrostatic model NHWAVE is utilized to simulate the fresh-salt water mixing process along the North Passage of the Yangtze River Estuary. Using high horizontal resolution, the structure of K-H billows have been successfully captured within the Lower Reach of the North Passage. The K-H instability occurs between the max flood and high-water slack. The duration and length scale of the K-H billows highly depends on the local interaction between fresh-water discharge and tide. The horizontal length scale of the instability is about 60 m, similar to the observations in other estuaries. In the vertical direction, the K-H billows exist within the pycnocline with length scale ranging from 6 to 7 m. The timescale of the billows is approximate 6 min. By analyzing the changes of potential energy during the mixing process, results show that the existence of K-H instability induces intense vertical mixing, which can greatly increase mixing efficiency in the North Passage of the Yangtze River Estuary. View Full-Text
Keywords: non-hydrostatic wave model; Kelvin-Helmholtz (K-H) instability; salt-fresh water mixing; Yangtze River Estuary non-hydrostatic wave model; Kelvin-Helmholtz (K-H) instability; salt-fresh water mixing; Yangtze River Estuary
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Shi, J.; Tong, C.; Zheng, J.; Zhang, C.; Gao, X. Kelvin-Helmholtz Billows Induced by Shear Instability along the North Passage of the Yangtze River Estuary, China. J. Mar. Sci. Eng. 2019, 7, 92.

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