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Zhongwu Jin
Department of River Engineering, Yangtze River Scientific Research Institute, Wuhan 430010, China

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Journal article
Published: 01 November 2019 in Journal of Marine Science and Engineering
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Because of special morphologies and complex runoff–tide interactions, the landward floodtide flows in Yangtze Estuary are observed to spill over from the North to the South Branches, carrying a lot of sediment. To quantitatively clarify the spillover problem, a two-dimensional numerical model using a high-resolution channel-refined unstructured grid is developed for the entire Yangtze Estuary from Datong to river mouths (620 km) and part of the East Sea. The developed model ensures a good description of the river-coast-ocean coupling, the irregular boundaries, and local river regimes in the Yangtze Estuary. In tests, the simulated histories of the tidal level, depth-averaged velocity, and sediment concentration agree well with field data. The spillover of sediment in the Yangtze Estuary is studied using the condition of a spring and a neap tide in dry seasons. For a representative cross-section in the upper reach of the North Branch (QLG), the difference of the cross-sectional sediment flux (CSSF) between floodtide and ebbtide durations is 43.85–11.26 × 104 t/day, accounting for 37.5–34.9% of the landward floodtide CSSF. The mechanics of sediment spillover in Yangtze Estuary are clarified in terms of a successive process comprising the source, transport, and drainage of the spillover sediment.

ACS Style

Dechao Hu; Min Wang; Shiming Yao; Zhongwu Jin. Study on the Spillover of Sediment during Typical Tidal Processes in the Yangtze Estuary Using a High-Resolution Numerical Model. Journal of Marine Science and Engineering 2019, 7, 390 .

AMA Style

Dechao Hu, Min Wang, Shiming Yao, Zhongwu Jin. Study on the Spillover of Sediment during Typical Tidal Processes in the Yangtze Estuary Using a High-Resolution Numerical Model. Journal of Marine Science and Engineering. 2019; 7 (11):390.

Chicago/Turabian Style

Dechao Hu; Min Wang; Shiming Yao; Zhongwu Jin. 2019. "Study on the Spillover of Sediment during Typical Tidal Processes in the Yangtze Estuary Using a High-Resolution Numerical Model." Journal of Marine Science and Engineering 7, no. 11: 390.

Technical note
Published: 23 September 2019 in Water
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A semi–implicit numerical model with a linear solver is proposed for the free-surface and pressurized mixed flows in hydraulic systems. It solves the two flow regimes within a unified formulation, and is much simpler than existing similar models for mixed flows. Using a local linearization and an Eulerian–Lagrangian method, the new model only needs to solve a tridiagonal linear system (arising from velocity-pressure coupling) and is free of iterations. The model is tested using various types of mixed flows, where the simulation results agree with analytical solutions, experiment data and the results reported by former researchers. Sensitivity studies of grid scales and time steps are both performed, where a common grid scale provides grid-independent results and a common time step provides time-step-independent results. Moreover, the model is revealed to achieve stable and accurate simulations at large time steps for which the CFL is greater than 1. In simulations of a challenging case (mixed flows characterized by frequent flow-regime conversions and a closed pipe with wide-top cross-sections), an artificial slot (A-slot) technique is proposed to cope with possible instabilities related to the discontinuous main-diagonal coefficients of the linear system. In this test, a slot-width sensitivity study is also performed, and the suitable slot-width ratio (ε) for the linear solver is suggested to be 0.05–0.1.

ACS Style

Dechao Hu; Songping Li; Shiming Yao; Zhongwu Jin. A Simple and Unified Linear Solver for Free-Surface and Pressurized Mixed Flows in Hydraulic Systems. Water 2019, 11, 1979 .

AMA Style

Dechao Hu, Songping Li, Shiming Yao, Zhongwu Jin. A Simple and Unified Linear Solver for Free-Surface and Pressurized Mixed Flows in Hydraulic Systems. Water. 2019; 11 (10):1979.

Chicago/Turabian Style

Dechao Hu; Songping Li; Shiming Yao; Zhongwu Jin. 2019. "A Simple and Unified Linear Solver for Free-Surface and Pressurized Mixed Flows in Hydraulic Systems." Water 11, no. 10: 1979.

Case report
Published: 12 July 2019 in Water
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Responses of irregular rotational tidal flows to an outlet regulation (the Guyuan Sand (GYS) regulation) in the three-level branching Yangtze Estuary are studied by a high-resolution numerical model and theoretical analysis. The project is launched around GYS at the outlet of the North Branch of the Yangtze Estuary. The tidal flows around GYS are rotational and become irregular under the influences of the runoff-tide interactions, rapidly varying topographies and complex solid boundaries in coastal areas. Three designs of GYS regulation were studied, including various diversion dikes and new outlets of different widths. The regulation disturbs the irregular rotational flows around GYS, and further changes the estuarine tidal processes and the water exchange between different branches of the branching Yangtze Estuary. It was interesting to find that additional current and additional storage are formed along the North Branch when a southward outlet and the clockwise rotational flow met around GYS. This special phenomenon is named “guide effect” in this study. The guide effect, together with common resist effect (arising from the narrowed outlet channel), reshapes the estuarine tidal processes. Based on the simulation result and a theoretical analysis, response mechanics of irregular rotational tidal flows to the outlet regulation in complex branching estuaries are quantitatively studied.

ACS Style

Dechao Hu; Min Wang; Shiming Yao; Zhongwu Jin; Hu; Wang; Yao; Jin. A Case Study: Response Mechanics of Irregular Rotational Tidal Flows to Outlet Regulation in Yangtze Estuary. Water 2019, 11, 1445 .

AMA Style

Dechao Hu, Min Wang, Shiming Yao, Zhongwu Jin, Hu, Wang, Yao, Jin. A Case Study: Response Mechanics of Irregular Rotational Tidal Flows to Outlet Regulation in Yangtze Estuary. Water. 2019; 11 (7):1445.

Chicago/Turabian Style

Dechao Hu; Min Wang; Shiming Yao; Zhongwu Jin; Hu; Wang; Yao; Jin. 2019. "A Case Study: Response Mechanics of Irregular Rotational Tidal Flows to Outlet Regulation in Yangtze Estuary." Water 11, no. 7: 1445.