Numerical Simulation of Tidal Waves Variation in the North Branch of the Changjiang Estuary

2013 ◽  
Vol 405-408 ◽  
pp. 1472-1475
Author(s):  
Jie Gu ◽  
Dan Qing Ma ◽  
Xin Qin ◽  
Xiao Li Wang ◽  
Ji Zhong Yang ◽  
...  
Keyword(s):  
Neap Tide ◽  
Spring Tide ◽  
Changjiang Estuary ◽  
Tidal Range ◽  
Level Curve ◽  
Middle Reach ◽  
Tidal Level ◽  
The Changjiang Estuary ◽  
The North ◽  
Set Up

A 2D numerical model about the Changjiang Estuary was set up with MIKE 21 in this study, which was well calibrated and verified with the observed tidal levels, flow velocities and flow directions, the computed results agree well with the measured data. Then the model has been applied to calculate the tidal level in the North Branch during spring and neap tide in flood season. The results show that, from the middle reach to the upper reach of the North Branch, the high tidal level is lower and lower and the low tidal level is upper and upper, so the tidal range is decreased, and tidal range during spring is greater than the one during neap. The tidal peak appearing time in the upper reach of the North Branch lags behind that of the middle reach, which is obviously during neap tide. The tidal level curve of the middle reach of the North Branch is smooth and close to the simple harmonic curve, while that of the upper reach of the North Branch deformities, the tidal level curve of ebb tide change fluctuant, much more obviously at spring tide.

Numerical Analysis of Ebb Water Split Ratio of the South and North Branch in the Changjiang Estuary

2013 ◽  
Vol 807-809 ◽  
pp. 1624-1627
Author(s):  
Ji Zhong Yang ◽  
Jie Gu ◽  
Dan Qing Ma ◽  
Xiao Li Wang ◽  
Tian Hu ◽  
...  
Keyword(s):  
Spring Tide ◽  
Changjiang Estuary ◽  
The South ◽  
The Changjiang Estuary ◽  
Hydrodynamic Analysis ◽  
The North ◽  
Split Ratio ◽  
Calculation Results ◽  
Set Up ◽  
The One

The change of water split ratio has important impacts on the fluvial process, saltwater intrusion and navigation in estuary area. A 2D hydrodynamics numerical model of the Changjiang Estuary was set up using Delft3D-FLOW. The calculation results are consistent well with the real measured data, which indicates that the model can be used in hydrodynamic analysis. Simulation results show that the ebb water split ratio of the North Branch in the flood season is larger than that in the dry season, while the situation of the South Branch is opposite. Under the condition of different tidal types, the ebb water split ratio for the North Branch is maximum during the spring tide, and minimum during the neap tide, while the one during the middle tide takes the second place.

scholarly journals Impacts of the Qingcaosha Reservoir on saltwater intrusion in the Changjiang Estuary

2021 ◽  
Vol 4 (1) ◽  
pp. 17-35
Author(s):  
Zhangliang Ding ◽  
Jianrong Zhu ◽  
Hanghang Lyu
Keyword(s):  
Saltwater Intrusion ◽  
Neap Tide ◽  
Spring Tide ◽  
Changjiang Estuary ◽  
Water Diversion ◽  
The Changjiang Estuary ◽  
The North ◽  
Salinity Increase ◽  
Hydrodynamic Processes ◽  
Changxing Island

The massive Qingcaosha Reservoir (QCSR) is located in the Changjiang Estuary along the northwest coast of Changxing Island. The reservoir significantly narrowed the upper reaches of the North Channel and deepened the channel near the reservoir. These topographical changes inevitably influenced hydrodynamic processes and saltwater intrusion in the estuary. A well-validated model was employed to investigate the influence of the QCSR on saltwater intrusion in the Changjiang Estuary. The model results showed that the narrowed upper reaches of the North Channel decreased the water diversion ratio and thus increased salinity in the North Channel. During the moderate tide after neap tide, the salinity decreased at the water intake of the QCSR because saltwater intrusion was obstructed at flood slack at the surface, while the salinity increase during the moderate tide after spring tide was mainly due to the intensified saltwater intrusion during spring tide. The deepening of the channel near the QCSR resulted in an increased water diversion ratio, and the salinity in the Eastern Chongming Shoal decreased by more than 0.5 psu during spring tide; however, the saltwater intrusion was enhanced due to the strengthened baroclinic force, which is proportional to the water depth. During neap tide, the salinity in the entire North Channel decreased because of a 1.4% increase in the water diversion ratio of the North Channel and the relatively weak tide.

scholarly journals Water and Salt Transports in the Hengsha Channel of Changjiang Estuary

2022 ◽  
Vol 10 (1) ◽  
pp. 72
Author(s):  
Rui Ma ◽  
Jianrong Zhu
Keyword(s):  
Water Transport ◽  
Neap Tide ◽  
Spring Tide ◽  
Dry Season ◽  
Changjiang Estuary ◽  
Dynamic Mechanism ◽  
Gradient Force ◽  
Residual Water ◽  
Wet Season ◽  
The North

In a multilevel bifurcated estuary, the channels between the bifurcated branches play important roles in the exchanges of water and salt. In the Changjiang Estuary, the Hengsha Channel (HC) connects the North Channel (NC) and the North Passage (NP). In this paper, based on a two-way nesting unstructured quadrilateral grid, finite-differencing, three-dimensional estuarine and coastal ocean model, the tidal and seasonal variations in the water and salt transports in the HC were simulated, and their dynamic mechanism was analyzed. The residual water and salt transports in the HC both flow southward from the NC to the NP. In wet season, the residual water transport in the HC is 677 m3/s during neap tide and 245 m3/s during spring tide, and the residual salt transport is 0. In dry season, the residual water and salt transports in the HC are 1278 m3/s and 0.38 t/s during neap tide, respectively, and 1328 m3/s and 12.61 t/s during spring tide. Affected by the northerly wind and the southeastward baroclinic gradient force, the water and salt fluxes in dry season are much larger than those in wet season. The dynamic mechanism responsible for the water transport in the HC was numerically simulated and analyzed.

scholarly journals The Transformation of Salinity Variance: A New Approach to Quantifying the Influence of Straining and Mixing on Estuarine Stratification

2018 ◽  
Vol 48 (3) ◽  
pp. 607-623 ◽  
Author(s):  
Xiangyu Li ◽  
W. Rockwell Geyer ◽  
Jianrong Zhu ◽  
Hui Wu
Keyword(s):  
Neap Tide ◽  
Salinity Gradient ◽  
Spring Tide ◽  
Changjiang Estuary ◽  
Spatial And Temporal Variability ◽  
General Tendency ◽  
The Changjiang Estuary ◽  
Tidal Straining ◽  
Variance Method ◽  
The One

AbstractThe roles of straining and dissipation in controlling stratification are derived analytically using a vertical salinity variance method. Stratification is produced by converting horizontal variance to vertical variance via straining, that is, differential advection of horizontal salinity gradients, and stratification is destroyed by the dissipation of vertical variance through turbulent mixing. A numerical model is applied to the Changjiang estuary in order to demonstrate the salinity variance balance and how it reveals the factors controlling stratification. The variance analysis reveals that dissipation reaches its maximum during spring tide in the Changjiang estuary, leading to the lowest stratification. Stratification increases from spring tide to neap tide because of the increasing excess of straining over dissipation. Throughout the spring–neap tidal cycle, straining is almost always larger than dissipation, indicating a net excess of production of vertical variance relative to dissipation. This excess is balanced on average by advection, which exports vertical variance out of the estuarine region into the plume. During neap tide, tidal straining shows a general tendency of destratification during the flood tide and restratification during ebb, consistent with the one-dimensional theory of tidal straining. During spring tide, however, positive straining occurs during flood because of the strong baroclinicity induced by the intensified horizontal salinity gradient. These results indicate that the salinity variance method provides a valuable approach for examining the spatial and temporal variability of stratification in estuaries and coastal environments.

The time-varying characteristics in tidal duration asymmetry

2020 ◽  
Author(s):  
Guo Wenyun ◽  
Song Dehai ◽  
Guo Leicheng ◽  
Ge Jianzhong ◽  
Ding Pingxing ◽  
...  
Keyword(s):  
Neap Tide ◽  
Spring Tide ◽  
Time Variability ◽  
Tidal Asymmetry ◽  
Water Effect ◽  
The Changjiang Estuary ◽  
Tidal Constituents ◽  
Sea Area ◽  
Tide Interaction ◽  
Shallow Water Effect

<p>Tides always behaves different rising and falling durations, which can mostly attribute to the shallow-water effect and interactions among tidal constituents. The duration asymmetry may lead to an inequality in flood/ebb tidal current magnitudes, affecting the net sediment transport. Tidal duration asymmetry has time-dependent characteristics. We deducted a general framework for identifying the time-variability in tidal duration asymmetry. The application to the global tides showed that the fortnightly variability in tidal asymmetry is universal and that duration asymmetry can be stronger during neap tide than during spring tide. Then the framework is applied to the tides in the Changjiang Estuary. Prominent seasonal variation in tidal asymmetry is revealed, mainly relate to the river-tide interaction. Application to the tides in the Yangshan Harbor sea area revealed that the local-scale tidal asymmetry can be changed strongly by a large coastal engineering.</p>

Mathematical tidal model of the Tay Estuary

1980 ◽  
Vol 78 (3-4) ◽  
pp. s171-s182
Author(s):  
D. J. A. Williams ◽  
V. Nassehi
Keyword(s):  
Mathematical Model ◽  
Finite Difference ◽  
Tidal Range ◽  
Level Curve ◽  
Tidal Level ◽  
Tidal Model ◽  
One Dimensional ◽  
Implicit Finite Difference Scheme ◽  
Implicit Finite Difference ◽  
Tay Estuary

SynopsisA one-dimensional mathematical model based on an implicit finite difference scheme is used to predict tidal levels and discharges throughout the Tay Estuary. The model accounts for the transformation of the tidal level curve along the estuary and predicts a maximum tidal range near Flisk. There is a measure of agreement between computed velocities and observed data in the upper reaches of the estuary.

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