Sediment dynamics near a sandy spit with wave-induced coastal currents

2021 ◽  
Author(s):  
Jing Lu
Keyword(s):  
Dominant Role ◽  
Three Dimensional ◽  
Separated Flow ◽  
Ocean Model ◽  
Sediment Dynamics ◽  
Coastal Current ◽  
Induced Current ◽  
Dominant Wave ◽  
Induced Currents ◽  
Wave Induced

<p>    Surface gravity waves play an important role in sediment transport. Previous studies have focused on the role of bottom shear enhanced by the surface wave orbital velocity. In this study, we embedded the University of New South Wales Sediment model into the Princeton Ocean Model, which includes a three-dimensional wave module to study sediment dynamics near a sandy spit in Sanniang Bay in the South China Sea. The simulated results for the deposition rate show that wave-induced currents play a dominant role in the maintenance of the sandy spit. The spit tip was formed as a result of the separation of wave-induced coastal flow. The spit tip was shown to be a barrier to the dominant wave-induced current, and the spit base was simulated to form via sand accumulation in the shelter of the spit tip. The deposition is mainly in the low-energy region behind the tip of the spit, which can counter the erosion effect of dominant wave-induced currents. The dominant wave-induced current prompts the lateral infilling of the spit tip when both the spit tip and base are above the water surface. The sediment carried by the coastal current is deposited along the flow branch of separation and forms the spit tip, which indicates that the sediment is deposited where the longshore current changes into an offshore current. As the water depth increases along the separated flow spindle, the bottom shear stress decreases, contributing to the deposition of the spit tip.</p>

scholarly journals Numerical simulation of the three-dimensional wave-induced currents on unstructured grid

2017 ◽  
Vol 31 (5) ◽  
pp. 539-548
Author(s):  
Ping Wang ◽  
Ning-chuan Zhang ◽  
Shuai Yuan ◽  
Wei-bin Chen
Keyword(s):  
Numerical Simulation ◽  
Unstructured Grid ◽  
Three Dimensional ◽  
Induced Currents ◽  
Wave Induced ◽  
Dimensional Wave

scholarly journals The circulation of Icelandic waters – a modelling study

Ocean Science ◽  
2013 ◽  
Vol 9 (5) ◽  
pp. 931-955 ◽  
Author(s):  
K. Logemann ◽  
J. Ólafsson ◽  
Á. Snorrason ◽  
H. Valdimarsson ◽  
G. Marteinsdóttir
Keyword(s):  
Three Dimensional ◽  
Atlantic Water ◽  
Volume Transport ◽  
Ocean Model ◽  
The Arctic ◽  
Coastal Current ◽  
Mean Flow ◽  
Model Code ◽  
The North ◽  
Icelandic Waters

Abstract. The three-dimensional flow, temperature and salinity fields of the North Atlantic, including the Arctic Ocean, covering the time period 1992 to 2006 are simulated with the numerical ocean model CODE. The simulation reveals several new insights and previously unknown structures which help us to clarify open questions on the regional oceanography of Icelandic waters. These relate to the structure and geographical distribution of the coastal current, the primary forcing of the North Icelandic Irminger Current (NIIC) and the path of the Atlantic Water south-east of Iceland. The model's adaptively refined computational mesh has a maximum resolution of 1 km horizontal and 2.5 m vertical in Icelandic waters. CTD profiles from this region and the river discharge of 46 Icelandic watersheds, computed by the hydrological model WaSiM, are assimilated into the simulation. The model realistically reproduces the established elements of the circulation around Iceland. However, analysis of the simulated mean flow field also provides further insights. It suggests a distinct freshwater-induced coastal current that only exists along the south-west and west coasts, which is accompanied by a counter-directed undercurrent. The simulated transport of Atlantic Water over the Icelandic shelf takes place in a symmetrical system of two currents, with the established NIIC over the north-western and northern shelf, and a hitherto unnamed current over the southern and south-eastern shelf, which is simulated to be an upstream precursor of the Faroe Current (FC). Both currents are driven by barotropic pressure gradients induced by a sea level slope across the Greenland–Scotland Ridge. The recently discovered North Icelandic Jet (NIJ) also features in the model predictions and is found to be forced by the baroclinic pressure field of the Arctic Front, to originate east of the Kolbeinsey Ridge and to have a volume transport of around 1.5 Sv within northern Denmark Strait. The simulated multi-annual mean Atlantic Water transport of the NIIC increased by 85% during 1992 to 2006, whereas the corresponding NIJ transport decreased by 27%. Based on our model results we propose a new and further differentiated circulation scheme of Icelandic waters whose details may inspire future observational oceanography studies.

scholarly journals PERMEABLE GROYNES: EXPERIMENTS AND PRACTICE IN THE NETHERLANDS

1984 ◽  
Vol 1 (19) ◽  
pp. 136 ◽  
Author(s):  
W.T. Bakker ◽  
C.H. Hulsbergen ◽  
P. Roelse ◽  
C. De Smit ◽  
J.N. Svasek
Keyword(s):  
The Netherlands ◽  
Protected Areas ◽  
Coastal Erosion ◽  
Statistical Significance ◽  
Coastal Current ◽  
Tidal Channels ◽  
Negative Experience ◽  
Model Experiments ◽  
Induced Currents ◽  
Wave Induced

This paper reports on model experiments and up to 20 years of practice in nature with a permeable groyne system, consisting of single or double permeable rows of wooden piles perpendicular to the beach, without bottom protection. This system costs only 10 to 25% of the impermeable stone groynes which have for centuries been used in the Netherlands. Model experiments confirm that wave-induced currents in the protected areas are reduced to 65%, and tidal currents even to 50%, depending on the pile screen configuration. Prototype measurements could not lead to straightforward conclusions with statistical significance: the effect of the pile screens on beach evolution is partly merged into natural fluctuations and trends. Wooden pile screens do not prevent the shoreward motion of tidal channels, which can cause washing out of piles. Furthermore, constructional failures, which in the future can be avoided, at some places resulted in negative experience. It is concluded that permeable pile screens deserve serious consideration as a first flexible and cheap phase in combating coastal erosion. Its application however should be based on a thorough analysis of the local coastal current climate.

scholarly journals Iteration Coupling Simulation of Random Waves and Wave-Induced Currents

2012 ◽  
Vol 2012 ◽  
pp. 1-13
Author(s):  
Jinhai Zheng ◽  
Tianwen Wang ◽  
Gang Wang ◽  
Chenming Zhang ◽  
Chi Zhang
Keyword(s):  
Wave Field ◽  
Circulation Model ◽  
Wave Transformation ◽  
Induced Current ◽  
Random Waves ◽  
Three Dimensional Model ◽  
Current Interaction ◽  
Induced Currents ◽  
Coupling Algorithm ◽  
Wave Induced

A two-way coupling algorithm for wave-current interaction is developed and implemented into a nearshore circulation model to investigate the effects of fully wave-current interaction on irregular wave transformation over an elliptic shoal. The wave field is simulated by a spectral wave model WABED, and the wave-induced current is solved by a quasi-three-dimensional model WINCM. The surface roller effects are represented in the formulation of surface stress, and the roller characteristics are solved by a roller evolution model. The proposed two-way coupling algorithm can describe both the generation of wave-induced current and the current-induced wave transformation, which is more physically reasonable than the one-way approaches. The model test with a laboratory experiment shows that wave-induced currents have an important influence on the wave transformation, for example, the wave energy defocusing due to the strong jet-like current along the centerline of the shoal. It is revealed that the accuracy of simulated wave field can be significantly improved by taking into account the two-way wave-current interaction.

scholarly journals The circulation of Icelandic waters – a modelling study

2013 ◽  
Vol 10 (2) ◽  
pp. 763-824 ◽  
Author(s):  
K. Logemann ◽  
J. Ólafsson ◽  
Á. Snorrason ◽  
H. Valdimarsson ◽  
G. Marteinsdóttir
Keyword(s):  
Pressure Field ◽  
Three Dimensional ◽  
Atlantic Water ◽  
Ocean Model ◽  
The Arctic ◽  
Coastal Current ◽  
Mean Flow ◽  
The South ◽  
The North ◽  
Icelandic Waters

Abstract. The three-dimensional flow, temperature and salinity fields of the North Atlantic including the Arctic Ocean covering the time period 1992 to 2006 are simulated with the numerical ocean model CODE. The model reveals several new insights and previously unknown structures which help us to clarify open questions on the regional oceanography of Icelandic waters. These relate to the structure and geographical distribution of the coastal current, the primary forcing of the North Icelandic Irminger Current (NIIC), the path of the Atlantic Water south-east of Iceland and the structure of the North Icelandic Jet (NIJ). The model's adaptively refined computational mesh has a maximum resolution of 1 km horizontal and 2.5 m vertical in Icelandic waters. CTD profiles from this region and the river discharge of 46 Icelandic watersheds, computed by the hydrological model WaSiM, are assimilated into the simulation. The model realistically reproduces the established elements of the circulation around Iceland. However, analysis of the simulated mean flow field also provides further insights. It suggests a distinct freshwater-induced coastal current that only exists along the south-west and west coasts which is accompanied by a counter-directed undercurrent. The simulated transport of Atlantic Water over the Icelandic shelf takes place in a symmetrical system of two currents, with the established NIIC over the north-western and northern shelf, and a current over the southern and south-eastern shelf herein called the South Icelandic Current (SIC). Both currents are driven by topographically induced distortions of the Arctic Front's barotropic pressure field. The SIC is simulated to be an upstream precursor of the Faroe Current (FC). The recently discovered North Icelandic Jet (NIJ) also features in the model predictions and is found to be forced by the baroclinic pressure field of the Arctic Front, to originate east of the Kolbeinsey Ridge and to have a volume transport of around 1.5 Sv within northern Denmark Strait. The simulated multi-annual mean Atlantic Water transport of the NIIC increased by 85% during 1992 to 2006, whereas the corresponding NIJ transport decreased by 27%. Based on our model results we propose a new and further differentiated circulation scheme of Icelandic waters whose details may inspire future observational oceanography studies.

scholarly journals Assessment of Computational Fluid Dynamics Capabilities for the Prediction of Three-Dimensional Separated Flows: The DELFT 372 Catamaran in Static Drift Conditions

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
R. Broglia ◽  
S. Zaghi ◽  
E. F. Campana ◽  
T. Dogan ◽  
H. Sadat-Hosseini ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Separated Flow ◽  
Lateral Force ◽  
Separated Flows ◽  
Overlapping Grids ◽  
Wave Induced

In this paper, capabilities of state-of-the-art computational fluid dynamics (CFD) tools in the prediction of the flow-field around a multihull catamaran advancing in straight ahead motion at nonzero drift angles are investigated. CFD estimations have been provided by three research institutes by using their in-house codes: CNR-INM using Xnavis, IIHR using CFDShip-Iowa, and CNRS/ECN using ISIS. These allowed an in-depth comparison between different methodologies, such as structured overlapping grids versus unstructured grid, different turbulence models and detached eddy simulations (DES) approaches, and level-set (LS) versus volume of fluid (VoF). The activities were pursued within the NATO AVT-183 group “reliable prediction of separated flow onset and progression for air and sea vehicles,” aimed at the assessment of CFD predictions of large three-dimensional separated flows. Comparison between estimations is provided for both integral and local quantities, and for wave-induced vortices. Validation is reported by comparison against the available experimental fluid dynamics (EFD) data. Generally, all the simulations are able to capture the main features of the flow field; grid resolution effects are dominant in the onset phase of coherent structures and turbulence model affects the dynamic of the vortices. Hydrodynamic loads are in agreement between the submissions with standard deviation of about 3.5% for the resistance prediction and about 7% for lateral force and yaw moment estimation. Wave-induced vortices are correctly captured by both LS and VoF approaches, even if some differences have been highlighted, LS showing well-defined and long life vortices.

scholarly journals Generation of a Buoyancy-Driven Coastal Current by an Antarctic Polynya

2008 ◽  
Vol 38 (5) ◽  
pp. 1011-1032 ◽  
Author(s):  
Alexander V. Wilchinsky ◽  
Daniel L. Feltham
Keyword(s):  
Numerical Models ◽  
Three Dimensional ◽  
Ocean Model ◽  
Ocean Modeling ◽  
Coastal Current ◽  
Convex Shape ◽  
High Salinity Water ◽  
Variable Bottom ◽  
Coastal Polynya ◽  
Salinity Water

Abstract Descent and spreading of high salinity water generated by salt rejection during sea ice formation in an Antarctic coastal polynya is studied using a hydrostatic, primitive equation three-dimensional ocean model called the Proudman Oceanographic Laboratory Coastal Ocean Modeling System (POLCOMS). The shape of the polynya is assumed to be a rectangle 100 km long and 30 km wide, and the salinity flux into the polynya at its surface is constant. The model has been run at high horizontal spatial resolution (500 m), and numerical simulations reveal a buoyancy-driven coastal current. The coastal current is a robust feature and appears in a range of simulations designed to investigate the influence of a sloping bottom, variable bottom drag, variable vertical turbulent diffusivities, higher salinity flux, and an offshore position of the polynya. It is shown that bottom drag is the main factor determining the current width. This coastal current has not been produced with other numerical models of polynyas, which may be because these models were run at coarser resolutions. The coastal current becomes unstable upstream of its front when the polynya is adjacent to the coast. When the polynya is situated offshore, an unstable current is produced from its outset owing to the capture of cyclonic eddies. The effect of a coastal protrusion and a canyon on the current motion is investigated. In particular, due to the convex shape of the coastal protrusion, the current sheds a dipolar eddy.

scholarly journals Relationship between Three-Dimensional Radiation Stress and Vortex-Force Representations

2021 ◽  
Vol 9 (8) ◽  
pp. 791
Author(s):  
Duoc Tan Nguyen ◽  
Ad J. H. M. Reniers ◽  
Dano Roelvink
Keyword(s):  
Three Dimensional ◽  
Ocean Model ◽  
Radiation Stress ◽  
Mean Motion ◽  
Numerical Ocean Model ◽  
The Mean ◽  
Ocean Models ◽  
Wave Induced ◽  
Mean Current

In numerical ocean models, the effect of waves on currents is usually expressed by either vortex-force or radiation stress representations. In this paper, the differences and similarities between those two representations are investigated in detail in conditions of both conservative and nonconservative waves. In addition, comparisons between different sets of equations of mean motion that apply different representations of wave-induced forcing terms are included. The comparisons are useful for selecting a suitable numerical ocean model to simulate the mean current in conditions of waves combined with currents.

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