scholarly journals A Study on the Response of the Hydrodynamic Environment to the Morphology of Radial Sand Ridges in the Coastal Waters of Jiangsu

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2190
Author(s):  
Changjun Qi ◽  
Lejun Ma ◽  
Qinggai Wang ◽  
Yuan Zhai ◽  
Jixuan Li ◽  
...  
Keyword(s):  
Tidal Current ◽  
Unstructured Grid ◽  
Tidal Currents ◽  
Current Data ◽  
Material Transport ◽  
Current Field ◽  
Sand Ridges ◽  
Radial Sand Ridges ◽  
Local Current ◽  
Hydrodynamic Environment

A two-dimensional hydrodynamic model for the waters off the coast of Jiangsu, where there are radial sand ridges (RSRs) (hereinafter, the RSR area), was established based on measured topographic, tide level and tidal current data. Considering the complex topographic and geomorphic characteristics of the RSR group in this area, an unstructured grid was used for the calculation. A four-layer refinement was applied to the grid from outside to inside to better fit the complex topography. The simulations were performed to examine the response of the hydrodynamic environment to the morphology of the RSRs in three scenarios, namely, when there are natural RSRs, no RSRs, and partially reclaimed RSRs. When there are no or partially reclaimed RSRs, the tidal current field still exists in a radial pattern in the RSR area. The radial tidal current field is relatively stable and is not controlled by the morphologies of the RSRs. The topographic changes do not alter the distribution pattern of the radial tidal current field but do affect the local current fields. When there are no RSRs, the flood currents can directly reach Jianggang. Under practical conditions, the RSRs block the tidal currents during a flood tide to some extent. This phenomenon is particularly pronounced when the RSRs are partially reclaimed. For example, during an ebb tide, when the tidal currents encounter sand ridges or reclamation areas, their streamlines bend, and they flow around the obstacles. This change will affect the material transport, sediment deposition and seabed erosion.

Numerical Study on the Initial Formation of the Radial Sand Ridges

2014 ◽  
Vol 641-642 ◽  
pp. 222-225
Author(s):  
Sheng Song Zhang ◽  
Yu Li ◽  
Cao Hu
Keyword(s):  
Numerical Model ◽  
Tidal Current ◽  
Numerical Study ◽  
Current Field ◽  
Maintenance Mechanism ◽  
The Southern Yellow Sea ◽  
Sand Ridges ◽  
Radial Sand Ridges ◽  
Long Time ◽  
Formation And Evolution

The radial sand ridges located in the southern Yellow Sea off the Jiangsu coast, are unique sand ridges. They are characterized by radical current field and radical arrangement. The formation and maintenance mechanism of the radial sand ridges have always been a focus of attention of scholars for a long time. The formation is related to the unique convergent-divergent tidal currents. In this paper, a numerical model is constructed to answer the two following questions. Firstly, can the radial sand ridges be formed with radical tidal current field? Secondly, can this be simulated by a numerical model? The radial tidal current can shape the radial sand ridges. Numerical simulations show that the radial sand ridges can be formed on present radical tidal current field and the formation and evolution of the radial sand ridges can be simulated by a numerical model.

scholarly journals Australian tidal currents – assessment of a barotropic model (COMPAS v1.3.0 rev6631) with an unstructured grid

2021 ◽  
Vol 14 (9) ◽  
pp. 5561-5582
Author(s):  
David A. Griffin ◽  
Mike Herzfeld ◽  
Mark Hemer ◽  
Darren Engwirda
Keyword(s):  
Tidal Current ◽  
Unstructured Grid ◽  
Tide Gauge ◽  
Major Axis ◽  
Absolute Error ◽  
Tidal Currents ◽  
Practical Significance ◽  
Tidal Range ◽  
Validation Dataset ◽  
Velocity Amplitude

Abstract. While the variations of tidal range are large and fairly well known across Australia (less than 1 m near Perth but more than 14 m in King Sound), the properties of the tidal currents are not. We describe a new regional model of Australian tides and assess it against a validation dataset comprising tidal height and velocity constituents at 615 tide gauge sites and 95 current meter sites. The model is a barotropic implementation of COMPAS, an unstructured-grid primitive-equation model that is forced at the open boundaries by TPXO9v1. The mean absolute error (MAE) of the modelled M2 height amplitude is 8.8 cm, or 12 % of the 73 cm mean observed amplitude. The MAE of phase (10∘), however, is significant, so the M2 mean magnitude of vector error (MMVE, 18.2 cm) is significantly greater. The root sum square over the eight major constituents is 26 % of the observed amplitude. We conclude that while the model has skill at height in all regions, there is definitely room for improvement (especially at some specific locations). For the M2 major axis velocity amplitude, the MAE across the 95 current meter sites, where the observed amplitude ranges from 0.1 to 156 cm s−1, is 6.9 cm s−1, or 22 % of the 31.7 cm s−1 observed mean. This nationwide average result is encouraging, but it conceals a very large regional variation. Relative errors of the tidal current amplitudes on the narrow shelves of New South Wales (NSW) and Western Australia exceed 100 %, but tidal currents are weak and negligible there compared to non-tidal currents, so the tidal errors are of little practical significance. Looking nationwide, we show that the model has predictive value for much of the 79 % of Australia's shelf seas where tides are a major component of the total velocity variability. In descending order this includes the Bass Strait, the Kimberley to Arnhem Land, and southern Great Barrier Reef regions. There is limited observational evidence to confirm that the model is also valuable for currents in other regions across northern Australia. We plan to commence publishing “unofficial” tidal current predictions for chosen regions in the near future based on both our COMPAS model and the validation dataset we have assembled.

scholarly journals COMPARISON OF TIDAL CURRENTS UNDER DIFFERENT NOURISHMENT SCHEMES ON WEST BEACH OF BEIDAIHE, CHINA

2011 ◽  
Vol 1 (32) ◽  
pp. 32 ◽  
Author(s):  
Yu Zhang ◽  
Cuiping Kuang ◽  
Lulu He ◽  
Yi Pan ◽  
Yanxiong Yang ◽  
...  
Keyword(s):  
Numerical Model ◽  
Shallow Water Equations ◽  
Tidal Current ◽  
Unstructured Grid ◽  
Field Survey ◽  
Tidal Level ◽  
Current Field ◽  
Primary Analysis ◽  
Project Area ◽  
Tidal Current Velocity

This paper detailed a study on the tidal current field around a beach nourishment project including submerged breakwaters and jetties. The effect of different nearshore structure arrangements on the tidal current field was studied utilizing a numerical model build based on the solution of two-dimensional shallow water equations and an unstructured grid. In order to calibrate the numerical model, field survey was conducted at 5 current stations and a tidal level station around the project area. According to a primary analysis on stability, environment, sight of the beach, and construction quantity, four project schemes were chosen and simulated. After comparing the modeling results, the effects of submerged breakwaters and jetties were discussed. Conclusively, it is feasible to protect the filled sand on west beach by jetties and submerged breakwaters through obvious tidal current velocity reduction in the nearshore area.

scholarly journals Seabed disturbance and sediment mobility due to tidal current and waves on the continental shelves of Canada

2021 ◽  
Author(s):  
Michael Z. Li ◽  
Yongsheng Wu ◽  
Charles Gordon Hannah ◽  
William A. Perrie
Keyword(s):  
Tidal Current ◽  
Transport Model ◽  
Tidal Currents ◽  
Current Data ◽  
Shear Stresses ◽  
Shelf Area ◽  
Medium Sand ◽  
Continental Shelves ◽  
Sediment Mobility ◽  
Sediment Mobilization

Waves and tidal currents can interact to produce strong seabed shear stress and mobilization of sediments on continental shelves. Modelled wave and tidal current data for a 3-year period were used in a combined-flow sediment transport model to simulate the seabed shear stresses and the mobilization of uniform medium sand on the continental shelves of Canada. The modelling results are presented to establish the first national framework of seabed disturbance and sediment mobility on the continental shelves of Canada. Strong waves and tidal currents on the Canadian continental shelves produce mean bed shear velocity >5 cm·s<sup>−1</sup>. Medium sand can be mobilized >50% of the time over many areas on the shelves. The mobilization by tidal currents occurs over 36% and by waves over 50% of the shelf area, demonstrating that mobilization of sediments is dominated by waves on the Canadian continental shelves. Combined shear stresses due to wave and tidal current interaction further increase sediment mobilization to over 68% of the shelf area. The spatial variation of the relative importance of wave and tidal disturbances allows classification of the continental shelves into six disturbance types. Innovative Seabed Disturbance (SDI) and Sediment Mobility (SMI) indices are proposed to quantify the seabed exposure to oceanographic processes and sediment mobilization, incorporating both the magnitude and frequency of these processes. The proposed SDI and SMI, together with the disturbance type classification, can be used as standard parameters to best quantify seabed disturbance and sediment mobility on other shelves of the world.

scholarly journals Research on the Blade Motion of a Bidirectional Energy-Generating Turbine under Integrated Wave and Tidal Current Action

2021 ◽  
Vol 9 (8) ◽  
pp. 869
Author(s):  
Ya-Mei Li ◽  
Ze-Yu Li ◽  
An-Dong Liu ◽  
Yu-Tian Zhu ◽  
Shi-Ming Wang ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Tidal Current ◽  
Flow Direction ◽  
Time Series Prediction ◽  
Tidal Currents ◽  
Current Data ◽  
Wave Direction ◽  
Tidal Current Energy ◽  
Sea Trial ◽  
Tidal Current Velocity

An integrated wave-tidal current power turbine is affected by both wave and tidal current forces, and its energy efficiency is closely related to the velocity and direction of the two forces. To improve the probability of the horizontal axis turbine reaching maximum energy efficiency under real-time changing sea conditions, we performed the following investigations in this study. Based on the actual application scenario of Lianyungang port, a time series prediction model of tidal current (velocity and flow direction) and wave (mean wave direction, mean wave period, and significant wave height) data for the past year was established. The changes in waves and tidal currents within 24 h after the cutoff point of the existing data were predicted. The integrated wave-tidal current mechanism was studied, and the superposition of wave energy and tidal current energy was transformed into the equivalent velocity vector of wave-tidal current integration. The conversion coefficient between waves and equivalent flows was determined by a numerical wave flume simulation. According to the historical wave and tidal current data, the equivalent velocity range of the integrated action of waves and tidal currents in Lianyungang was determined. The influence of different blade motions on the energy harvesting efficiency of the turbine under the corresponding flow conditions was studied using the Computational Fluid Dynamics (CFD) method to determine the blade motion law of the turbine. The blade motion law of the prototype was verified in a sea trial experiment. The experimental results were basically consistent with the simulation results for the blade motion law designed according to the wave and tidal current prediction law. This design scheme can provide a reference for engineering design for the development and utilization of new marine energy.

scholarly journals Australian tidal currents – assessment of a barotropic model (COMPAS v1.3.0 rev6631) with an unstructured grid

2021 ◽  
Author(s):  
David Anthony Griffin ◽  
Mike Herzfeld ◽  
Mark Hemer ◽  
Darren Engwirda
Keyword(s):  
Tidal Current ◽  
Unstructured Grid ◽  
Tide Gauge ◽  
Tidal Currents ◽  
Practical Significance ◽  
Tidal Range ◽  
Validation Dataset ◽  
Validation Data ◽  
Data Set ◽  
Velocity Amplitude

Abstract. While the variations of tidal range are large and fairly well known across Australia (less than 1 m near Perth but more than 14 m in King Sound), the properties of the tidal currents are not. We describe a new regional model of Australian tides and assess it against a validation dataset comprising tidal height and velocity constituents at 615 tide gauge sites and 95 current meter sites. The model is a barotropic implementation of COMPAS, an unstructured-grid primitive-equation model that is forced at the open boundaries by TPXO9v1. The Mean Absolute value of the Error (MAE) of the modelled M2 height amplitude is 8.8 cm, or 12 % of the 73 cm mean observed amplitude. The MAE of phase (10°), however, is significant, so the M2 Mean Magnitude of Vector Error (MMVE, 18.2 cm) is significantly greater. The Root Sum Square over the 8 major constituents is 26 % of the observed amplitude. We conclude that while the model has skill at height in all regions, there is definitely room for improvement (especially at some specific locations). For the M2 major-axis velocity amplitude, the MAE across the 95 current meter sites, where the observed amplitude ranges from 0.1 cm s−1 to 156 cm s−1, is 6.9 cm s−1, or 22 % of the 31.7 cm s−1 observed mean. This nationwide average result is encouraging, but it conceals a very large regional variation. Relative errors of the tidal current amplitudes on the narrow shelves of NSW and Western Australia exceed 100 %, but tidal currents are weak and negligible there compared to non-tidal currents, so the tidal errors are of little practical significance. Looking nation-wide, we show that the model has predictive value for much of the 79 % of Australia’s shelf seas where tides are a major component of the total velocity variability. In descending order this includes the Bass Strait, Kimberley to Arnhem Land and Southern Great Barrier Reef regions. There is limited observational evidence to confirm that the model is also valuable for currents in other regions across northern Australia. We plan to commence publishing ‘unofficial’ tidal current predictions for chosen regions in the near future, based on both our COMPAS model and the validation data set we have assembled.

The Anomaly of Mean Sea Level in Seymour Narrows, B.C.

1954 ◽  
Vol 11 (6) ◽  
pp. 853-883 ◽  
Author(s):  
G. Wilfred LaCroix ◽  
John P. Tully
Keyword(s):  
Sea Level ◽  
Tidal Current ◽  
Hydraulic Head ◽  
Tidal Currents ◽  
Current Data ◽  
Fraser River ◽  
Mean Sea Level

During surveys of the tides and tidal currents in Seymour Narrows (1945 to 1950) the Canadian Hydrographic Service noted that there was a depression of mean sea level of the order of half a foot. There is a considerable fall of sea level along the Narrows and the square of the velocity of the current is proportional to this hydraulic head. The anomaly is a necessary consequence of the velocity, and it can be predicted from either the tidal or the tidal-current data. The annual net transport of water through the Narrows is seaward and is about five times as great as the discharge of the Fraser River.

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