A Coastal Ocean Model of Semi-Implicit Finite Volume Unstructured Grid

A two-dimensional coastal ocean model based on unstructured C-grid is built, in which the momentum equation is discretized on the faces of each cell, and the continuity equation is discretized on the cell. The model is discretized by semi-implicit finite volume method, in that the free surface is semi-implicit and the bottom friction is implicit, thereby removing stability limitations associated with the surface gravity wave and friction. The remaining terms in the momentum equations are discretized explicitly by integral finite volume method and second-order Adams-Bashforth method. Tidal flow in the polar quadrant with known analytic solution is employed to test the proposed model. Finally, the performance of the present model to simulate tidal flow in a geometrically complex domain is examined by simulation of tidal currents in the Pearl River Estuary.

Development of a High-Resolution Coastal Circulation Model for the Ocean Observatory in Lunenburg Bay

An advanced ocean observatory has been established in Lunenburg Bay of Nova Scotia, Canada as part of an interdisciplinary research project of marine environmental prediction. The development of a high-resolution coastal circulation model is one of important components of the observatory. The model horizontal resolution is 60 m and the vertical resolution is about 1 m. The coastal circulation model is used to simulate the semi-diurnal tidal circulation and associated nonlinear dynamics with the M2 forcing specified at the model open boundaries. The model is also used to simulate the storm-induced circulation in the bay during Hurricane Juan in September 2003, with the model forcing to be the combination of tides and remotely generated waves specified at the model open boundaries and wind stress applied at the sea surface. The model results demonstrate strong interactions between the local wind stress, tidal forcing, and remotely generated waves during this period. Comparison of model results with the surface elevation and current observations demonstrates that the coastal circulation model has reasonable skills in simulating the tidal and storm-induced circulation in the bay.

Theoretical Model and Random Simulation for Nonlinear Interaction of Irregular Waves with Vertical Wall

According to the theoretical solutions for the nonlinear three-dimensional gravity surface waves and their interactions with vertical wall previously proposed by the lead author, in this paper an exact second-order random model of the unified wave motion process for nonlinear irregular waves and their interactions with vertical wall in uniform current is formulated, the corresponding theoretical nonlinear spectrum is derived, and the digital simulation model suitable to the use of the FFT (Fast Fourier Transform) algorithm is also given. Simulations of wave surface, wave pressure, total wave pressure and its moment are performed. The probability properties and statistical characteristics of these realizations are tested, which include the verifications of normality for linear process and of non-normality for nonlinear process; the consistencies of the theoretical spectra with simulated ones; the probability properties of apparent characteristics, such as amplitudes, periods, and extremes (maximum and minimum, positive and negative extremes). The statistical analysis and comparisons demonstrate that the proposed theoretical and computing models are realistic and effective, and estimated spectra are in good agreement with the theoretical ones, and the probability properties of the simulated waves are similar to those of the sea waves. At the same time, the simulating computation can be completed rapidly and easily.

Numerical calculation of hydrodynamic characteristics of tidal currents for submarine excavation engineering in coastal area

In coastal areas with complicated flow movement, deposition and scour readily occur in submarine excavation projects. In this study, a smallscale model, with a high resolution in the vertical direction, was used to simulate the tidal current around a submarine excavation project. The finite volume method was used to solve Navier-Stokes equations and the Reynolds stress transport equation, and the entire process of the tidal current was simulated with unstructured meshes, generated in the irregular shape area, and structured meshes, generated in other water areas.The meshes near the bottom and free surface were densified with a minimum layer thickness of 0.05 m. The volume of fluid method was used to track the free surface, the volume fraction of cells on the upstream boundary was obtained from the volume fraction of adjacent cells, and that on the downstream boundary was determined by the water level process. The numerical results agree with the observed data, and some conclusions can be drawn: after the foundation trench excavation, the flow velocity decreases quite a bit through the foundation trench, with reverse flow occurring on the lee slope in the foundation trench; the swirling flow impedes inflow, leading to the occurrence of dammed water above the foundation trench; the turbulent motion is stronger during ebbing than in other tidal stages, the range with the maximum value of turbulent viscosity, occurring on the south side of the foundation trench at maximum ebbing, is greater than those in other tidal stages in a tidal cycle, and the maximum value of Reynolds shear stress occurs on the south side of the foundation trench at maximum ebbing in a tidal cycle. The numerical calculation method shows a strong performance in simulation of the hydrodynamic characteristics of tidal currents in the foundation trench, providing a basis for submarine engineering construction in coastal areas.

An Improved Approach for Interaction of Wave with Floating Spheres and Its Applications

To develop and utilize marine resources in the deep sea, the higher requirements for floating structures, which are operated in marine environment for a long term, have been put forward. Reasonable structure type and accurate force analysis are favorable guarantees to improve the survival performance and working performance of the floating structures. Floating spheres fastened by mooring cable were widely used in floating structures. In this paper, the wave forces of the floating sphere are efficiently and accurately calculated by solving the geometric relationship between the non-submerged floating sphere and wave surface. Combined with the hydrodynamic calculation of mooring cables based on the lumped mass method, the coupled motion model of multi-floating spheres fastened by multi-mooring cable was established under wave action. Furthermore, according to the floating structures fastened by mooring cable in the actual ocean engineering, the topological method of multi-mooring cables fastening the multifloating spheres was expounded from simple to complex. Finally, the modeling method and preliminarily hydrodynamic characteristics of the fastened floating structures, including the mooring system of renewable energy devices, ocean buoy, and coral nursery, were presented and analyzed in detail. The obtained results showed that the method for calculating the wave force on the floating sphere developed in this paper can accurately describe the motion process of the floating mooring sphere and the force on the mooring cable. Also, the topological method of multiple buoys and multiple mooring cables could efficiently establish various numerical hydrodynamic models of fastened buoys in ocean engineering.

Numerical study of current fields near the Changjiang Estuary and impact of Quick-EnKF assimilation

A 30-d current numerical simulation is running for the Yangshan Port,the Changjiang Estuary,the Hangzhou Bay and their adjacent seas using a finite volume coastal ocean model （FVCOM）,with Changjiang River runoff and wind effect being considered.At the open boundary,this model is driven by the water level obtained from prediction including eight main partial tides.After the harmonic analysis,the cotidal chart and the iso-amplitude line as well as the current ellipse distribution map are displayed to illustrate the propagation property of a tidal wave.Horizontal velocity of both the U and V components coincides with the actual measurement,which shows that the model result is credible to describe the hydrodynamic pattern in this sea area.On this basis,real-time current data from high-frequency radar is assimilated with the implementation of quick ensemble Kalman filter,which takes the variation tendency of the state vector to compute the analysis field,instead of integrating the field for N （the number of ensemble） times as it used to in the standard EnKF,aiming at raising the efficiency of computation,reducing the error of prediction and at the same time,improving the forecast effect.

Model-Simulated Coastal Trapped Waves Stimulated by Typhoon in Northwestern South China Sea

In this paper, we apply an unstructured grid coastal ocean model to simulate variations in the sea level and currents forced by two typhoons in the northwestern South China Sea(SCS). The model simulations show distinct differences for the two cases in which the typhoon paths were north and south of the Qiongzhou(QZ) Strait. In both cases, coastal trapped waves(CTWs) are stimulated but their propagation behaviors differ. Model sensitivity simulations suggest the dominant role played by alongshore wind in the eastern SCS(near Shanwei) and southeast of Hainan Island. We also examine the influence of the Leizhou Peninsula by changing the coastline in simulation experiments. Based on our results, we can draw the following conclusions: 1) The CTWs stimulated by the northern typhoon are stronger than the southern CTW. 2) In the two cases, the directions of the current structures of the QZ cross-transect are reversed. The strongest flow cores are both located in the middle-upper area of the strait and the results of our empirical orthogonal function analysis show that the vertical structure is highly barotropic. 3) The simulated CTWs divide into two branches in the QZ Strait for the northern typhoon, and an island trapped wave(ITW) around Hainan Island for the southern typhoon. 4) The Leizhou Peninsula plays a significant role in the distribution of the kinetic energy flux between the two CTW branches. In the presence of the Leizhou Peninsula, the QZ branch has only 39.7 percent of the total energy, whereas that ratio increases to 72.2 percent in its absence.

Probabilistic Approach of Coastal Defense Against Typhoon Attacks for Nuclear Power Plant

With the global warming and sea level rising, it is widely recognized that there is an increasing tendency of typhoon occurrence frequency and intensity. The defenses code against typhoon attacks for nuclear power plant should be calibrated because of the increasing threat of typhoon disaster and severe consequences. This paper discusses the probabilistic approach of definitions about ＂probable maximum typhoon＂ and ＂probable maximum storm surge＂ in nuclear safety regulations of China and has made some design code calibrations by use of a newly proposed Double Layer Nested Mtdti-objective Probability Model （DLNMPM）.

Water Contamination Modeling—A Review of the State of the Science

This paper reports on the current state of surface water and ocean contamination models—based on the needs of US Government agencies, their Information Technology (IT) systems, and business processes. In addition, down-selection and evaluation criteria were applied in a two-step process. In Step 1, sixty five surface water and ocean models were identified and researched. In Step 2, the following criteria were explored for each model: 1) model environment (river, lake estuary, coastal ocean and watershed);2) degree of analysis (screening model intermediate model, advanced model);3) availability (public domain, proprietary);4) temporal variability (steady state or time variable/dynamic);5) spatial resolution (one, two or three dimensional);6) processes (flow, transport, both flow and transport in an integrated system);7) water quality (chemical, biological, radionuclides, sediment);and 8) support (user support/training available, user manuals/documents available).

Investigation and numerical simulation of summer sedimentation in Jiaozhou Bay, China

In recent years,development activities have had a significant impact on the environment of the Jiaozhou Bay,China.To ensure the sustainable economic and social development of the Jiaozhou Bay area,it is necessary to strengthen corresponding control measures.The important prerequisite is to properly understand the environmental conditions laws of natural change,especially the dynamic processes of sediment and the characteristics of landform evolution.Based on the data of continuous observation at 6 stations in Jiaozhou Bay for 25 hours,the Hydrodynamic Eutrophication Model(HEM-3D)was used to simulate the sediment erosion and deposition.The results show that the maximum suspended sediment concentration in the sea area of Jiaozhou Bay is about 40 mg/L,which appears in the northwestern area of the bay top and the Cangkou watercourse area,and the low concentration is located in the area of the central Jiaozhou Bay towards the bay mouth.The suspended sediment is 6?10 mg/L.Affected by a decrease in seawater material,the direction of the prevailing current in the Jiaozhou Bay area is different from that of the sediment transport.The velocity of the flood current is higher than that of the ebb current.However,during flood tide,the flux of resuspended seafloor sediment outside and at the mouth of the bay is limited and cannot contribute significantly to the suspended sediment in the bay.During ebb tide,the resuspended sediment at the shallow-water bay head and the east and west sides spreads toward the bay mouth with the ebb current,although it extends beyond the bay through the bay mouth.The research results can provide scientific support for the Jiaozhou Bay project construction and environmental protection.

Numerical investigation of wave propagation in the Liverpool Bay,NW England

The computer model for near shore wave propagation,SWAN,was used to study wave climates in Liverpool Bay,northwest England with various input parameters,including bottom friction factor,white capping,wind drag formulation and effects of tidal modulations.Results were compared with in-situ measurements and reveal the impacts from these inputs on the predictions of wave height and propagation distributions.In particular,the model results were found very sensitive to different input formulations,and tend to underestimate the wave parameters under storm conditions in comparison with the observations.It is therefore important to further validate the model against detailed field measurements,particularly under large storms that are often of the primary concern.

PREDICTION OF OCEANIC DATA

The Kalman filter is used to predict the velocity of littoral current, the wave direction, the sea depth and the wave steepness. In this paper the Kazumasa model has been modified to deal with two cases: 1) For the positions a bit far from the shore, the interaction between the velocity of littoral current as well as the wave direction and the sea depth as well as the wave steepness must be considered. 2) For the positions very close to the shore, three new parameters describing the asymmetry wave are introduced to deal with wave breaking. The results from the modified model are compared with observed data, and the comparison indicates that the modified model is better and capable of giving more accurate results.

2023年探矿工程十大新闻

1我国第一口万米深地科探井开钻2023年5月30日,我国第一口万米科探井——深地塔科1井在新疆塔里木盆地开钻。这标志着我国向地球深部探测技术系列取得新的重大突破,钻探能力开启“万米时代”,将为我国未来的科学研究和油气资源开发提供重要的基础和支持。

海景路护岸工程波浪数值模拟分析

为解决海岸护岸工程不同重现期的设计波要素计算问题,以荣成市好运角旅游度假区海景路护岸工程为研究对象,根据成山头海洋站数据风、浪资料,结合ECMWF(欧洲中长期天气预报中心)后报长期风、浪资料,采用第三代海浪模式SWAN模型计算得到拟建护岸设计波浪要素,并对结果进行统计分析。结果表明,工程海域各点位的波况受深水重现期波高影响,重现期越长的波浪对工程海域各点位影响越大;防波堤的建设主要受到E、SE、S向波浪影响;工程点波况受水位影响较大。

Mapping sea surface velocities in the Changjiang coastal zone with advanced synthetic aperture radar

Range Doppler velocities derived from the Envisat advanced synthetic aperture radar（ASAR） wide swath images are analyzed and assessed against the numerically simulated surface current fields derived from the finite volume coastal ocean model（FVCOM） for the Changjiang Estuary. Comparisons with the FVCOM simulations show that the European Space Agency（ESA） Envisat ASAR based Doppler shift anomaly retrievals have the capability to capture quantitative information of the surface currents in the Changjiang Estuary. The uncertainty analysis of the ASAR range Doppler velocity estimates are discussed with regard to the azimuthal and range bias corrections, radar incidence angles, inaccuracy in the wind field corrections and the presence of rain cells.The corrected range Doppler velocities for the Changjiang Estuary area are highly valuable as they exhibit quantitative expressions related to the multiscale upper layer dynamics and surface current variability around the East China Sea, including the Changjiang Estuary.

Numerical modeling of the seasonal circulation in the coastal ocean of the Northern South China Sea

The Finite Volume Community Ocean Model(FVCOM)was adapted to the Northern South China Sea(NSCS)to investigate the seasonality of coastal circulation,as well as along-shelf and cross-shelf transport.In fall and winter,southwestward current dominates the NSCS shelf,while the currenfs direction shifts to northeast in summer.The circulation pattern in spring is more complicated:both southwestward and northeastward currents are detected on the NSCS shelf.The mean shelf circulation pattern in winter does not show the permanent counter-wind South China Sea Warm Current(SCSWC)along the 100-200 m isobaths.Meanwhile,the model results indicate a northeastward current flowing along 50-100 m isobaths in spring.Southwestward along-shelf transport varies from 0.30-1.93 Sv in fall and winter,and it redirects to northeast in summer ranging jfrom 0.44—1.09 Sv.Onshore transport is mainly through the shelf break segment southeast of the Pearl River Estuary.

Geomorphology visualization modeling and tidal current virtual reality for coastal ocean

The new technology of geomorphology visualization modeling and virtual reality for tidal current numerical simulation are the important methods utilized in coastal ocean research. In the project of studying the evolutionary trend of radial sand ridges in South Yellow Sea of China, this method becomes the key to reveal the correlation betweenthe seabed topography and the hydrodynamic factor——tidal current. It is proved that using the geomorphology visualization and tidal virtual reality techniques, oceanog-raphers might be able to intuitively discover the interaction pattern of sand ridges and tidal current, predicting the development of sand ridge stability in the future. Furthermore,a prototypic software system——VROcean was designed andimplemented to examine the performance of the new visualization technology on the contrast to traditional methods.

GEOSENSING SYSTEMS ENGINEERING FOR OCEAN SECURITY AND SUSTAINABLE COASTAL ZONE MANAGEMENT

Three major threats to ocean security and coastal zone sustainability - global warming, the loss of ocean biodiversity, and pollution - are combining to threaten the ecological integrity of our marine environment and life support systems. We put forward a geomatics-based systems engineering architecture to identify the location and extent of oil spills, thereby improving the ecological integrity of the world＇s oceans and helping contingency planners to determine required assets, personnel and other resources. This real-time, event-based and cost effective emergency management decision support system can aid in the classification, detection, and monitoring of oil spills in the marine environment. The developed Synthetic-Aperture Radar （SAR） processing and calibration techniques efficiently monitor environmental changes in inaccessible ocean regions, characterize oil spill scenarios, and help to identify spill sources. The system is used to improve emergency management in the Gulf of Mexico, with application to oil spills arising from Hurricane Katrina.

Structural Analysis of Platforms with the Effect of Joint Flexibility

A modified space beam element is presented in this paper to consider the local joint flexibility of T, Y tubular joints subjected to axial forces and in-plane bending moments for analysis of platforms. Two numerical examples are shown to verify the efficiency and validity of the method presented here.

Recovery Behavior of the Propagating Buckle on Elastic Structures

Based on the beam system model used by Chater, Hutchinson and Neale (1982), the recovery behavior of propagating buckle on elastic structures is first found out from the computational results. As the representative of some elastic structures, the Chater-Hutchinson-Neale model indicates that once the buckle meets arrestors, unlike the case in submarine pipelines, it will be reflected back to continue its propagation in a negative phase or a negative direction. The pressure which maintains the negative propagation, however, is as same as that required for the positive propagation. This fact has been examined in the experiment of the bulge propagation on a long elastic latex tube. The present discovery greatly supports the hypothesis that the buckle propagation corresponds to the coexisting phase of structures.