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1.
Numerical simulation of upwelling currents in pockmarks,and data from the Inner Oslofjord,Norway 总被引：5，自引：3，他引：2
The deflection of oceanic or tidal currents into pockmarks has been studied by both general three-dimensional computational
fluid dynamics simulations and acoustic measurements in a number of pockmarks in the Inner Oslofjord, Norway. The modeling
demonstrates upstream convergence of flow lines, followed by upwelling over the pockmark. This upwelling is an effect of deflected
regional currents, not of expulsion of fluids or gas from the seafloor, and is sufficiently strong to prevent the settling
of fine particles. The field measurements, although noisy at low vertical velocities, are consistent with the hypothesis of
upwelling. The reduction in sedimentation rate inferred over the pockmarks (relative to that of the flat surrounding seabed)
can explain the maintenance, or even deepening of pockmarks in the absence of fluid or gas seepage. The current pattern may
also have consequences for the marine biology of pockmarks. 相似文献
2.
Ben Elghali S.E. Balme R. Le Saux K. El Hachemi Benbouzid M. Charpentier J.F. Hauville F. 《Oceanic Engineering, IEEE Journal of》2007,32(4):786-797
This paper deals with the development of a Matlab-Simulink model of a marine current turbine system through the modeling of the resource and the rotor. The simulation model has two purposes: performances and dynamic loads evaluation in different operating conditions and control system development for turbine operation based on pitch and speed control. In this case, it is necessary to find a compromise between the simulation model accuracy and the control-loop computational speed. The blade element momentum (BEM) approach is then used for the turbine modeling. As the developed simulation model is intended to be used as a sizing and site evaluation tool for current turbine installations, it has been applied to evaluate the extractable power from the Raz de Sein (Brittany, France). Indeed, tidal current data from the Raz de Sein are used to run the simulation model over various flow regimes and yield the power capture with time. 相似文献
3.
Three-dimensional hydrodynamic-eutrophication model (HEM-3D): application to Kwang-Yang Bay, Korea 总被引：9，自引：0，他引：9
The purpose of this paper is twofold: to describe the water quality model of Three-Dimensional Hydrodynamic-Eutrophication Model (HEM-3D) and to present an application of HEM-3D to a coastal system in Korea. HEM-3D, listed as a tool for the development of Total Maximum Daily Load by US Environmental Protection Agency, is a general-purpose modeling package for simulation of the flow field, transport, and eutrophication processes throughout the water column and of diagenetic processes in the benthic sediment. This paper describes the water quality model of HEM-3D with emphasis on its unique features. Excessive loadings of organic wastes have significantly deteriorated water quality conditions of Korean coastal waters. This paper presents an application of HEM-3D to Kwang-Yang Bay, a coastal system in Korea, which is one of the first water quality modeling efforts for Korean coastal waters accompanied by a relatively comprehensive field program. The current status of data availability for water quality modeling in Korea is discussed. 相似文献
4.
Avidesh Seenath 《Marine Geodesy》2013,36(6):581-604
AbstractThis article examines whether Digital Elevation Model (DEM) resolution affects the accuracy of predicted coastal inundation extent using LISFLOOD-FP, with application to a sandy coastline in New Jersey. DEMs with resolution ranging from 10 to 100 m were created using coastal elevation data from NOAA, using the North American Vertical Datum of 1988. A two-dimensional hydrodynamic flood model was developed in LISFLOOD-FP using each DEM, all of which were calibrated and validated against an observed 24-h tidal cycle and used to simulate a 1.5 m storm surge. While differences in predicted inundated area from all models were within 1.0%, model performance and computational time worsened and decreased with coarser DEM resolution, respectively. This implied that using a structured grid model for modeling coastal flood vulnerability is based on two trade-offs: high DEM resolution coupled with computational intensity, but higher precision in model predictions, and vice versa. Furthermore, water depth predictions from all DEMs were consistent. Using an integrated numerical modeling and GIS approach, a two-scale modeling strategy, where a coarse DEM is used to predict water levels for projection onto a fine DEM was found to be an effective, and computationally efficient approach for obtaining reliable estimates of coastal inundation extent. 相似文献
5.
A snapshot of suspended sediment and fluid mud occurrence in a mixed-energy embayment, Tijucas Bay, Brazil 总被引：1，自引：1，他引：0
Carlos Augusto Fran ça Schettini Dermeval Costa de Almeida Eduardo Siegle Ant ônio Carlos Brand ão de Alencar 《Geo-Marine Letters》2010,30(1):47-62
Along the southern Brazilian coast, Tijucas Bay is known for its unique muddy tidal flats associated with chenier plains.
Previous field observations pointed to very high suspended sediment concentrations (SSCs) in the inner parts of the bay, and
in the estuary of the Tijucas River, suggesting the presence of fluid mud. In this study, the occurrences of suspended sediments
and fluid mud were examined during a larger-scale, high-resolution 2-day field campaign on 1–2 May 2007, encompassing survey
lines spanning nearly 80 km, 75 water sampling stations for near-bottom density estimates, and ten sediment sampling stations.
Wave refraction modeling provided qualitative wave energy estimates as a function of different incidence directions. The results
show that SSC increases toward the inner bay near the water surface, but seaward near the bottom. This suggests that suspended
sediment is supplied by the local rivers, in particular the Tijucas. Near-surface SSCs were of the order of 50 mg l−1 close to the shore, but exceeded 100 mg l−1 near the bottom in the deeper parts of the bay. Fluid mud thickness and location given by densimetry and echo-sounding agreed
in some places, although being mostly discordant. The best agreement was observed where wave energy was high during the campaign.
The discrepancy between the two methods may be an indication for the existence of fluid mud, which is recorded by one method
but not the other. Agreement is considered to be an indication of fluidization, whereas disagreement indicates more consolidation.
Wave modeling suggests that waves from the ENE and SE are the most effective in supplying energy to the inner bay, which may
induce the liquefaction of mud deposits to form fluid mud. Nearshore mud resuspension and weak horizontal currents result
in sediment-laden offshore flow, which explains the higher SSCs measured in the deeper parts of the bay, besides providing
a mechanism for fine-sediment export to the inner shelf. 相似文献
6.
《Marine Policy》2016
Information on the cost of fishing is integral in measuring fisheries performance and correctly evaluating the economic impacts of fisheries regulations and management rules. However, limited availability of cost data often renders such analyses either incomplete or implausible. This study discusses a survey effort that was undertaken in the Northeast US to collect fisheries annual fixed cost data directly from commercial fishermen. Stratified random samples of fishing vessel owners were surveyed in 2012 and 2013. An overview of the survey procedures, sample selection and administration is given here. The data cleaning process, non-response bias and data summaries are also presented. A modeling framework is discussed for estimating fisheries cost data. Robust cost models in combination with regular data collection efforts will allow for more complete economic and financial analyses relevant to fisheries management and conservation. 相似文献
7.
O. A. Druzhinin V. V. Papko D. A. Sergeev Yu. I. Troitskaya 《Izvestiya Atmospheric and Oceanic Physics》2006,42(5):615-626
The far-wake flow past a sphere towed in a fluid with high Reynolds and Froude numbers and with a pycnocline-form salt-density stratification is studied in a laboratory experiment based on particle image velocimetry and in numerical and theoretical modeling. In the configuration under consideration, the axis of sphere towing is located under a pycnocline. Flow parameters, the profiles of density and average velocity, and the initial field of velocity fluctuation in numerical modeling are specified from the data of the laboratory experiment. The fields of fluid velocity at different times and the time dependences of integral parameters of wake flow, such as the average velocity at the axis and the transverse width of the flow, are obtained. The results of numerical modeling are in good qualitative and quantitative agreement with the data of the laboratory experiment. The results of the laboratory experiment and numerical modeling are compared to the predictions of a quasi-linear and quasi-two-dimensional theoretical model. The time evolution of both the average velocity at the axis and the transverse width of the wake is obtained with the model and is in good agreement with the experimental data. The results of numerical modeling also show that, under the effect of velocity fluctuation in the wake, internal waves whose spatial period is equal to the characteristic period of the wake’s vortex structure are excited efficiently in the pycnocline. 相似文献
8.
Shape optimization of two-dimensional cavitators in supercavitating flows, using NSGA II algorithm 总被引：1，自引：0，他引：1
The reduction of energy consumption of high speed submersible bodies is an important challenge in hydrodynamic researches. In this paper, shape optimization of two-dimensional cavitators in supercavitating flows is studied. A two dimensional supercavitation potential flow passes a symmetric two dimensional cavitator, which is placed perpendicular to the flow in a channel of infinite length and immediately a cavity is formed behind the cavitator. This is because of the generation of a gas or vapor cavity between the body and the surrounding liquid due to the change in a high speed flow direction passing the cavitator. Drag force acting on this supercavitating body dictates the thrust requirements for the propulsion system, to maintain a required cavity at the operating speed. Therefore, any reduction in the drag force, by modifying the shape of the cavitator, will lead to decrease this force. This study concentrates on the optimization of two dimensional cavitators in order to decrease drag coefficient for a specified after body length and velocity in a potential flow. To achieve this goal a multi-objective optimization problem is defined to optimize cavitator shapes in supercavitating flow. The so-called NSGA II (Non-dominated Sorting Genetic Algorithm) algorithm is used as an optimization method. Design parameters and constraints are obtained according to supercavitating flow characteristics and cavitator modeling and objective functions are generated using Linear Regression Method. The obtained results are compared with other classic optimization methods, like the weighted sum method, for validation. 相似文献
9.
《Ocean Modelling》2002,4(3-4):249-267
During the course of developing new numerical algorithms for a terrain-following ocean modeling system (TOMS), different numerical aspects have been evaluated through a comparison between two widely used community ocean models, the Princeton ocean model (POM) and the regional ocean modeling system (ROMS). While both models aim at modeling coastal to basin-scale problems using similar grids, their numerical algorithms, code structure, and parameterization options are very different. Sensitivity studies with an idealized channel flow and a steep seamount configuration demonstrate how different algorithms in the two models may affect numerical errors, the stability of the code and the computational efficiency. For example, new pressure gradient schemes using polynomial fits and new time stepping algorithms may reduce numerical errors and allow using longer time steps than standard schemes do. However, the new schemes may require more careful choices of time steps and the use of higher order advection schemes to maintain numerical stability. 相似文献
10.
The paper analyzes the effect which prescribed errors in the cross-shore boundary conditions for a computational domain along a beach have on the flow field predicted inside the domain. This problem is relevant because errors in boundary conditions are unavoidable when modeling limited domains of a nearshore region. For simplicity, we consider a longshore uniform plane beach with monochromatic, obliquely incident waves, and assume depth uniform currents. It is then studied analytically and numerically how small perturbations of the boundary conditions along both upstream and downstream cross-shore boundaries spread inside the computational domain. It is found that the errors at the upstream cross-shore boundary tend to spread over a long distance downstream of the boundary, while the influence of the errors in the downstream boundary condition is limited to the adjacent upstream area of the computational domain. Both the numerical and analytical solutions show that the errors introduced at the upstream boundary decay exponentially in the surf zone at a rate proportional to the bottom friction. A simple formula is developed to estimate the influence distance of the upstream errors. If we consider the mismatch in the volume flux at the upstream boundary, the error merely redistributes in the cross-shore direction to conserve volume. In the case of excessive flux or velocity specified at the cross-shore boundaries, a circulation cell tends to appear in the offshore region where the errors caused by the boundary mismatch increase with the cross-shore width of the model domain. 相似文献
11.
《Oceanic Engineering, IEEE Journal of》2006,31(2):432-453
Precise control of trawl systems is assumed to be beneficial from both economic and environmental reasons. Using the trawl doors as actuators could increase the amount of available control forces. Adequate mathematical models of the hydrodynamic fores on the trawl doors are needed for control system design and verification. This paper presents a method for mathematical modeling of the hydrodynamic forces on the trawl doors. These forces are divided into steady-state forces and transient effects. The six degrees of freedom (six dof) steady-state hydrodynamic coefficients of a trawl door have been found as a function of its angles of attack and slip, based on wind-tunnel experiments. The coefficients are parameterized for smoothing and computational performance, and methods for extending the validity of the model in terms of orientation and trawl door shape are presented. The transient effects are described as functions of relative accelerations between the trawl door and the ambient water, angular velocities of the trawl door and circulation buildup. These effects are manifestations of variations in the flow around the trawl door and its wake, and a numerical method based on potential theory is employed to investigate them. A computational efficient, nonlinear, state–space model of the hydrodynamic forces is finally proposed. It accounts for steady-state and unsteady hydrodynamic forces and moments in six dof, suitable for trawl control system design and analysis. 相似文献
12.
J.D. Van Wees F. van Bergen P. David M. Nepveu F. Beekman S. Cloetingh D. Bonté 《Marine and Petroleum Geology》2009
Tectonic modeling is often neglected in the basin modeling workflow and heat flow is most times considered a user input. Such heat flows can, therefore, result in erroneous basin modeling outcomes, resulting in false overoptimistic identification of prospective areas or failure to identify prospects. This is particularly true for areas with limited data control such as frontier basin areas, or deep unexplored plays in mature basins. 相似文献
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15.
OBS广角反射地震及其意义 总被引：2，自引：0，他引：2
在蒸发岩、玄武岩等高阻抗岩层发育地区 ,常规反射地震往往难以获取高阻抗层以下的地层地质信息。而使用海底地震仪 ( OBS)进行广角反射地震测量 ,可较好地解决高阻抗层屏蔽问题 ,它是开展海上地质构造勘查的一种行之有效的方法。对 OBS广角反射地震法的原理 ,海上测量方法 ,资料处理 ,时间剖面解释及地下地质构造计算机模拟方法作了阐述 ,对 OBS广角反射地震勘探法的成功范例——苏伊士湾高蒸发岩发育区结晶基底勘探作一扼要介绍。 相似文献
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17.
在海洋流场数值计算中，当流场中建筑物尺度相对平面网格步长太小时，计算中难以引进其作用，在所得计算结果中难以反映其影响。本文依据流量连续、能量守恒规律，通过水力学物模实验，求得建筑物存在情况下的谢才系数Ｃ，解决了计算中的难题。 相似文献
18.
This paper reviews recent progress on modeling cross-frontal water exchange on Georges Bank undertaken as part of the U.S.
Global Ecosystem Northwest Atlantic/Georges Bank Study (U.S. GLOBEC/Georges Bank Program). A simple conceptual model is described
first, followed by a discussion of four physical mechanisms associated with (1) strong nonlinear interaction, (2) asymmetric
tidal mixing, (3) varying wind forcing, and (4) chaotic mixing. Some critical issues in modeling studies of fronts are also
addressed. A new unstructured grid, finite-volume coastal ocean ecosystem model is introduced. This model combines the best
of the finite-difference method for the simplest discrete computational efficiency and the finite-element method for geometric
flexibility. Because the finite-volume method discretizes the integral form of the governing equations, this approach provides
a better representation for the conservation laws of mass and momentum are satisfied, which is particularly important in the
frontal regions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
1 .IntroductionUnder the influence of surface waves ,sandripples often appear on beaches . Whenthe amplitudeof water oscillationis sufficientlylarge ,vortices are formed onthe lee of every sand ripple crest . A-mongthese vortices ,the most important are t… 相似文献
20.
局部海洋地磁场模型可以为水下地磁匹配导航与磁性目标探测等工作提供高精度的海域地磁背景场数据。针对目前区域地磁场模型构建方法中未考虑到高度或深度变化的影响,截断阶数难以确定及存在边界效应等问题。根据海洋磁力测量的特点,顾及磁测点高度数据,引入粒子群优化的最小二乘支持向量机法(PSO-LSSVM)构建局部海洋三维地磁场模型。在仿真与实测数据建模试验中,与Taylor多项式法、BP神经网络法及曲面样条函数法比较,结果表明,无论是在地磁变化平缓区还是复杂区,PSO-LSSVM法的建模精度均是最高的,建议在局部海洋地磁场模型构建中采用。 相似文献