共查询到20条相似文献，搜索用时 375 毫秒
1.
将伴随同化方法用于渤、黄海NPZD三维浮游生态动力学模型的研究中,利用1998年～2006年的SeaWiFS叶绿素资料作为观测数据进行同化实验,优化难以确定的生态参数.文中对参数在整个计算区域取常数时进行了优化,同时尝试了一种新的参数化方案,即在海区中选取一些点作为独立参数点,其它点的参数由独立参数点的值经过线性插值得到,优化独立点的参数后得到所有计算格点的参数.针对这两种不同的参数化方案做了一系列对比实验,结果表明利用伴随同化方法反演空间分布的参数能有效地提高数值模拟的精度. 相似文献
2.
3.
Chezy型和广义Manning型摩擦关系在渤、黄、东海陆架潮汐模拟中的应用 总被引：1，自引：0，他引：1
以往对渤、黄、东海潮汐数值模拟中使用的摩擦系数大都采用不随地点变化的常数,即采用Chezy型摩擦。为了改善模拟效果,本文比较了Chezy型和广义Manning型摩擦关系,并选择与实测数据符合最好的参数,即最优参数。结果表明,采用广义Manning型摩擦系数所得结果更好。底摩擦系数在0.0009至0.0014之间,显著低于Proudman(1953)给出的0.0026,也比以往大多数已发表的值小。与原始的Manning公式不同(该公式的幂值为负数),本研究得到的幂值为正,表明在渤、黄、东海陆架区。总体上,水体越浅摩擦系数越小。本文给出了根据最优Manning型摩擦参数模拟得出的同潮图和能通量分布图,并描述了它们的特征。 相似文献
4.
渤、黄、东海潮汐开边界的1种反演方法 总被引：7，自引：0，他引：7
潮汐潮流数值模拟中的 1个主要难点在于开边界条件的确定。本文采用伴随方法 ,利用渤、黄、东海的 64个验潮站资料 (潮汐调和常数 ) ,通过反演渤、黄、东海的开边界条件 ,来实现渤、黄、东海 M2 潮波的数值模拟。为了取得较好的数值模拟结果 ,同时对给定的底摩擦系数进行校正 ,计算出调和常数的模拟值与实测值之差的绝对平均值 :振幅差为 4 .0 cm,迟角差为 2 .5°。实验结果较好地体现了渤、黄、东海 M2 潮波的特征。 相似文献
5.
黄海、渤海TOPEX/Poseidon高度计资料潮汐伴随同化 总被引：1，自引：0，他引：1
首先将大约10a的TOPEX/Poseidon(T/P)高度计资料沿星下轨迹点做潮汐调和分析,提取得到各分潮的调和常数,利用伴随同化方法,同化到二维非线性潮汐数值模式中,模拟了黄海、渤海区域M2,S2,O1,K1等4个潮汐分潮,并根据计算结果给出了各分潮的同潮图.将计算值与观测值的进行偏差统计,结果表明计算值与验潮站资料符合良好.研究过程中做了两类试验:一类试验是针对不同的参数进行优化,一类试验是针对不同的资料进行同化.第一类试验表明:将开边界条件和底摩擦系数同时作为模型优化的控制参数,其结果明显优于单独优化开边界条件;第二类试验表明:同时同化高度计资料与验潮站资料,比单独同化其中任一种资料,对模式计算结果都有较好的改进.研究结果表明,采用伴随同化方法,利用T/P高度计资料和验潮站资料作为同化数据能有效改进模拟结果,用来反演黄海、渤海的潮波系统是可行的. 相似文献
6.
吴巍 《中国海洋大学学报(自然科学版)》1995,(3)
采用二维非线性或线性潮波微分方程和三种不同底摩擦形式，在考虑岛屿或忽略岛屿（线性平滑）两种情况下，分别对渤海单个Ｍ２、Ｓ２、Ｋ１、Ｏ１分潮进行了数值计算。得出了这４个分潮在不同情况下的同期时线和等振幅线图及在部分站位上的调和常数值。计算表明，对渤海Ｍ２、Ｓ２、Ｋ１、Ｏ１单个分潮进行数值计算时，非线性方程中浅水和对流非线性项存在或不存在，对计算结果几乎没有影响，亚网格尺度岛屿对计算结果的影响并不大。用实测资料检验并与已有研究结果比较得出：由于水深过浅，底摩擦形式取非线性比取线性好；忽略尺度比网格尺度小得多的岛屿所得结果更合理，计算也更方便。 相似文献
7.
建立南海潮波模式及其伴随同化模式,在传统二维潮波方程的基础上加入了内潮耗散项,考虑了内潮耗散对南海潮波系统的影响,在前人工作基础上,改进了内潮耗散参数化方案,并给出内潮耗散项中地形效应参数的计算公式;通过对比,本文的参数化方案比前人参数化方案能取得更为合理的模拟结果。以63个验潮站和24个TOPEX/Poseidon卫星高度计轨道交叉点处的调和常数作为观测值,利用伴随同化方法来优化模式中的底摩擦系数和内潮耗散系数。为了寻求最优的优化方案,设计了7组数值实验。实验结果表明,实验7先优化内潮耗散系数再优化底摩擦系数的模拟结果最优。利用实验7的模拟结果分析了南海M2分潮的潮波特征,与前人结果基本一致。 相似文献
8.
南海西南部海域M2潮波传播分布研究 总被引：2，自引：0，他引：2
本文使用ADI方法对南海西南海域M2分潮波进行了数值模拟,取得了满意的结果,同时还对此海区的岸形、底形和科氏效应做了数值试验。笔者得出结论:在此海区中存在三个无潮点和三个明显的潮波腹点;泰国湾口的顺时针旋转潮波系统是在弱科氏力作用下,潮波在湾口作缓慢的右转弯形成的;在潮波腹点附近,以腹点为中心流场呈放射状分布。 相似文献
9.
《中国海洋大学学报(自然科学版)》2010,(Z1)
本文基于有限体积方法的海洋数值模式FVCOM,对渤、黄海M2分潮潮汐、潮流进行数值模拟。模式水平采用不规则三角形网格,较好地拟合曲折岸线并提高近岸海域的网格分辨率;底摩擦采用数值模式同化结果,较真实的反应了海底实际底摩擦状况;采用干/湿处理模块,可以较好模拟近岸的潮汐潮流。通过沿岸19个验潮站M2分潮潮汐调和常数的实测值与计算值的对比,振幅平均误差为5.6 cm,位相平均误差为6.1(°),模拟值与实测值较为接近。表层潮流椭圆的分布,基本反映了渤海及黄海北部的潮流特征。 相似文献
10.
11.
I~IOXdifferent tabes of submerged structures restricting wave development are extensively appliedin coastal and barber engineering. Generally speaking, the submerged structures are classified intothree types (see Fig. 1 ): a submerged horizontal plate (fixed submerged structure), a submergedbreakwater (rectangular or trapezoidal) and a step-take structure (toPOgraphy). In order to get aclear understanding of the characteristics of wave motion around submemed structures, manyFig. 1. Fol'InS… 相似文献
12.
13.
This paper introduces a new method to estimate the long-term regional hurricane wind and storm surge hazard. The output is a relatively small set of hurricane scenarios that together represent the regional hazard. For each scenario, the method produces a hazard-consistent annual occurrence probability, and wind speeds and surge levels throughout the study area. These scenarios can be used for subsequent evacuation or loss estimation modeling. This optimization-based probabilistic scenario (OPS) method involves first simulating tens of thousands of candidate hurricane scenarios with wind speeds and approximate surge depths. A mixed-integer linear optimization is then used to select a subset of scenarios and assign hazard-consistent annual occurrence probabilities to each. Finally, a surge model is used to estimate accurate surge depths for the reduced set of events. The method considers the correlation between winds and surge depths and the spatial correlations of each; it is computationally efficient; and it makes explicit the tradeoff between the number of scenarios selected and the errors introduced by using a reduced set of events. A case study for Eastern North Carolina is presented in which a final set of 97 hurricanes provides unbiased results with errors small enough for many practical uses. 相似文献
14.
The vertical mode method in the problems of flexural-gravity waves diffracted by a vertical cylinder
The linear three-dimensional problem of ice loads acting on a vertical circular cylinder frozen in an ice cover of infinite extent is studied. The loads are caused by an uni-directional hydroelastic wave propagating in the ice cover towards the cylinder mounted to the see bottom in water of constant depth. There are no open water surfaces in this problem. The deflection of the ice cover is described by the Bernoulli–Euler equation of a thin elastic plate of constant thickness. At the contact line between the ice cover and the surface of the cylinder, some edge conditions are imposed. In this study, the edge of the ice plate is either clamped to the cylinder or has no contact with the cylinder surface, with the plate edge being free of stresses and shear forces. The water is of finite constant depth, inviscid and incompressible. The problem is solved by both the vertical mode method and using the Weber integral transform in the radial coordinate. Each vertical mode corresponds to a root of the dispersion relation for flexural-gravity waves. It is proved that these two solutions are identical for the clamped edge conditions. This result is non-trivial because the vertical modes are non-orthogonal in a standard sense, they are linearly dependent, the roots of the dispersion relation can be double and even triple, and the set of the modes could be incomplete. A general solution of the wave-cylinder interaction problem is derived by the method of vertical modes and applied to different edge conditions on the contact line. There are three conditions of solvability in this problem. It is shown that these conditions are satisfied for any parameters of the problem. 相似文献
15.
An analytical method is developed to study the sheltering effects on arc-shaped floating perforated breakwaters. In the process of analysis, the floating breakwater is assumed to be rigid, thin, vertical, and immovable and located in water with constant depth. The fluid domain is divided into two regions by imaginary interface. The velocity potential in each region is expanded by eigenfunction in the context of linear theory. By satisfying continuity of pressure and normal velocity across the imaginary fluid interface, a set of linear algebraic equations can be obtained to determine the unknown coefficients for eigenfunction expansions. The accuracy of the present model was verified by a comparison with existing results for the case of arc-shaped floating breakwater. Numerical results, in the form of contour maps of the non-dimensional wave amplitude around the breakwater and diffracted wave amplitude at typical sections, are presented for a range of wave and breakwater parameters. Results show that the sheltering effects on the arc-shaped floating perforated breakwater are closely related to the incident wavelength, the draft and the porosity of the breakwater. 相似文献
16.
Teng Bin Li Yucheng
Associate Professor Dept. of Civil Engineering Dalian University of Technology Dalian Professor Dept. of Civil Engineering Dalian University of Technology Dalian 《中国海洋工程》1996,(3)
- For the discretization of higher order elements, this paper presents a modified integral domain method to remove the irregular frequencies inherited in the integral equation of wave diffraction and radiation from a surface-piercing body. The set of over-determined linear equations obtained from the method is modified into a normal set of linear equations by superposing a set of linear equations with zero solutions. Numerical experiments have also been carried out to find the optimum choice of the size of the auxiliary domain and the discretization on it. 相似文献
17.
Sloshing, or liquid free surface oscillation, in containers has many important applications in a variety of engineering fields. The modal method can be used to solve linear sloshing problems and is the most efficient reduced order method that has been used during the previous decade. In the present article, the modal method is used to solve a nonlinear sloshing problem. The method is based on a potential flow solution that implements a two-phase analysis on sloshing in a rectangular container. According to this method, the solution to the mass conservation equation, with a nonpenetration condition at the tank walls, results in velocity potential expansion; this is similar to the mode shapes used in modal method. The kinematic and dynamic boundary conditions create a set of two-space-dimensional differential equations with respect to time. The numerical solution of this set of differential equations, in the time domain, predicts the time response of interfacial oscillations. Modal method solutions for the time response of container sloshing due to lateral harmonic oscillations show a good agreement with experimental and numerical results reported in the literature. 相似文献
18.
19.
A set of Boussinesq-type equations with improved linear frequency dispersion in deeper water is solved numerically using a fourth order accurate predictor-corrector method. The model can be used to simulate the evolution of relatively long, weakly nonlinear waves in water of constant or variable depth provided the bed slope is of the same order of magnitude as the frequency dispersion parameter. By performing a linearized stability analysis, the phase and amplitude portraits of the numerical schemes are quantified, providing important information on practical grid resolutions in time and space. In contrast to previous models of the same kind, the incident wave field is generated inside the fluid domain by considering the scattered wave field in one part of the fluid domain and the total wave field in the other. Consequently, waves leaving the fluid domain are absorbed almost perfectly in the boundary regions by employment of damping terms in the mass and momentum equations. Additionally, the form of the incident regular wave field is computed by a Fourier approximation method which satisfies the governing equations accurately in water of constant depth. Since the Fourier approximation method requires an Eulerian mean current below wave trough level or a net mass transport velocity to be specified, the method can be used to study the interaction of waves and currents in closed as well as open basins. Several computational examples are given. These illustrate the potential of the wave generation method and the capability of the developed model. 相似文献
20.
《Ocean Engineering》1999,26(4):287-323
A set of Boussinesq-type equations with improved linear frequency dispersion in deeper water is solved numerically using a fourth order accurate predictor-corrector method. The model can be used to simulate the evolution of relatively long, weakly nonlinear waves in water of constant or variable depth provided the bed slope is of the same order of magnitude as the frequency dispersion parameter. By performing a linearized stability analysis, the phase and amplitude portraits of the numerical schemes are quantified, providing important information on practical grid resolutions in time and space. In contrast to previous models of the same kind, the incident wave field is generated inside the fluid domain by considering the scattered wave field in one part of the fluid domain and the total wave field in the other. Consequently, waves leaving the fluid domain are absorbed almost perfectly in the boundary regions by employment of damping terms in the mass and momentum equations. Additionally, the form of the incident regular wave field is computed by a Fourier approximation method which satisfies the governing equations accurately in water of constant depth. Since the Fourier approximation method requires an Eulerian mean current below wave trough level or a net mass transport velocity to be specified, the method can be used to study the interaction of waves and currents in closed as well as open basins. Several computational examples are given. These illustrate the potential of the wave generation method and the capability of the developed model. 相似文献