共查询到19条相似文献，搜索用时 234 毫秒
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基于线性势流理论,利用高阶边界元法研究了规则波在三维局部渗透海床上的传播。根据Darcy渗透定律推导出渗透海床的控制方程,利用渗透海床顶部和海底处法向速度和压强连续条件得到渗透海床顶部满足的边界条件。根据绕射理论,利用满足自由水面条件的格林函数建立了求解渗透海床绕射势的边界积分方程,采用高阶边界元方法求解边界积分方程进而得到自由水面的绕射势和波浪在局部渗透海床上传播过程中幅值的变化情况。通过与已发表的波浪对圆柱形暗礁的时域全绕射结果对比,证明了本文建立的频域方法计算波幅的正确性和有效性。利用这一模型研究了三维矩形渗透海床区域上波浪的传播特性,并分析了入射波波长、海床渗透特性系数等参数对波浪传播的影响。 相似文献
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本文主要讨论了含有内部源和非线性边界流耦合的双重退化非线性抛物型方程组解的整体存在和爆破性质,在合理的假设下,通过比较原理得到该方程组的所有正解整体存在的充分必要条件。 相似文献
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沿海国家国内州际(省际、县际或郡际)间海洋边界划定案例至今尚少。据悉,我国国内省际间海洋边界划定工作有的省份目前正在运筹之中。为了配合这一工作的开展,现将所掌握的资料介绍如下,以备有关同志参考。 资料表明,某些国家国内各州海洋边界划定与国际海洋边界划定在理论和方法上大致相 相似文献
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实际工程中存在大量的曲边界,因此在曲边界上的计算准确性可以考察出一个数值模型的实用价值。利用Beji的改进型Boussinesq方程建立了一个有限元方法的数值波浪模型。造波方面采用Fenton提出的非线性规则波浪解;在墙边界处,以求解法线方向和切线方向的速度和导数代替求解x、y方向的速度和导数,从而使边界条件直接适用、严格满足,保证了对曲边界计算的准确性。"重开始广义极小残量法"的使用保证了求解方程组的效率和精度,使造波和边界处理方法的有效性和准确性得到了合理地诠释。通过与试验数据、他人数值结果、解析解的比对,显示出该模型计算稳定、结果准确,真正体现出了有限元方法对曲边界适用的优势。 相似文献
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考虑土骨架加速度效应的海床动力反应及其影响因素分析 总被引：2，自引：0，他引：2
由Biot二维广义动力固结理论的形式基本控制方程出发,忽略孔隙流体的加速度,提出了饱和海床动力反应的时域有限元数值解法.联立静力平衡条件和Biot固结方程的退化法所得到的数值解可视为其特例.在比较算例中,退化法得到的超静孔压和有效应力幅值沿海床深度的分布与解析解一致.一般情况下,土骨架的加速度对海床的有效应力和超静孔压影响很小,控制方程可以退化为Biot理论.成层海床上部的粗砂层不会使超静孔压幅值在海床表面下较浅的深度内迅速衰减,难以改变海床的瞬时循环液化深度. 相似文献
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为有效保护和合理利用广西红树林,探讨了自2000年到2100年全球海平面上升、地壳上升和潮滩沉积对英罗湾红树林分布的影响。采用机理分析方法建立红树林边界位置预测模型;利用预测模型计算在2000年数字高程模型上定位2100年红树林边界的数据;利用Global Mapper软件在2000年数字高程模型上确定红树林边界的位置。利用Mapinfo professional地理信息系统软件分析海平面上升引起的红树林边界的移动。通过研究得到在2000年数字高程模型上表达2100年红树林边界位置的数据,以及自2000年到2100年红树林边界移动专题地图。结果表明:自2000年到2100年,低、中模式海平面上升,英罗湾红树林边界向外扩展,面积增大;高模式海平面上升,红树林边界向陆移动,面积增大;极端模式海平面上升,红树林边界向陆移动,面积减小。 相似文献
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本文研究在圆环区域上带梯度项和完全非线性项的半线性椭圆型方程边值问题径向大解的爆破速率。在证明一些重要极限的基础上,与常微分方程分析法相结合得到了当完全非线性项满足Keller-Osserman条件,梯度项的指数范围分别在0～1和大于2时径向大解的爆破速率及在加强的条件下大解边界行为的第二次影响. 相似文献
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A methodology is presented for the spectral analysis of the echo returns from elastic spheres submerged in a fluid half-space. The influence of a target depth on its resonances as manifested in the scattered field is assessed. Results are expressed in terms of Debye potentials in the fluid and in the solid. The unknown coefficients arising in these potentials are determined by the application of appropriate boundary conditions at the surface of the elastic sphere and at the free boundary of the fluid. These boundary conditions are satisfied exactly through the use of some known transformations of the basic wave functions. As the depth increases, our results degenerate to earlier results for spheres in unbounded media. In spite of the spherical symmetry of the scatterer, the field is found to be azimuthally dependent because of the influence of the plane free-surface of the fluid. The saddle-point method is used in the asymptotic evaluation of certain coefficients which exhibit the influence of depth on the complex eigenfrequencies of the scatterer. We demonstrate that as the sphere's depth increases, the influence of the boundary decreases. The rate of decrease increases as the azimuthal wavenumberm increases. Thus the influence of the boundary is greatest for eitherm = 0 , or at shallow depths, or both. 相似文献
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本文采用变域变分原理,建立了导热几何形状反演问题的变分原理,同时获得了该问题所需满足的边界条件和附加条件.该变分原理能将未知形状的几何变量及控制方程结合在一个变分泛函中,使得数学描述简洁、紧凑,且几何变量及控制方程的求解能耦合地进行.介绍了运用该变分原理并结合有限元方法进行数值计算的方法. 相似文献
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A full time-domain analysis program is developed for the coupled dynamic analysis of offshore structures. For the hydrodynamic loads, a time domain second order method is developed. In this approach, Taylor series expansions are applied to the body surface and free-surface boundary conditions, and the Stokes perturbation procedure is then used to establish the corresponding boundary value problems with time-independent boundaries. A higher-order boundary element method (HOBEM) is developed to calculate the velocity potential of the resulting flow field at each time step. The free-surface boundary condition is satisfied to the second order by fourth order Adams–Bashforth–Moultn method. An artificial damping layer is adopted on the free surface to avoid the wave reflection. The mooring-line/tendon/riser dynamics are based on the rod theory and the finite element method (FEM), with the governing equations described in a global coordinate system. In the coupled dynamic analysis, the motion equation for the hull and dynamic equations for mooring-lines/tendons/risers are solved simultaneously using the Newmark method. The coupled analysis program is applied for a truss Spar motion response simulation. Numerical results including motions and tensions at the top of mooring-lines/risers are presented, and some significant conclusions are derived. 相似文献
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A nonlinear analysis is made for determining the two-dimensional unsteady potential-flow characteristics about a wing subject to wing-in-ground effect (WIG) operating above progressive water waves. The dynamic boundary condition requiring the constant pressure and the kinematic boundary condition prescribing the continuity in the vertical velocity are satisfied on the undisturbed free surface. The boundary conditions imposed on the free surface are linear, but the kinematic boundary condition satisfied on the foil surface is nonlinear. Through the derivation and evaluation of the time-domain Green's functions for two-dimensional singularities above a free surface, the influence of water waves on the lift performance of the two-dimensional WIG is addressed using the discrete vortex method. Furthermore, the roll-up of the wake vorticity is considered. The comparison of present work with other numerical results available in the literature shows the validation of the present approach. 相似文献
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S. V. Muzylev 《Oceanology》2006,46(4):465-471
Edge waves in an ice-covered sea at a straight coast with a sloping beach are analyzed within the linearized theory. Such waves propagate along the coast with an amplitude which exponentially decays offshore. The problem is examined without using the hydrostatic assumption. The seawater is considered to be a homogeneous, inviscid, nonrotating, and incompressible fluid. Ice with a uniform thickness is considered, with constant values of density, cylindrical rigidity, Poisson ratio, and compressive stress in the ice. The normal velocity at the bottom is zero; the linearized kinematic and dynamic boundary conditions are satisfied at the lower surface of the ice. Explicit solutions for the edge flexural-gravity waves and the corresponding dispersion equations are obtained and analyzed. 相似文献
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王莉萍 《中国海洋大学学报(自然科学版)》1999,(4)
讨论了多圆柱区域上边界仅为Ｈｏｌｄｅｒ连续函数时的全纯函数的Ｒｉｅｍ ａｎｎＨｉｌｂｅｒｔ边值问题。借助于多复变函数的理论,给出了上述边值问题可解的充要条件及较完整的解的表达式 相似文献
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To study the Taiwan Strait （TS）, an unusual sea area, the numerical model in marginal seas of China is used to simulate and analyze the tidal wave motion in the strait. The numerical modeling experiments reproduce the amphidromic system of the M2 tide in the south end of the Taiwan strait, and consequently confirm the existence of the degenerate amphidromic system. On this basis, further discussion is conducted on the M2 system and its formation mechanism. It can be concluded that the tidal waves of the TS is consisted of the progressing wave from the north entrance and the degenerate amphidromic system from the south entrance, in which the progressing wave from the north entrance dominates the tidal wave motion in the strait. Except for the convergent effect caused by the landform and boundary, the degenerate amphidromic system produced in the south of the strait is another important factor for the following phenomena： the large tidal range in the middle of the strait, the concentrative zone of co-amplitude and co-phase line in the south of the strait. The degenerate amphidromic system is mainly produced by the incident Pacific Ocean tidal wave from the Luzon strait and the action by the shoreline and landform. The position of the amphidromic point is compelled to move toward southwest until degenerating by the powerful progressing wave from the north entrance. 相似文献
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Clément (2013) derived a second order ordinary differential equation (ODE) satisfied by the free-surface Green function in the frequency domain. Since then, similar ODEs for the gradient of the Green function have been developed. Unfortunately, all these ODEs degenerate at zero frequency. Therefore, it is not possible to initialize the numerical solution of these ODEs from this zero frequency. Alternative methods based on the shifting of the initial condition to frequencies strictly greater than zero have then been developed.The present paper describes an alternative approach to address this issue. It involves a new function which is the solution of a modified ODE which can be solved from the zero frequency.Finally, comparisons with evaluations of the Green function using the classical direct integration method are provided. They show that the new ODE can provide accurate estimates of the Green function. 相似文献