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1.
本文用有限元法配合时步处理来求解三维非线性水波的绕射问题,自由表面条件和物面条件都满足到二阶,采用人工阻尼区来吸收反射波,流场内的速度势通过求解有限元方程得到。对垂直圆柱体的绕射问题进行了计算,得到了自由表面波高时间历程和圆柱所受到的波浪力,计算结果和有关文献的理论计算结果进行了比较。  相似文献   

2.
极限波浪运动特性的非线性数值模拟   总被引:1,自引:0,他引:1       下载免费PDF全文
宁德志  滕斌  姜立明  臧军 《海洋学报》2008,30(3):126-132
利用时域高阶边界元方法建立了模拟极限波浪运动的完全非线性数值模型,其中自由水面满足完全非线性自由水面条件.采用半混合欧拉-拉格朗日方法追踪流体瞬时水面,运用四阶Runge-Kutta方法更新下一时间步的波面和速度势,同时应用镜像格林函数消除水槽两个侧面和底面上的积分.研究中利用波浪聚焦的方法产生极限波浪,并且在水槽中开展了物理模型实验,将测点试验数据与数值结果进行了对比,两者吻合得很好.对极限波浪运动的非线性和流域内速度分布进行了研究.  相似文献   

3.
倪云林  滕斌 《海洋学报》2021,43(10):90-96
本文建立了波浪在局部可渗透水平海床上传播的解析解,并研究了波浪在局部可渗透海床上的透射、反射问题。研究中将计算域划分为4个区域,中间区域为流域,海底可渗透,其下区域为多孔介质海床,左右两个区域也为流域,但海底不可渗透。应用线性波浪理论,建立了各流域包含非传播模态的速度势表达式,给出了海床内部的压强表达式,并利用交界面上匹配条件,求解了表达式中的待定系数。基于该解析模型,探讨了海床渗透系数、相对水深、渗透海床长度对波浪传播变形的影响。结果表明,波高沿程衰减,强度随渗透系数、渗透海床长度的增加以及相对水深的减小而变大;局部可渗透海床会引起波浪的反射和透射,随着海床长度的增加,反射系数振荡变化,并最终趋于常数,透射系数指数衰减,并最终趋于0。  相似文献   

4.
本文基于作者在文献中给出的二阶绕射问题的无穷远场条件及无穷远场解,构造了一个适用于二阶绕射问题的无限元。无限元中沿径向(r方向)的插值与二阶绕射问题的远场高阶渐近解的r方向变化规律相同。本文利用内域有限元与外域无限元协调匹配的方法,在二阶逼近的意义下求解了非线性圆柱体绕射问题,给出了波力与波浪爬高的解。本文求出的由二阶势在物面上积分所表达的二阶力部分与Taylor与Hung用一阶势及一个假想的辐射势在自由表面上积分所表达的对应的二阶力部分完全吻合。本文给出的波力与波浪爬高计算结果分别与Chakrabati的波力实验及Isaacson的波浪爬高实验进行了比较,结果吻合得相当好。  相似文献   

5.
基于高阶边界元的三维数值波浪港池   总被引:9,自引:1,他引:8  
初步建立了一个基于高阶边界元的三维数值波浪港池,港池具有造波和消波功能。采用高阶边界元16节点四边形单元和基于二阶显式泰勒展开的混合欧拉-拉格朗日时间步进求解带自由表面的完全非线性势流方程。模型中对于影响数值精度的问题作了细致的处理。数值计算结果表明本港池可以用来模拟非线性波浪的传播,具有很高的数值精度和稳定性。  相似文献   

6.
本文给出有限水深二维物体二阶绕射势在外域中的解析表达式,从而准确满足二阶绕射势的辐射条件。二阶绕射势在内域自由表面上的边界条件则由一阶势的数值微分求得。然后对内域用简单Green函数法求得二阶绕射势。本文对二维浮体和潜体在不同水深和潜深情况下的绕射问题进行了计算,求得了二阶绕射势和二阶定常及倍频波浪力。讨论了水深和潜深对波浪力的影响以及二阶绕射势对非线性波浪力的贡献  相似文献   

7.
倪云林  龚倩  沈梦佳 《海洋学报》2022,44(9):124-131
与海床不可渗透的情况相比,波浪在可渗透海床上传播时会发生波能衰减。本文将基于可渗透海床上一维修正型缓坡方程,建立方程求解的有限差分模型。将通过与不可渗透海床上矩形Bragg防波堤对波浪反射系数解析解的对比,验证有限差分模型的正确性和适用性。将进一步研究海床可渗透情况下,海床的渗透性参数、坝体的相对宽度、数量、浸没度对波浪反射系数的影响及其与海床不可渗透情况下的差异。本文研究发现,Bragg共振发生时的反射系数随坝体数量的增多而增大,随海床渗透性参数和坝体浸没度的增大而减小,并且存在一个坝体相对宽度值会使Bragg共振反射达到最大。相较于海床不可渗透的情况,发生Bragg共振反射的波浪频率几乎相同,但反射系数减小,而且零反射(或全透射)现象不再存在。  相似文献   

8.
椭圆型缓坡方程的一个有效的有限元解   总被引:7,自引:0,他引:7  
赵明  滕斌 《海洋学报》2002,24(1):117-123
将海绵层消波的方法用于有限元方法中,提出了缓坡方程的一种有效的有限元求解方法.在应用有限元法求解椭圆型缓坡方程时,通过在方程中加摩阻项,并在入射边界(波浪由此边界进入计算域)处使用不连续单元,将绕射势从总势中分离出来,在边界上利用海绵层进行消波处理,有效地消除了由于引用放射边界条件引起的误差和数值反射现象.  相似文献   

9.
三维物体上二阶波浪绕射的实时模拟   总被引:1,自引:1,他引:0  
柏威  滕斌 《海洋工程》2001,19(3):43-50
采用二阶时域理论对非线性波浪在任意三维物体周围的绕射问题进行了研究,对自由表面边界条件进行Taylor级数展开,应用摄动展开可以建立相应的边值问题,而且此边值问题的计算域不随时间变化,运用基于B-样条的边界元方法求解每一时刻的波浪场,二阶自由表面边界条件在时间上进行数值积分,在自由表面加了一个人工阻尼层以避免波浪的反射,速度势分解为已知的入射势和未知的散射势,初始条件采用二阶Stokes波浪场,通过加入物体表面边界条件,得到散射势在时间和空间上的发展,本文对圆柱所受规则波的二阶波浪力和波浪爬高进行了计算,数值结果表明此理论计算准确,效率高,数值稳定。  相似文献   

10.
应用基于势流理论的时域高阶边界元方法,建立一个完全非线性的三维数值波浪水槽,通过实时模拟推板造波运动的方式产生波浪。通过混合欧拉-拉格朗日方法和四阶Runge-Kutta方法更新自由水面和造波板的瞬时位置。利用所建模型分别模拟了有限水深波和浅水波,与试验结果、相关文献结果和浅水理论结果吻合较好,且波浪能够稳定传播。系统地讨论造波板的运动圆频率、振幅和水深等对波浪传播和波浪特性的影响,并对波浪的非线性特性进行分析,研究发现造波板运动频率、运动振幅以及水深均将对波浪形态和波浪非线性产生显著影响。结果为真实水槽造波机的运动控制以及波浪生成试验提供了依据,便于实验室设置更合理的参数来准确模拟不同条件下的波浪。  相似文献   

11.
The wave diffraction and radiation problem is studied numerically by using a higher-order boundary element method. The convergence of the higher-order boundary element method is tested systematically for bodies of different shapes. For the second-order force, particular attention is paid to the contribution of the second-order potential, following the line of Molin's approach. For numerical evaluation, the free surface is divided into three subregions; inner, intermediate and outer ones. In the inner region, the integral is evaluated numerically by using higher-order boundary elements. In the intermediate region, semi-analytic form is constructed with the help of eigen functions. In the outer domain, the analytic solution is available. This subdivision scheme reduces the numerical burden remarkably.  相似文献   

12.
A numerical solution is developed to investigate the generation and propagation of small-amplitude water waves in a semi-infinite rectangular wave basin. The three-dimensional wave field is produced by the prescribed “snake-like” motion of an array of segmented wave generators located along the wall at one end of the tank. The solution technique is based on the boundary element approach and uses an appropriate three-dimensional Green function which explicitly satisfies the tank-wall boundary conditions. The Green function and its derivatives which appear in the integral equation formulation can be shown to be slowly convergent when the source and field points are in close proximity. Therefore, when computing the velocity potentials on the wave generators, the source points are chosen outside the fluid domain, thereby ensuring the rapid convergence of these functions and rendering the integral equations non-singular. Numerical results are shown which illustrate the influence of the various wavemaker and basin parameters on the generated wave field. Finally, the complete wave field produced by the diffraction of oblique waves by a vertical circular cylinder in a basin is presented.  相似文献   

13.
14.
In this study, a new analytical solution for the wave-induced seabed response in a multi-layered poro-elastic seabed is developed. The seabed is treated as a multi-layered porous medium and characterized by Biot’s theory. The displacements of the solid skeleton and the pore pressure are expressed in terms of two scalar potentials and one vector. Then, the Biot’s dynamic equation can be solved using Fourier transformation and reducing to Helmholtz equations. To obtain the general solutions for the multi-layered poro-elastic seabed in the frequency-wave-number domain, the transmission and reflection matrices (TRM) method is used to form the equivalent stiffness. Using the boundary conditions and continuous conditions, the frequency-wave-number domain solutions are obtained. Finally, the time-space domain solutions for the multi-layered poro-elastic seabed are obtained by means of the inverse Fourier transformation with respect to the horizontal coordinate. Based on the new solution, a parametric study is carried out to examine the effects of soil characteristics (number of layers, permeability and shear modulus) and wave characteristics (water depth and wave steepness) on seabed responses. The results indicate that the seabed response is affected significantly by permeability, shear modulus and relative water depth.  相似文献   

15.
波浪作用下海床动力反应的数值分析   总被引:5,自引:3,他引:2  
栾茂田  王栋 《海洋工程》2001,19(4):40-45
近海和离岸建筑物的基通常处于连续不断的小风浪作用之下,可将其变形视为弹性。基于二维广义Biot理论,提出了线性或非线性波浪作用下饱和弹性海床动力应应的时域有限元数值解法。静力平衡条件和Biot方程组成的边值方程可视为其特例,在比较算例中,数值计算得到的孔压和有效应力幅值沿海床深度的分布与解析解十分吻合。土骨架和孔隙流体的加速度对海床动力反应的影响很小。具体算例表明,线性波沿缓坡海床传播时,土层中超静孔压和有效应力幅值随之增大,有可能发生滑动坡坏。所提出的数值解法能够灵活地处理非线性波浪荷载,海底复杂地质条件和波浪沿缓坡传播等复杂情况。  相似文献   

16.
This paper concerns the propagation of transient wave groups, focused at a point in time and space to produce locally large waves having a range of steepness. The experimental study was carried out in a wave flume at Dalian University of Technology. The numerical simulations were based on a nonlinear boundary integral equation solved by a higher-order boundary element method (HOBEM). Rather than simulate the whole experimental tank, local surface elevation measurements were used to drive the numerical solution from a point less than two wavelengths upstream of the focus position, leading to significant savings in computational time. Excellent agreement is achieved between the water surface elevations and the water particle kinematics measured in the experiments and those predicted numerically at wave group focus, even for near-breaking waves up to a steepness of kA=0.405 for which even locally matched 2nd-order theory is inadequate. Results based on the linear and 2nd-order theory are also presented in the comparisons. When compared with the first- and 2nd-order solutions, the fully nonlinear wave–wave interactions produce a steeper wave envelope in which the central wave crest is higher and narrower, while the adjacent wave troughs are broader and less deep.  相似文献   

17.
A higher-order boundary element method (HOBEM) for simulating the fully nonlinear regular wave propagation and diffraction around a fixed vertical circular cylinder is investigated. The domain decomposition method with continuity conditions enforced on the interfaces between the adjacent sub-domains is implemented for reducing the computational cost. By adjusting the algorithm of iterative procedure on the interfaces, four types of coupling strategies are established, that is, Dirchlet/Dirchlet-Neumman/Neumman (D/D-N/N), Dirchlet-Neumman (D-N), Neumman-Dirchlet (N-D) and Mixed Dirchlet-Neumman/Neumman-Dirchlet (Mixed D-N/N-D). Numerical simulations indicate that the domain decomposition methods can provide accurate results compared with that of the single domain method. According to the comparisons of computational efficiency, the D/D-N/N coupling strategy is recommended for the wave propagation problem. As for the wave-body interaction problem, the Mixed D-N/N-D coupling strategy can obtain the highest computational efficiency.  相似文献   

18.
Research on the response of random wave on offshore structures has received great deal of attention of many researchers and engineers in the design of marine structures. Most previous investigations have been limited to the regular waves. In this paper, based on Longuet–Higgins random wave theory and finite element method, a numerical model for random wave-induced seabed response is established. The seabed is treated as poroelastic medium and characterized by Biot’s partly dynamic equations (u–p model). The JONSWAP spectrum is adopted in Longuet–Higgins model, which is based on the cumulative superposition of linear diffraction solution. Based on the numerical results, the effects of random wave on seabed response are investigated by comparing with the corresponding Stokes wave and cnoidal wave. Then, a parametric study is conducted to examine the effect of wave and soil characteristic on the seabed.  相似文献   

19.
精确模拟非线性波沿斜面传播过程非常困难,为此论文从势函数的边界积分方程出发,建立了一种时域内二维波浪模拟的数值模型,主要用来模拟完全非线性波浪的传播变形过程。论文的数值模型使用高阶二维边界元方法,采用可调节时间步长的基于二阶显式泰勒展开的混合欧拉-拉格郎日时间步进来求解带自由表面的线性或完全非线性波浪传播问题。在计算区域一端造出线性或非线性的周期性波浪,另一端采用消除反射波的人工粘性吸收边界。通过与现有理论比较证明了论文数值方法所得结果是准确可靠的。  相似文献   

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