共查询到20条相似文献，搜索用时 144 毫秒
1.
用一维水力学方程求取泻湖水位及潮汐汊道断面流速——以海南陵水新村港为例 总被引：3，自引：0，他引：3
本文通过一维水力学运动方程及连续性方程,得出一个反映泻湖水位变化的二阶非线性有阻尼的强迫振动方程,采用龙格-库特四步格式进行求解,并以海南陵水新村港为例,计算了泻湖水位及潮汐汊道的断面流速.研究结果表明:(1)一维水力学方程可容易地求得泻湖-潮汐汊道体系中泻湖内的水位及汊道的断面流速,计算简单快捷.(2)一维水力学方程可分析潮汐汊道体系中的一些基本现象.如潮汐汊道对潮波的"过滤器"特征;由于泻湖-潮汐汊道体系的阻尼系数较大所导致的潮波自外向泻湖传播时衰减剧烈;径流对泻湖水位及汊道流速产生有利于落潮优势的影响;风可使泻湖水位抬升或下降等.(3)无论是否考虑泻湖与潮汐汊道面积随水位的变化,一维水力学方程都具有相当大的缺陷.由于其不能反映泻湖内地形的空间变化,也不能解决漫滩与归槽等过程,在外海潮波无次生波的情况下,它本身不能产生次生潮波,因而不能正确地反映潮汐汊道体系的涨落潮历时与流速不对称,从而不能分析泥沙的净输运及潮汐汊道的稳定性问题.(4)新村港泻湖-潮汐汊道体系中潮汐汊道的断面面积大小对整个体系的稳定性及演变趋势起着控制作用. 相似文献
2.
3.
海底输油管线是海洋油气田开发的生命线工程,在复杂的海洋环境中易发生破坏.为使管线实现自埋防护,提出用柔性材料代替刚性导流板安装在管线顶部,不仅可以增加阻水面积,加大冲刷深度和范围,而且可以减缓刚性导流板对管线上部水流的扰动强度和尾流涡旋的扰动强度,减小管线的振动.利用力学关系由变形方程推导出海底管线与海底间距离为零以及不为零情况下柔性导流板变形的二次曲面方程和自由端最大挠度.在单向流条件下将不同材料不同长度的柔性导流板安装在管线中轴上方开展试验研究,测量柔性导流板在水流作用下的变形曲面.对比分析利用公式计算柔性导流板的自由端最大挠度和曲面变形数据与试验结果,发现两者吻合较好. 相似文献
4.
建立了波浪与大孔隙多孔介质相互作用的耦合数学模型,波浪域的控制方程为雷诺时均方程和k-ε紊流模型。对于计算域的入射波采用推板式造波,它可以是线性波、椭圆余弦波和孤立波。采用PLIC-VOF法追踪波浪自由表面。对于多孔介质内的孔隙流场采用非线性Forchheimer方程,两区域共享连续方程,最后导出的波浪域与孔隙流域的压力修正方程具有完全相同的形式,利用这个方程能够同时而不是分别求解波浪场和孔隙流场,避免了在内部边界上给定匹配条件,实现了波浪场与孔隙流场的同步耦合。波浪与粗颗粒海床、平底床面上抛石潜堤及斜坡上抛石潜堤相互作用的验证计算结果表明该模型可用于研究波浪与大孔隙多孔介质相互作用的问题。 相似文献
5.
6.
7.
实际地下储层是含流体的双相介质,常规的弹性波叠前逆时偏移多基于单相介质理论,不能充分考虑地层中的双相介质对地震波场的影响。为研究双相介质中地震波传播对逆时偏移结果的影响,基于Biot的双相介质理论实现了一阶速度-应力双相介质方程的逆时偏移,并基于CUDA实现了双相介质方程逆时偏移的GPU加速。模型实验结果表明,在含流体的双相介质中,双相介质方程逆时偏移的结果比弹性波方程和声波方程的结果更接近真实的构造形态,同时与基于CPU的双相介质逆时偏移相比,基于GPU的逆时偏移可达到27倍的加速比。因此基于GPU加速的双相介质逆时偏移不仅能够实现对双相介质地层的精确偏移成像,而且能够有效提高逆时偏移的计算效率。 相似文献
8.
非线性波浪波面追踪的一种新模式 总被引：1，自引：0，他引：1
基于Laplace方程的Green积分表达式和波面BemouUi方程所建立的非线性波动数学模型,是一个时域上具有初始值的边值问题,而精确地追踪自由表面的波动位置,给出波面运动瞬时的波面高度和波面势函数,是建立时域内非线性波浪数值模式的基础。本文采用0-1混合型边界元剖分计算域边界并离散Laplace方程的Green积分表达式,采用有限元剖分自由水面并推导满足自由表面非线性边界条件的波面有限元方程,联立计算域内以节点波势函数和波面位置高度的时间增量为未知量的线性方程组,通过时步内的循环迭代,给出每个时步上的波面位置和波面势函数,从而建立了一种新的非线性波浪波面追踪模式。数值造波水槽内的波浪试验表明,其数值模拟结果具有良好的计算精度。 相似文献
9.
受到海底、自由表面等强反射界面的影响, 在海底电缆采集的地震资料中鬼波干扰往往非常发育, 在频谱中表现为明显的陷频现象, 严重影响地震剖面的质量, 给后期的处理解释带来困难。为克服这一困难, 根据海底电缆双检(陆检和水检)对下行波场的不同响应, 在深入研究伪多道匹配滤波技术的基础上提出了伪多道双检合成方法。与传统的求取反射系数的双检合成方法不同, 该方法完全数据驱动。在合成数据和渤海地震资料的实际应用中, 鬼波成分得到了明显的压制, 同时拓宽频带, 补偿陷频, 证明了该方法的有效性。 相似文献
10.
11.
The wave dispersion equation has played a very important role in the development of ocean surface wave theories. The evaluation of the length of a water wave is an essential example of solving the dispersion relation. Conventional ocean wave theories have been based on an assumption of a rigid impermeable seabed. Thus, the conventional wave dispersion equation can only be used in the case of a wave propagating over a rigid impermeable seabed. For waves propagating over a porous seabed (such as a sandy bed), the conventional dispersion relation is no longer valid because of the absence of the characteristics of the porous seabed. The objective of this study is to establish a new wave dispersion equation for waves propagating over a porous seabed. Based on the new relation, the effects of a porous seabed on wave characteristics (such as the wavelength and wave profile) are discussed in detail. 相似文献
12.
Tokuo Yamamoto 《Marine Georesources & Geotechnology》2013,31(2):93-130
Abstract The problem of forced vibration of a slightly inelastic porous bed by water waves is treated analytically on the basis of a linearized expression of the nonlinear damping term for the grain‐to‐grain friction in bed soils and the linear theory by Biot (1962a [Jour. Appl. Physics, 33:1482–1498]) on the elastic wave propagation in porous media. A dispersion relation of water waves is obtained as a function of wave frequency, water depth, permeability, Poisson's ratio, rigidity, and specific loss of bed soil. Three types of elastic waves are induced in a bed by water waves: a shear wave and a compressional wave in the skeletal frame of soil, and a compressional wave in the pore fluid. The compressional wave, due to the motion of the pore fluid relative to the skeletal frame of soil, is highly damped by the viscosity of pore fluid and only a short range effect near the boundaries of discontinuity, such as a sea‐seabed interface. The seabed response to water waves is characterized by the two Mach numbers, i.e., the ratio of water‐wave speed to shear‐wave speed in soil and the ratio of water‐wave speed to compressional‐wave speed in soil. Most of the water‐wave propagation problems fall into the subsonic flow condition, where elastic waves in the bed travel faster than water waves. For sandy beds, generally the speeds of compressional and shear waves are much higher than the phase velocity of the water wave. For this case, the solution of the Coulomb‐damped poroelastic bed response presented in this paper approaches the solution of the massless poroelastic bed response in Yamamoto et al. (1978 [Jour. Fluid Mech., 87(1): 193–206]). The damping of water waves due to internal grain‐to‐grain friction is equally or more significant than the damping due to percolation in sand beds. For clay beds, the speed of the shear wave in soil becomes low and comparable to the phase speed of the water wave. The bed motion for this case is considerably amplified due to the near‐resonance vibration of shear mode of bed vibration. The water wavelength on a clay bed is significantly shortened compared to the water wavelength over a rigid bed. The water wave damping due to internal grain‐to‐grain friction in soil becomes much larger compared to the water wave damping due to percolation in clay beds. Long water waves over a soft clayey bed attenuate within several wavelengths of travel distance. 相似文献
13.
1 .IntroductionRecently, more and more importance is attached to the development of offshore oil and gas alloverthe world and many submarine pipelines have been laid.Submarine pipelines are the lifeline ofthe transportation of offshore oil and gas .Submar… 相似文献
14.
《中国海洋工程》2020,(3)
The pipe-soil interactions at shoulders can significantly affect the vortex-induced vibrations (VIV) of free-spanning pipes in the subsea. In this paper, the seabed soil reacting force on the pipe is directly calculated with a nonlinear hysteretic soil model. For the VIV in the middle span, a classic van der Pol wake oscillator is adopted. Based on the Euler-Bernoulli beam theory, the vibration equations of the pipe are obtained which are different in the middle span and at the two end shoulders. The static configuration of the pipe is firstly calculated and then the VIV is simulated.The present model is validated with the comparisons of VIV experiment, pipe-soil interaction experiment and the simulation results of VIV of free-spanning pipes in which the seabed soil is modelled with spring-dashpots. With the present model, the influence of seabed soil on the VIV of a free-spanning pipe is analyzed. The parametric studies show that when the seabed soil has a larger suction area, the pipe vibrates with smaller bending stresses and is safer.While with the increase of the shear strength of the seabed soil, the bending stresses increase and the pipe faces more danger. 相似文献
15.
针对不规则波浪作用下Wigley型船的运动响应问题进行了系统的研究,采用统计学方法深入探讨了船舶不规则运动幅值和响应周期的分布规律,并通过傅里叶变换对船舶运动响应进行了频谱特征分析。结果表明,船舶横摇方向与升沉和纵摇方向随机运动的响应特征有显著差异。在升沉与纵摇方向,波浪谱峰频率远离自振频率,前十分之一大振幅运动对应周期离散性较小,基本稳定在波浪谱峰周期附近,但小振幅运动周期分布离散性较大,频谱分析指出船舶升沉与纵摇运动响应频谱在波浪谱峰频率附近出现明显峰值。而在横摇方向,波浪谱峰频率与自振频率相耦合,不同振幅的横摇运动响应周期均稳定在自振周期附近,且周期离散性较小,频谱分析也表明横摇运动响应频谱主要集中于船舶运动自振频率附近。 相似文献
16.
Extreme waves can induce seepage in a seabed and cause problems to marine structures in coastal regions. In this study, the seepage under cnoidal waves was studied using the transient seepage equation. An analytical solution is presented for the pore pressure in a seabed of defined thickness. Parametric studies were carried out to examine the influence of air content in the pore water, and of the soil hydraulic conductivity on the seepage. It has been shown that the air content and the soil hydraulic conductivity can affect the pore pressure response significantly. An increase in the air content or a decrease in the soil hydraulic conductivity will increase the magnitude of the pore pressure gradient and results in the pore pressure varying sharply. The liquefaction potential of a seabed under cnoidal waves is discussed. Consequently, comparative studies are carried out to show that the soil shear modulus and Poisson constant can influence the difference between the transient seepage equation and Biot's equation, and the transient seepage equation is a limit of Biot's equation. 相似文献
17.
As an important part of lifeline engineering in the development and utilization of marine resources, the submarine fluid-filled pipeline is a complex coupling system which is subjected to both internal and external flow fields. By utilizing Kennard’s shell equations and combining with Helmholtz equations of flow field, the coupling equations of submarine fluid-filled pipeline for n=0 axisymmetrical wave motion are set up. Analytical expressions of wave speed are obtained for both s=1 and s=2 waves, which correspond to a fluid-dominated wave and an axial shell wave, respectively. The numerical results for wave speed and wave attenuation are obtained and discussed subsequently. It shows that the frequency depends on phase velocity, and the attenuation of this mode depends strongly on material parameters of the pipe and the internal and the external fluid fields. The characteristics of PVC pipe are studied for a comparison. The effects of shell thickness/radius ratio and density of the contained fluid on the model are also discussed. The study provides a theoretical basis and helps to accurately predict the situation of submarine pipelines, which also has practical application prospect in the field of pipeline leakage detection. 相似文献
18.
An integral description of the propagation of steady-state perturbations of the heavy liquid surface
The system of equations of motion describing the gravity wave propagation in a perfect heavy liquid layer is transformed into
a new integral equation for the free surface elevations. In the limit cases, this integral equation describes the linear and
nonlinear periodic waves as well as the known types of solitary waves. In this case a dispersion equation arises because perturbations
of the second and higher orders of smallness are neglected. The integral equation allows for the propagation of invariable
surface perturbations of arbitrary forms if their spatial spectrum is concentrated near small wave numbers (compared to the
inverse wave amplitude). Several examples of solutions are presented. 相似文献
19.
Experimental Study on Vortex-Induced Vibrations of Submarine Pipeline near Seabed Boundary in Ocean Currents 总被引：2，自引：3，他引：2
1 .IntroductionThe submarine pipeline is a commonfacility widely usedfor offshore oil and gastransport . Whena pipeline is installed on a seabed and not buried,unsupportedspans may exist insomelocations ,es-peciallyinthe uneven zones of the seabed.The spa… 相似文献
20.
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