Characteristics of Excess Pore Water Pressure of Nanjing Saturated Fine Sand Under the Interaction of Wave and Earthquake Loading

A stress path with continuous rotation of the principal stress direction and continuous alteration of amplitude of deviatoric stress difference under the interaction of wave and earthquake loading was proposed based on the characteristics of the stress path under wave and earthquake loading, respectively. Using a GDS dynamic hollow cylinder apparatus, a series of cyclic triaxial-torsional coupling shear tests were performed on Nanjing saturated fine sand via the stress path mentioned previously under different relative densities, effective initial confining pressures, plastic fines contents, and loading frequencies to study the development of excess pore water pressure (EPWP) of saturated sand under the interaction of wave and earthquake loading. It was found that the development of EPWP follows the trend of fast-steady-mutative-drastic, which is different from that under the cyclic triaxial test or wave loading. The number of cycles causing initial liquefaction (N_L) of saturated sand increases remarkably with relative densities. However, the relationships between N_L and effective initial confining pressures, plastic fines content, or loading frequencies are more complex.     

海浪对海洋上层的动量与混合作用分析

分析了波浪影响海洋环流的3种机制，给出了波浪对海流的雷诺应力表示、搅拌混合系数表示以及对温盐扩散的搅拌混合系数表示；计算了东中国海区域的波浪动量作用、搅拌混合系数空间分布和时间演化，进而定量分析了波浪对表层海流的动量输送及对海洋上混合层与跃层形成的作用。     

上层海洋中浪致混合研究评述——研究进展及存在问题

本文较系统地分析和总结了海浪在上层海洋中的混合作用研究的国内外现状,分别探讨了海浪破碎、波生运动以及波-湍相互作用导致的混合作用,指出了现有研究存在的问题。对今后研究做一展望,并指出实验室热分层水槽中的系统实验研究的必要性。     

Three-Dimensional Wave-Induced Current Model Equations and Radiation Stresses

After the approach by Mellor (2003, 2008), the present paper reports on a repeated effort to derive the equations for three-dimensional wave-induced current. Via the vertical momentum equation and a proper coordinate transformation, the phase-averaged wave dynamic pressure is well treated, and a continuous and depth-dependent radiation stress tensor, rather than the controversial delta Dirac function at the surface shown in Mellor (2008), is provided. Besides, a phase-averaged vertical momentum flux over a sloping bottom is introduced. All the inconsistencies in Mellor (2003, 2008), pointed out by Ardhuin et al. (2008) and Bennis and Ardhuin (2011), are overcome in the presently revised equations. In a test case with a sloping sea bed, as shown in Ardhuin et al. (2008), the wave-driving forces derived in the present equations are in good balance, and no spurious vertical circulation occurs outside the surf zone, indicating that Airy’s wave theory and the approach of Mellor (2003, 2008) are applicable for the derivation of the wave-induced current model.     

磨刀门河口枯季波生流场数值模拟研究

本文建立曲线坐标系下的双曲型缓坡方程波浪模型和考虑波浪辐射应力影响的深度平均2D潮流数学模型,首次研究了磨刀门河口2011年地形条件下的枯季波生流场。受波浪作用影响,落潮阶段,波浪作用方向与流向相反,在波浪顶托效应下拦门沙沙脊及外坡处流速普遍减小,形成两个主要回流区,口门外东西两侧浅滩处流速也减小,东西两汊及横洲深槽流速增大;涨潮阶段,波浪作用方向与流向相同,拦门沙沙脊及外坡处流速增大,沙脊处出现冲越流,口门两侧浅滩处流速增大,横洲深槽流速减小。     

考虑内流作用的缓波形立管非线性静动力分析

考虑内流的作用,研究缓波形立管在海洋环境荷载作用下的非线性静动力力学性能。采用细长柔性杆理论,建立缓波形立管运动方程,利用有限元法进行离散,运用Newton-Raphson法和Newmark-β法分别对立管进行静动力分析,编制缓波形立管计算分析程序LWRNM,研究缓波形立管在海流、内流、浮体漂移与运动作用下的结构响应。结果表明:随着海流从x负向变成x正向和流速的增大,缓波形立管线形变缓,有效张力增大,弯曲曲率的极值减小;随着内流流速的增加,缓波形立管的固有频率下降;随着顶部浮体从近端向远端漂移,缓波形立管的有效张力增大,弯曲曲率的极值减小;纵荡和垂荡作用下,缓波形立管的顶部有效张力变化周期与浮体激励周期相同,横荡作用下,顶部有效张力变化周期为浮体激励周期的二分之一,垂荡作用下,缓波形立管顶部有效张力变化幅值最大,纵荡作用下次之,横荡作用下最小。     

潜堤上规则波辐射应力的数值研究

在近岸波浪相关研究中,辐射应力是波动在水体中引起的剩余动量流,是波浪运动的重要物理量.在波浪从深水逐渐传向浅水的过程中,波浪的非线性逐渐增强,甚至会发生破碎等剧烈变形,引起辐射应力的强烈变化,对次重力波生成等有重要贡献.应用OpenFOAM精细模拟波浪在潜堤上的传播,得出波浪运动的详细流场信息,计算了有波浪破碎情况下潜...     

Exact solution and approximate solution of irregular wave radiation stress for non-breaking wave

Wave radiation stress is the main driving force of wave-induced near-shore currents. It is directly related to the hydrodynamic characteristics of near-shore current whether the calculation of wave radiation stress is accurate or not. Irregular waves are more capable of reacting wave motion in the ocean compared to regular waves.Therefore, the calculation of the radiation stress under irregular waves will be more able to reflect the wave driving force in the actual near-shore current. Exact solution and approximate solution of the irregular wave radiation stress are derived in this paper and the two kinds of calculation methods are compared. On the basis of this, the experimental results are used to further verify the calculation of wave energy in the approximate calculation method. The results show that the approximate calculation method of irregular wave radiation stress has a good accuracy under the condition of narrow-band spectrum, which can save a lot of computing time, and thus improve the efficiency of calculation. However, the exact calculation method can more accurately reflect the fluctuation of radiation stress at each moment and each location.     

荣喜近岸区波流耦合作用下的流场模拟

一方面将波浪对底部剪切应力、表面拖曳力系数,辐射应力以及表面混合长度的影响引入至COHERENS.另一方面又将水动力模型COHERENS和第三代波浪模型SWAN耦合,使两模型能够随时互相交换水流、水位以及波浪信息,最终获得波流耦合模型COHERENS-SWAN并将其应用于荣喜近岸区波流共同存在情况下的波流作用模拟研究.计算所得的流速、流向和水位与实测数据吻合较好.     

Threshold of Sediment Movement in Different Wave Boundary Layers

A review of former studies on the onset of sediment movement under wave action reveals that the Shields criterion obtained in unidirectional steady flow can also be applicable to oscillatory unsteady flow when the boundary layer is the same. In this paper, through comparison of different boundary layers in wave and steady flow conditions, a new criterion is presented which can be used to predict the threshold of sediment movement under wave action. The criterion curve shows good agreement with the experimental data.     

珊瑚礁海岸波流运动特性整体物理模型实验研究

根据现场地形在港池中建立三维珊瑚礁−潟湖−裂口海岸定床整体物理模型,采用波高传感器、流速仪和表面流速测量系统分别测量了规则波作用下珊瑚礁海岸不同位置的波浪和流场特征。结果表明：礁坪上,波高在向岸方向逐渐减小,总减小幅度为86.7%,增水先增大后减小,沿礁坪下降幅度为65.9%,水流以向岸流为主,存在着先增大后减小的趋势;潟湖中,波高靠近裂口处较大,中部最大值约为两侧最小值的2.8倍,增水则靠近裂口处最小,相比两侧最大值下降了25.5%,水流主要为对称地指向裂口的沿岸流,流速从两侧到裂口先增大后减小;裂口中波高变化不大,增水在靠近潟湖处最大,为礁坪上增水的47.6%,水流主要为离岸流,流速同样是先增大后减小。量化分析了环流驱动力、辐射应力与波面压力梯度的空间变化规律,发现礁坪上向岸流变化是平均水位梯度和辐射应力相互作用的结果,在裂口中的离岸流驱动力主要为辐射应力,而潟湖中的沿岸流变化由平均水位梯度决定的。     

非匀质波场波向对变风向响应现场观测设计

理论导出的非匀质波场波向对变风向响应的模式表明,单点波浪观测资料不足以提供非匀质情况下波向对变风向响应的信息。基于理论模式,提出了采用仪器阵列进行波浪观测研究波向响应的观测设计方案。     

The Mechanism Analysis of Seafloor Silt Liquefaction Under Wave Loading

The sediment in Chengbei area of the Huanghe (Yellow River) subaqueous delta is the object of a reseach project in this article. The accumulating and dissipating effects following the change of time are considered first in the study area and the distributing curves of excess pore water pressure along with time and depth in the soil stratum are gained; the possibility of silt liquefaction is evaluated using the computing values and the affecting depth of liquefaction is given. This paper quantitatively analyzes the dynamic response of seafloor soil under the cyclic loading of waves and makes an inquiry into the instable mechanism of soil.     

波场非匀质性对波向对变风向响应的影响

本文基于波能平衡方程，通过考虑波的传播项，即，研究波场非匀质性对波向对变风向的响应的影响。导出的结果表明，响应的时间尺度可由３部分表示：１．匀质情形响应的贡献；２．波能分布非匀质性的影响；３．平均波向分布非匀质性的影响。在理论上，它暗示波场的非匀质性在波向响应中起着实质性的作用；在实际情况下，对匀质和平稳风场，波场的非匀质性总是使响应时间尺度减少这一事实进行了讨论。     

波浪与抛石潜堤相互作用的MPS法数值模型研究

为了研究波浪与抛石潜堤相互作用过程中大自由表面变形和堤内渗流等强非线性紊流运动问题,利用改进的MPS法,建立了模拟波浪与抛石潜堤相互作用的MPS法数值计算模型。模型将抛石潜堤假定为均质多孔介质,采用Drew的二相流运动方程描述多孔介质内外的流体运动;通过在动量方程中增加非线性阻力项,并引入亚粒子尺度紊流模型,模拟波浪与可渗结构物相互作用过程中的紊流运动。选取"U"型管中多孔介质内渗流过程和孤立波与可渗潜堤相互作用两个典型的渗流问题,通过将数值计算结果与理论解和实测值的对比分析,对所提出的MPS法紊流渗流模型的模拟精度进行验证。结果表明:基于改进的MPS法构建的垂向二维紊流渗流模型可以很好地再现"U"型管中多孔介质内渗流以及波浪作用下可渗潜堤内外的复杂流场,显著缓解流-固界面处的压力震荡与粒子分布不均匀问题,实现了较高的模拟精度。     

波浪破碎诱导的海-气无机盐通量的参数化

波浪破碎诱导生成的海盐粒子是海洋向大气输运无机盐的主要机制,海气界面的无机盐通量对于全球气候变化有重要影响。本文开展了实验室实验模拟海盐粒子生成实验,定量考察了温度和盐度对海盐粒子中离子质量分布的影响,揭示了初生海盐粒子中各离子的富集和亏损现象与温度和盐度的关系。基于实验室观测分析结果和推测假定,提出了1个既包含海面风速、又反映海表温度和海表盐度影响的海-气无机盐通量参数化方案。将此参数化方案应用于估计海盐粒子向大气输运的各种无机盐离子质量通量,并与传统方法估算结果进行了比对分析。     

新型三维内波及分层流水槽系统

本文提供了作者研制的三维内波及分层流水槽系统的背景技术资料。经源致三维内波的实验证实 ,利用该水槽系统中的双缸制取分层水系统可快速制取所需的分层水 ,不必利用分子扩散而 1次得到预先设置的密度剖面。同时 ,还介绍了利用该水槽系统进行的 1个典型的源致内波的内波增阻实验。从所获得的增阻实验结果得知 ,对于一给定的分层、拖曳速度和水下回转体 ,存在唯一 1个内Froude数使得强迫源受到最大的内波增阻。大量的实验证实 :该水槽系统是研究三维自由和强迫内波的 1个基本实验系统。     

Numerical Prediction of Vortex Induced Vibrations on Top Tensioned Riser in Consideration of Internal Flow

In consideration of the effect of the internal flowing fluid and the external marine environmental condition on the vortex-induced vibration （VIV） of top tensioned riser （Till）, the differential equation is derived based on work-energy principles and the riser near wake dynamics is modeled by Facchinetti＇ s wake oscillator model. Then Galerkin＇ s finite element approximation is implemented to derive the nonlinear matrix equation of the coupled equations and file corresponding numerical programs are compiled which solve the coupled equations directly in the time domain. The comparison of the predicted results with the recent experimental results and the prediction of SHEAR7 is performed. The results show the validity of the proposed method on the prediction of VIV of deep water risers. The effect of internal flow on the dynamic characteristics and dynmnic response of the riser is analyzed and several valuable conelusions are drawn.     

Long-Period Distribution of Wave Heights and Its Application

This paper reveals that the long-period statistic distribution of the characteristic heights of deep-water waves assumes the lognormal distribution. Thereafter, the largest wave-height which may occur in the service life of coastal structures is derived in this paper.     

Joint Distribution of Wave Periods and Rate of Change of Wave Surface Elevation

The rate of change of wave surface elevation is of much importance in ocean engineering,es-pecially for the determination of the limitation of wave breaking.This paper gives a kind of joint distribu-tion of wave periods and the rate of change of wave surface elevation by means of calculation of the two-or-der to four-order moment of the frequency spectrum based on the linear wave theory.For the first time,the distribution density function of wave periods determined by peaks is provided,and the conclusion isdrawn that the rate of change of wave surface elevation obeys the Rayleigh distribution.