Preservation potential of individual couplet and deposition rates on mudflats in the Changjiang Estuary

Non-barrier mudflats in the Changjiang Estuary is examined to obtain preservation potentials and deposition rates over different time scales. The preservation potential of couplet is ca. 46.6% within daily scale and decreases as the time-interval extending, with 9.2% on a semi-lunar scale and 3.7% on a seasonal scale. In the long term, only 1.6% of daily deposition can potentially be preserved in the tidal flat sequence and other 98.4% have been eroded and leave sedimentary discordances, discernable or un-discernable, in the mudflat deposits. A negative log-linear relationship is examined between sedimentation rates and the time spans. The length of sedimentary hiatuses on the mudflat deposition were estimated with considerable uncertainty, but it can provide from an actualistic base some further insights into the nature and origin of ancient mudflat deposits with emphasis on the sedimentary discordances.     

A three-dimensional baroclinic current model with wave effects

Waves can have a significant impact on nearshore currents. A three-dimensional baro-clinic current model including the influence of waves is presented for shallow water areas from Navier-Stokes equations. It has been found that the effects of waves on currents can be expressed in terms of the momentum flux by waves. The model uses non-orthogonal curvilinear coordinates in the horizontal directions and a Sigma coordinate in the vertical direction so that it can be more reasonably applied in estuarine and coastal regions.     

Extended Mild-Slope Equation

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广义缓坡方程

运用表面波Hamilton方程和缓坡逼近假定,分析缓主为三维流场和非平整海义对波浪传播的影响,推导出广义缓坡方程,海底地形由两个分量组成,慢变分量,其水平长度尺度大于表面波的波长,快变分一,其振幅与表面波的波长相比为一小量,但是其频率与表面波频率相当,该广义缓坡方程具有广泛的适用范围,以下著名的缓坡方程成为它的特例,经典的Berkhoff缓坡方程,包含环境流效应的Kirby缓坡方程,描述波状海底特征的Dingemans缓坡方程,另外,也得到了描述环境流场和快变海底效应的广义浅水方程。     

海浪能量的外观分布

本文明确提出了海浪能量外观分布的概念,并将其简称为“外频谱”以便区别于通常的海浪频谱。文中依据作者先前提出的海浪波高与周期的联合分布,从理论上首次导出了外频谱的一种三参量Cauchy型解析分布形式,并简要讨论了外频谱与通常海浪频谱之间存在某种相似性的力学根据。鉴于Bretschneider谱一直被视为通常的海浪频谱而在工程中广泛应用,文中还考虑了将Cauchy型外频谱作为通常海浪频谱使用的可能性与优越性     

非线性海浪的波面高度概率分布及其物理解释

依据非线性随机海浪模型,通过直接求矩的方法,在三阶近似下导出了一种普遍适用的海浪波面高度统计分布,并解释了它的物理含意。对于深水,且仅考虑两类最简单的波-波相互作用,则此分布在精确至H_6的意义下蜕化为Longuet-Higgins给出的Gram-Charlier级数。     

三维缓变流场上波浪折射—绕射的缓坡方程

运用Luke变分原理,建立了波浪在三维缓变流场中和缓变海底上折射-绕射的一般缓坡方程,据此给出了在几何-光学逼近（△↓S)^2=k^2有效时,波浪、环境流和海底坡度必须满足的若干条件,对一般缓坡方程进行了分类,在一种特定流场结构的假定下,得到了方程的行波解。     

Seasonal changes in coastal dynamics and morphological behavior of the central and southern Changjiang River delta

Seasonal changes in sea level, tidal range, wind, riverine discharges, nearshore SSC (suspended sediment concentration) and bed-level of intertidal flat at 4 different sites were shown. In addition, the statistical relationships between the dynamics and the behavior of the sediment surface were examined. The average intertidal elevation seems negatively correlated to sea level while positively correlated to nearshore SSC. The effect of wind on seasonal cycle of average intertidal elevation is not evident although wind is an important factor governing short-term erosion/accretion events. The influence of riverine discharges on seasonal cycle of deltaic intertidal flats is masked by other factors. It is concluded that seasonality on mudflats is more complicated than on beaches.     

A preliminary study on sea wave packet equations on slowly varying topography

There is a common hypothesis for the presently popular mild-slope equations that wave particle motion is irrotational. In this paper, an attempt is made to abandon the irrotational assumption and to set up new sea wave packet equations on slowly varying topography by use of the WKBJ method. To simplify the deduction, the two-dimensional shallow water equations are used to describe the sea wave particle motion in the very shallow nearshore area. The established equations can give some characteristics of wave propagation near shore.     

非均匀水流水域波浪的传播变形

将两个不同的、考虑波流相互作用和能量耗散项的、依赖时间变化的双曲型缓坡方程分别化 为一组等价的控制方程组，具体分析了底摩阻项对相对频率和波数矢的影响，从而选择了合 适的数学模型. 将所选择的缓坡方程化为依赖时间变化的抛物型方程，并用ADI法进 行数值求解，建立了缓变水深水域非均匀水流中波浪传播的数值模拟模型. 通过和波流共线 的解析解的比较，说明数值解和解析解相一致. 结合Arthur(1950)水流这一经典算例，定 量地讨论了考虑联合折射-绕射作用后的波数和仅考虑折射作用的波数的差别及其对波高分 布的影响. 在基本同样的条件下, 本文的数值解与他人的计算结果一致.