Effects of Irregular Wave Groups on Pile Forces

The wave forces on 1,2 and 4 vertical circular piles under the action of several wave trains of the same wave parameters, such as Hs Tp and Mo, but different wave group factors GF are measured in the laboratory. After comparing these forces, it may be concluded that the mean and significant wave forces are almost of no difference for the wave trains with different GF. When GF is larger, the one-tenth of the wave force extreme is slightly increased and the maximum wave force is much larger than the ones with smaller GF, to which attention must be paid in engineering practice.

Wave Breaking Phenomena of Irregular Waves Combined with Opposing Current

Experimental study and theoretical analysis show that the critical value of relative wave height (H / d)b given by Goda and the critical wave steepness (H / L)b given by Michell and Miche can be adopted as the spilling breaking indices of regular waves. According to the same principle, a systematic theoretical analysis and experiment of irregular wave have been done by the authors in order to solve the breaking problem of irregular waves. It is indicated that the authors' method for determining wave breaking of regular waves can also be used for irregular waves.

MODEL STUDY OF DREDGED CHANNEL SILTATION IN OFFSHORE OPEN WATER

Based on the model study, the siltation of dredged channel under the condition of clear water and sediment-water mixture in Lianyun Harbor, Jiangsu Province and the experimental method under complex hydrodynamic elements such as tides, winds, waves and tidal currents are studied. The regularities of the variation of the velocity in the dredged channel in clear water are discussed as well. A group of curves such as water depth, velocity and angle has been plotted as a guide to the selection of a proper direction for a dredged channel. The intensity of siltation and the rate of deposition in the condition of sediment-water mixture, and the relationship between the dimensions of the dredged channel and the deposition amount can be estimated.

INVESTIGATION AND APPLICATION OF LAWS OF TWO DIMENSIONAL TRANSFORMATION OF SANDY BEACHES UNDER WAVE ACTION

Based on previous research results and experimental studies, this paper indicates the important factors affecting two-dimensional transformation of sandy beaches, especially the characteristic slope and sediment transport factor. A discrimination criterion of transformation type of sandy beaches is derived by applying the theory of wave energy dissipation rate. This criterion is closely examined with a lot of data and can be used to forecast the transformation of sandy beaches under the action of varying wave climates.

Response of Coastal Groundwater Table to Offshore Storms

Large groundwater table fluctuations were observed in a coastal aquifer during an offshore storm. The storm induced significant changes of the mean shoreline elevation, characterized by a pulse like oscillation. This pulse propagated in the aquifer, resulting in the water table fluctuations. A general analytical solution is derived to quantify this new mechanism of water table fluctuation. The solution is applied to field observations and is found to be able to predict reasonably well the observed storm induced water table fluctuations. Based on the analytical solution, the damping characteristics and phase shift of the oscillation as it propagates inland are examined.

TRANSVERSE FORCES ON VERTICAL PILE IN REGULAR AND IRREGULAR WAVES

The magnitude and the fluctuating frequency of the total transverse wave forces, particularly those by irregular waves on an isolated pile are investigated experimentally. The results indicate that the transverse force (FL) is usually not negligible and the resultant force (FR) of the transverse force and the inline force may be 40% (in regular waves) or 18% (in irregular waves) larger than the inline force (F). The plots of FL/F, FR/F and several kinds of lift coefficient CL versus KC number are given for both regular waves and irregular waves. The methods for estimating the total transverse forces and resultant wave forces are suggested.

Hydrodynamic Forces on Inclined Cylinder due to Waves with Crossing Current

Based on Morison's Equation and linear wave theory, hydrodynamic forces acting on inclined cylinders due to waves and crossing current at an angle of αs are analyzed. A method for calculating exciting forces is proposed. Experimental results show that the proposed method in this paper is feasible and can be used in engineering practice.

Model Study of Permeable Caisson Breakwater with Slanting Slabs

This paper describes the design of a permeable caisson breakwater with slanting slabs (Types I and II) and presents some preliminary experimental results, together with relevant figures and tables. Analysis is made of the reflection coefficient, transmission coefficient, acting wave pressures, water jetting at the crest of the breakwater, and wave overtopping. Experiments show conclusively that this type of breakwater has the advantages of light dead weight, good wave-absorbing performance, low coefficients of reflection and transmission, and small wave overtopping.

UNIFIED EQUIVALENT HARMONIC LOADING ON SEABED FOUNDATIONS UNDER RANDOM WAVE LOADING

In accordance with laboratory tests and theoretical analysis, the concept of unified equivalent harmonic wave loading is suggested and discussed in this paper. Such a concept may be more reasonable and widely applicable in offshore foundation engineering. A verification test has also been completed, in which the random wave loading and the corresponding unified equivalent loading were applied on soil samples. The test results show that the equivalent effect is satisfactory.

The study on the bottom friction and the breaking coefficient for typhoon waves in radial sand ridges—the Lanshayang Channel as an example

Owing to the interactions among the complex terrain, bottom materials, and the complicate hydrodynam-ics, typhoon waves show special characteristics as big waves appeared at the high water level （HWL） and small waves emerged at low and middle water levels （LWL and MWL） in radial sand ridges （RSR）. It is as-sumed that the mud damping, sandy bed friction and wave breaking effects have a great influence on the typhoon wave propagation in this area. Under the low wave energy, a mud layer will form and transport into the shallow area, thus the mud damping effects dominate at the LWL and the MWL. And high Collins coef-ficient （c around 1） can be applied to computing the damping effects at the LWL and the MWL. But under the high wave energy, the bottom sediment will be stirred and suspended, and then the damping effects disappear at the HWL. Thus the varying Collins coefficient with the water level method （VCWL） is imple-mented into the SWAN to model the typhoon wave process in the Lanshayang Channel （LSYC） of the RSR, the observed wave data under “Winnie” （“9711”） typhoon was used as validation. The results show that the typhoon wave in the RSR area is able to be simulated by the VCWL method concisely, and a constant wave breaking coefficient （γ） equaling 0.78 is better for the RSR where wide tidal flats and gentle bed slopes exist.

浅水爆炸冲击波特性及其毁伤效应研究进展

为阐明浅水爆炸条件下冲击波界面效应,分别从自由水面、水底以及自由水面和水底两个界面双重作用条件下归纳了冲击波线性反射和非线性反射理论、实验等研究进展。总结了浅水区混凝土障碍、舰船毁伤方式,分析了由于界面作用以及装药、起爆方式等的差异而导致冲击波在近场的非均匀分布性,采用爆炸能量调控改变在特定方位能量输出,从而提升浅水爆炸毁伤效应的可行性。指出浅水爆炸理论发展仍未完善,浅水爆炸近场能量结构控制、混凝土目标动态响应和毁伤效应,界面反射冲击波与气泡相互作用是重点研究方向。附参考文献129篇。

悬挂式矩形水墙对爆炸冲击波削减效果的实验研究

为探究开放空间中水对爆炸冲击波的削减效果,基于水平激波管搭建了冲击波与悬挂式矩形水墙相互作用的实验平台,在水墙近场位置开展了8组实验。利用高速纹影测试系统记录冲击波与水墙的相互作用过程,并研究水墙厚度对水墙破碎效果以及运动速度的影响。利用压力测试系统记录水墙后方的压力变化,并结合高速纹影测试结果进行分析。结果表明:水墙后方的压力变化与冲击波的反射、透射以及绕射现象无关,主要取决于水墙产生的冲击作用;动量提取为悬挂式矩形水墙的主要减爆机制;水墙对冲击波峰值压力具有明显的削减效果,且随着水墙厚度的减小,对峰值压力的削减效果逐渐增加;水墙对峰值冲量的削减效果并不明显。

黄河口粉土强度丧失与恢复过程现场振动试验研究

在黄河口潮坪上选择典型研究区,进行了模拟波浪荷载的现场振动试验,利用轻型静力触探仪测记振动前、振动刚刚结束以及静置一段时间后土体贯入阻力的强度值,研究了海床土强度的丧失、恢复过程及影响因素。研究结果发现:模拟波浪荷载振动导致土体强度丧失发生在海底面下一定深度范围内,强度丧失量和恢复量沿深度呈抛物线型变化。振动后,土体表面排出的水和细粒物质环绕振动点周围形成一系列微型“泥火山”。振动导致土强度最大恢复量值与强度最大丧失量值出现在同一深度处;振动结束 2 h 后,土体强度超过振动前原状土体强度,振动使土体强度丧失与恢复受土体曾经历的水动力作用强弱、振动前土体的原始强度、振动荷载的循环次数、振动能量大小、土体的深度、静置的时间等因素的影响显著。黄河口海床土体强度独特变化规律的成因机理有待进一步研究。

潜体波浪中近水面不同潜深和航向时运动和波浪力计算

本文对潜水细长体波浪中近水面运动和波浪力的计算 ,采用STF理论和Frank源分布紧密拟合方法预报波频运动和波浪力响应 ;采用Newman细长体方法和3-D修正处理计算垂直面低速潜体的二阶平均波浪力与力矩。该方法和计算程序的实用性和可靠性已经被多次模型试验结果比较、验证所证实。本文以某一国外典型潜艇为例 ,计算了七种潜深、七种相对浪向下艇体的近水面波频运动响应与波浪力响应 ,给出了几种运动与波浪力参数随潜深变化与浪向变化的计算实例。

海岸带波浪破碎区污染物运动的实验研究

由于波浪在岸滩上的演化、破碎使得污染物在海岸带的运动规律变得十分复杂。通过实验模拟,研究了缓坡海岸(坡度为1∶100和1∶40)波浪破碎区污染物的运动规律,给出了不同时刻污染物在该区域的运动变化趋势。讨论并分析了在斜向规则入射波、不规则入射波及不同入射波波高作用下污染物在沿岸波浪破碎区域的运动变化方向和相应的运动范围分布规律。给出并分析了近岸波浪破碎区域污染物运动分布规律。

二维数值水槽波浪生成过程及波浪形态分析

为了弥补物理模型试验投资大、模型相似性差等缺点,利用数学模型进行流体力学研究越来越普遍。基于物理水槽造波原理,在FLUENT流体软件中通过设定造波板边界的运动来模拟实际造波板的运动过程,实现了二维规则波的数值模拟,并给出了波高随造波板运动周期、振幅及坐标的变化规律。对波浪形态的分析表明,利用本文研究的数值模拟方法所生成的波浪符合实际造波形态。通过改变边界条件,用该方法也可以实现二维不规则波和随机波的数值模拟。

软土地基条件下大型圆筒海岸结构稳定性计算方法

针对一工程发生破坏的实例,对软土地基条件下大型圆筒海岸结构的设计与计算方法进行了比较分析,并对波浪水流作用下软土特性参数的选取、泥面冲刷对结构稳定性的影响等进行了讨论。提出了反复荷载作用下软土的动力特性、水流作用下结构周围泥面的冲刷演变规律以及波浪作用下大型圆筒结构与软土的动力相互作用等,这都是软土地基条件下大型圆筒海岸结构工程应用亟待解决的关键问题。

波浪在V形贯底式防波堤上绕射的解析研究

给出了V形贯底式防波堤对波浪绕射计算的解析方法.假定防波堤刚性、薄壁、不透浪,水深恒定.假想存在一个圆柱面,把流场划分为3个区域,在每个区域上将速度势用特征函数展开,在它们的公共边界上进行匹配.匹配的原则是公共边界上速度、压力连续,得到关于未知系数的一组线性代数方程组,解出未知系数,即可求得流域中任意一点的速度势和波高.通过与已有的平直岛式防波堤绕射解析解比较,说明该方法是正确可靠的.数值结果给出了不同入射波频率及防波堤两臂不同张角时防波堤周围波幅的等高线图.结果表明:V形贯底式防波堤具有很好的防浪效果,通常情况下,掩护区域内的波高仅为入射波波高的20%～50%.

无舱盖船舶甲板上浪的研究

研究船舶甲板上浪的问题是设计无舱盖船舶的重要前提 .甲板上浪和近海建筑物的越浪相似 ,均为非线性物理现象 ,因此引入越浪理论对规则波激励下的航行船舶甲板上浪量进行推算 ,利用洪水波理论与越浪理论相结合的方法对甲板上浪越过舱口舷板的船舱进水量进行计算 .模型实验表明 ,理论计算与实验结果较为吻合 .

拖航系统在风浪中操纵运动的模拟计算

本文建立了风浪中拖航系统(包括拖船—拖缆—被拖船)的操纵性运动的数学模型 ,并以1940kw拖船与8820t甲板驳以及15760t半潜驳为例 ,分析了航速、缆长、载重量、纵倾和环境条件对拖航系统的运动与拖缆力的影响。