Study on Influences of Fringing Reef on Harbor Oscillations Triggered by N-Waves

Influences of topographic variations of the offshore fringing reef on the harbor oscillations excited by incident Nwaves with different amplitudes and waveform types are studied for the first time. Both the propagation of the Nwaves over the reef and the subsequently-induced harbor oscillations are simulated by a Boussinesq-type numerical model, FUNWAVE-TVD. The present study concentrates on revealing the influences of the plane reef-face slope,the reef-face profile shape and the lagoon width on the maximum runup, the wave energy distribution and the total wave energy within the harbor. It shows that both the wave energy distribution uniformity and the total wave energy gradually increase with decreasing reef-face slope. The profile shape of the reef face suffering leading-elevation Nwaves(LEN waves) has a negligible impact on the wave energy distribution uniformity, while for leading-depression N-waves(LDN waves), the latter gradually decreases with the mean water depth over the reef face. The total wave energy always first increases and then decreases with the mean water depth over the reef face. In general, the total wave energy first sharply decreases and then slightly increases with the lagoon width, regardless of the reef-face width and the incident waveform type. The maximum runup subjected to the LEN waves decreases monotonously with the lagoon width. However, for the LDN waves, its changing trend with the lagoon width relies on the incident wave amplitude.     

Resonance Induced by Edge Waves in Hua-Lien Harbor

This article first reviews previous numerical studies on the resonance problem of Hua-Lien Harbor. All the research leads to the conclusion that resonance can be stimulated by 2-D infragravity waves. However, a literature survey suggests that outside the harbor these plane infragravity waves are too small to excite violent water-body movement inside. On the other hand, 3-D infragravity waves trapped along the coastline, also known as edge waves, are more likely to exist outside the harbor and their effect needs to be thoroughly discussed. Based on previous measurements, the response of Hua-Lien Harbor is best simulated using edge waves of 160 and 140 second periods and their resonance mechanisms are analyzed. The former case has a longitudinal resonant mode and hence the amplitude in the inner harbor is large. The latter case has a transverse mode in the outer basin and hence only berths in the outer basin are influenced. These features are both consistent with field measurement. Therefore, it is very likely that edge waves are responsible for the resonance of Hua-Lien Harbor. Finally, based on observation after the construction of the present offshore breakwaters, a theory is proposed to explain the trapping of incident edge waves, and a measure to further reduce the resonance is discussed.     

Numerical Analysis of Hydrodynamic Pressure Induced by Fluid-Solid Impact

—As a further development of the authors'work(Huang and Qian,1993),in this paper a newnumerical method based on the time domain boundary element technique is proposed for solving fluid-sol-id coupling problems,in which a rigid body impacts normally on the calm surface of a half-space fluid.Afundamental solution to the half-space potential flow problem is first derived with the method of images.Then,an equivalent boundary integral equation in the Laplace transform domain is established by meansof Green's second identity.Through the inverse Laplace transform and discretization in both time andboundary of the fluid region,the numerical calculation for the problem under consideration has been car-ried out.Several examples demonstrate that the present method is more efficient than existing ones,fromwhich it is also seen that the shape of the impacting body has a considerable effect on the total impactforce.     

港池泊稳的能量平衡方程数值模拟

对基于能量平衡方程的多向随机波浪传播数学模型进行改进,通过模拟不同防波堤绕射引起的港池泊稳,验证模型的合理性和有效性。利用非线性弥散关系提高模型计算浅水变形的精度;采用二次逆风差分格式离散控制方程,避免了加入绕射项引起的数值耗散;并将文氏谱加入模型中,使其更加适合中国海域的工程应用。应用改进后模型绘制的双突堤和岛式防波堤绕射系数图与我国《海港水文规范》图进行了对比。对比结果十分接近,可以较好地描述港池的泊稳状况,为综合计算波浪在近岸的浅水变形、折射、绕射、反射和能量耗散等作用奠定了基础。     

海阳中心渔港建设对附近海域冲淤的数值模拟预测

利用MIKE21二维水动力模型,对海阳中心渔港建设前,以及两种预选方案建设后海域潮流分别进行数值模拟。在潮流模拟验证正确的基础上,建立了海底冲淤预测模型,预测了工程建设前后静风条件下全年冲淤趋势。并运用MIKE21Coupled ModelFM模块,模拟了极端天气条件（SE15m/s大风）浪流共同作用下工程附近海域的冲淤情况。根据方案建设前后潮流场、冲淤趋势进行分析,确定最优方案,为海阳中心渔港的规划设计提供决策参考。     

Numerical Modeling of Meteorological Sea Level Oscillations in the Black Sea

Oceanology - To study the features of short-period meteorological sea level oscillations, adaptation of the numerical Princeton Ocean Model (POM) to the Black Sea conditions was performed. The...     

Numerical Calculation Methods for Wavemaking Response Induced by Explosion in Harbour

Using the axial symmetry results of marker and cell (MAC) method as initial value in this paper, two numerical calculating methods are presented for the late wavemaking response induced by explosion in harbour. One of the methods is the superposition method of the vibration mode based on fluid slosh in container. Another one is the joining method of the MAC results with the shallow wave theory calculation in time domain. As a practical example, it is conducted to the numerical calculation about 1000 ton TNT equivalent explosion within touch of water surface. The results show that it can be rationally described with the methods to the wavemaking progress and character. The numerical results are identical with the observed scene on the spot experiment. The methods are simple and applicable in the engineering design.     

结构海床耦合系统动力分析数值模型及考察

基于改进的哈丁模型建立了结构海床耦合系统的等效线性化动力分析模型。等效阻尼比是对土体进行等效线性化分析的重要组成,论文着重对土体阻尼对结构海床耦合系统的影响效应进行了考察。接触面分离力是运用滑动库仑摩擦模型进行接触面效应模拟的重要参数,在以前的工作基础上,文中提出了新的结构-海床接触面分离力模型并进行了考察,使其更符合实际情况     

基于MIKE SA模型的厦门西港海域溢油影响的数值模拟研究

基于MIKE SA溢油模块,以燃料油为油种,建立了厦门西港海域溢油模型,模拟静风、主导风向（东北东风）和不利风向（西南风）3种风场条件下,一个潮周期内涨急、高潮、落急和低潮4个时段发生10 t溢油后油膜的漂移路径和影响范围.结果显示,发生在厦门西港海域的溢油在海面的漂移过程主要受潮流和风的影响,其中潮流起着主导作用.不同风向条件下,24 h内油膜的影响范围不同,静风条件下溢油浓度超一类（或二类,≥0.05 mg/dm3）、超三类（≥0.30 mg/dm3）和超四类（≥0.50 mg/dm3）的总影响面积分别为31.33、19.63和11.74 km2;主导风向条件下溢油浓度超一类（或二类）、超三类和超四类的总影响面积分别为99.62、69.01和8.99 km2;不利风向溢油浓度超一类（或二类）、超三类和超四类的总影响面积分别为8.38、5.05和2.10 km2.该预测结果可给出溢油事故发生后的影响范围、影响程度和影响敏感目标的时间,可为溢油事故应急决策的制定及溢油损害评估提供科学决策和支持,提升厦门海域环境风险管理应急能力建设.     

日照帆船港港域波高的数值计算

考虑波浪的浅水变化、折射、绕射、反射和破碎等现象的影响,以文氏谱作为输入谱,建立了浅水区域随机波浪传播变形的改进数值模型。对日照帆船港港域波高的数值计算结果表明:在没有越浪的情况下,计算值与物理模型试验观测值吻合。改进的数值模型成为求解港口水域波高的1种有效方法。     

Numerical assessment of bathymetric changes caused by the 2004 Indian Ocean tsunami at Kirinda Fishery Harbor,Sri Lanka

Thus far various numerical models have been developed and improved to aid understanding of the sediment transport process due to tsunamis. However, the applicability of these models for the field-scale bathymetric change remains a major issue due to the scarcity of measured bathymetric data immediately before and after tsunamis. This study focuses on assessing the applicability of the sediment transport model by comparing the model results with measured bathymetry data obtained one month before and two months after the 2004 Indian Ocean tsunami at Kirinda Fishery Harbor, Sri Lanka. Obtained model results were compared with measured data along four different transects. In particular, similar to the measured data, the model reproduced the bed level change at the harbor mouth well, although it shows some discrepancy on bathymetric change along the shoreline, which is directly affected by littoral drift. Therefore, it is noted that the divergence of reproducing the local bathymetry change is due to the normal wind wave effect on measured data and the model limitations. Hence we included the wind wave effect in modeled data and the discrepancy between measured and modeled data was reduced. Furthermore, the modeled bed level change indicates a dynamic behavior in terms of the net variation during the tsunami flow, such that deposition dominates in the inflow and erosion dominates in the backflow. Both bed level variation and the suspended load concentration reveal that the large amount of eroded sediment attributable to tsunami waves was in suspended form and was deposited in the nearshore area after the water fluctuation had abated. The model results further indicate that eroded sediment at the initial depth deeper than 11 m might be brought by the incoming tsunami waves and deposited in the nearshore area where the depth is shallower than 7 m.     

矩形双曲余弦型水深港池振荡的数值模拟

为了研究由涌浪引发的港口横向振荡,采用完全非线性Boussinesq数值模型FUNWAVE 2.0模拟了双曲余弦型水深的矩形港池内(1,1)模态的横向振荡。研究表明,只有在港池底部设置微小横向坡度,才能成功地激发横向震荡;而在横向水深不变的情况下,无法激发明显的横向振荡。通过分析纵向坡度、横向坡度和入射波高对横向振荡的影响,了解了横向坡度的影响:当横向振荡幅值较小时,它与横向幅度保持线性关系;横向振荡的幅值较大时,它受到非线性强度的限制,增长缓慢。在纵向坡度较大,入射波高较小时,横向振荡的幅值经过一定时间的增长,能超过纵向振荡并主导港内的水体运动。所有横向振荡都是非线性作用的结果,而非单纯的由地形变化产生的绕射导致的。     

Numerical Investigations on Hydrodynamic Performance of An Open Comb-Type Breakwater Under Medium Water Levels

China Ocean Engineering - The comb-type breakwater (CTB) has been proposed and investigated in recent years due to its advantages in terms of deep-water adaptability, material saving and water...     

Oscillations in a coupled bay—river system. 2. Numerical method

Natural and wave-induced oscillations in Nagasaki Bay, a coupled bay—river system, are numerically studied. Formulation of the problem is based on the mild slope wave equation with modeled dissipation. Computations are performed by the finite element method originated from the classical variational principle. The numerical results show that the bay at the mean tidal level has natural modes of periods of 30.60 minutes, 17.28 minutes, 10.08 minutes, 7.67 minutes, etc. The 30.60-minute mode of the bay is characterized by a monotonic increase of the amplitude of oscillation from the bay entrance to the Urakami River mouth, whereas the 17.28-minute mode and the 10.08-minute mode attain maximum near Fukahori. It is also demonstrated that the 30.60-minute mode, the 17.28-minute mode and the 10.08-minute mode can be most severely resonated when the bay is subjected to oscillations in the open sea with periods of about 33.2 minutes, 17.9 minutes, and 10.1 minutes, respectively. The existence of the Urakami River seems to have an effect on mitigating the resonant bay oscillations, particularly if the relevant mode is of relatively low frequency and maximizes near the river mouth.     

Harbor resonance induced by subaerial landslide-generated impact waves

Past studies of harbor resonance have mainly been restricted to the quasi-steady oscillations induced by steady wave conditions. This paper investigates the response of a rectangular harbor to subaerial landslide-generated impact waves based on physical models, in order to compare the oscillations induced by steady and transient waves. In response to steady incident waves, oscillations within the harbor need to experience a long process to obtain their maximum value before the input energy and the losses are balanced. Landslide-generated impact waves usually include components with solitary wave characteristics and also components with dispersive wave characteristics. Each component travels with a different celerity. Usually, solitary wave components propagate faster, and arrive in the harbor first. Oscillations attain their maximum status as soon as these components arrive. The subsequently arriving components with dispersive characteristics do not enhance the resonance oscillations. So the waves with solitary characteristics are considered to play an important role in harbor resonance. Numerical experiments, using the FUNWAVE model, were conducted in order to further verify these conclusions.     

Numerical Simulation of Abnormal Wave Height Change Induced by Excavated Waterway with Boussinesq Equation

A nonlinear numerical model has been set up by use of Boussinesq Equation with finite differ-ence method,and has been applied to the simulation of the abnormal change of wave height induced by ex-cavated waterway.Numerical results demonstrate that the abnormal change of wave height is due to theadding of the reflected wave height induced by excavated waterway to the incident wave height.Becausethe angle between the incident wave and the axis of the waterway is smaller than the critical angle,the re-flected wave produced by the waterway may propagate to the breakwater and may be added with the inci-dent wave,then the abnormal change of wave height before the breakwater may be caused.So the wave re-flection caused by the change of water depth cannot be neglected.     

Numerical Prediction of Hydrodynamic Forces on A Berthed Ship Induced by A Passing Ship in Different Waterway Geometries

An investigation has been conducted to quantify the effect of waterway geometry on the form and magnitude of forces and moment experienced by a berthed ship due to a passing ship. By using the dynamic mesh technique and solving the unsteady RANS equations in conjunction with a RNG k?ε turbulence model, numerical simulation of the three-dimensional unsteady viscous flow around a passing ship and a berthed ship in different waterway geometries is conducted, and the hydrodynamic forces and moment acting on the berthed ship are calculated. The proposed method is verified by comparing the numerical results with existing empirical curves and a selection of results from model scale experiments. The calculated interaction forces and moment are presented for six different waterway geometries. The magnitude of the peak values and the form of the forces and moment on the berthed ship for different cases are investigated to assess the effect of the waterway geometry. The results of present study can provide certain guidance on safe maneuvering of a ship passing by a berthed ship.     

Experimental and Numerical Investigations of Ship Parametric Rolling in Regular Head Waves

Parametric rolling is one of five types of the ship stability failure modes as proposed by IMO. The periodic change of the metacentric height is often considered as the internal cause of this phenomenon. Parametric rolling is a complex nonlinear hydrodynamic problem, often accompanied by large amplitude vertical motions of ships. In recent years,the Reynolds-averaged Navier–Stokes(RANS) equation simulations for viscous flows have made great progress in the field of ship seakeeping. In this paper, the parametric rolling for the C11 containership in regular waves is studied both experimentally and numerically. In the experiments, parametric rolling amplitudes at different drafts, forward speeds and wave steepnesses are analyzed. The differences in the steady amplitudes of parametric rolling are observed for two drafts. The effect of the incident wave steepness(or wave amplitude) is also studied, and this supports previous results obtained on limits of the stability for parametric rolling. In numerical simulations, the ship motions of parametric rolling are analyzed by use of the potential-flow and viscous-flow methods. In the viscousflow method, the Reynolds-averaged Navier–Stokes equations are solved using the overset grid method. The numerical accuracies of the two methods at different wave steepnesses are also discussed.     

清澜港围滩工程前后潮流场的数值模拟

根据二维长波方程,用Ｌｅｅｎｄｅｒｔｓｅ分步隐式格式方法建立差分方程,计算了清澜港附近海域的潮流场,在此基础上还考虑了在计算域内实施用围滩造地和建造潜坝稳固沙咀工程后对计算域内流场的影响,得到了与实际观测值符合良好的结果。通过对多种工程方案前后流场及进出潮量的统计比较,为清澜港整治和合理开发提供了可靠依据。．     

葫芦岛港柳条沟港区规划潮流泥沙数模研究

建立了基于不规则三角形网格的考虑波浪作用的潮流泥沙数学模型,在对模型进行充分验证的基础上,对葫芦岛海域的潮流、泥沙场的进行了数值模拟,对该海区的潮流扬、泥沙场特征进行了分析;对萌芦岛港柳条沟港区规划方案进行了潮流、泥沙场模拟研究。详细分析了工程前后港池和航道的流扬变化,计算了航道的横流,预报了规划港区港池和航道的泥沙年淤积量,为港区的规划设计提供了科学依据。