Numerical Simulation of Waves Interaction with A Submerged Horizontal Twin-Plate Breakwater

The numerical investigation of regular waves interacting with a submerged horizontal twin-plate breakwater is pre- sented in this paper. A numerical model with an absorbing wave-maker is established based on the VOF method. The validity of the model is verified by experimental results. Comparisons between the numerical and experimental results show that beth the water surface profiles and the wave-induced pressures can be modeled accurately. Wave deformation over the breakwater, water particle velocities around the breakwater, and the wave-induced pressures on the structure are nu- merically investigated. Tile pressure amplitudes of the fundamental and second harmonies on the model surface are exanl- ined in various water depths. The computed and experimental results have revealed that the higher frequency components are generated at the onshore side of the breakwater. Furthermore, the computed results demonstrate a circulating flow formed at the onshore side of the breakwater.

Analytical and Experimental Research on Wave Scattering by an Open-Type Rectangular Breakwater with Horizontal Perforated Plates

This study proposes a novel open-type rectangular breakwater combined with horizontal perforated plates on both sides to enhance the sheltering effect of the rectangular box-type breakwaters against longer waves.The hydrodynamic characteristics of this breakwater are analyzed through analytical potential solutions and experimental tests.The quadratic pressure drop conditions are exerted on the horizontal perforated plates to facilitate assessing the effect of wave height on the dissipated wave energy of breakwater through the analytical solution.The hydrodynamic quantities of the breakwater,including the reflection,transmission,and energyloss coefficients,together with vertical and horizontal wave forces,are calculated using the velocity potential decomposition method as well as an iterative algorithm.Furthermore,the reflection and transmission coefficients of the breakwater are measured by conducting experimental tests at various wave periods,wave heights,and both porosities and widths of the horizontal perforated plates.The analytical predicted results demonstrate good agreement with the iterative boundary element method solution and measured data.The influences of variable incident waves and structure parameters on the hydrodynamic characteristics of the breakwater are investigated through further calculations based on analytical solutions.Results indicate that horizontal perforated plates placed on the water surface for both sides of the rectangular breakwater can enhance the wave dissipation ability of the breakwater while effectively decreasing the transmission and reflection coefficients.

Experimental study on the wave loads of twin-plate breakwaterunder oblique waves

In this study, systematic physical model tests were performed to investigate the wave forces on the twin-plate breakwater under irregular waves. Based on the experimental results, the effects of the relative plate width B/L,wave height Hs/D and incident angle θ0 on the wave forces were analyzed and discussed. The results showed that:(1) The envelopes of the total wave pressure were generally symmetrical along the direction of plate width under the incident angles(θ0) being 0°, 15°, 30°, 45° and 60°. In particular, the envelopes of wave pressure atθ0=30° were larger than all other cases.(2) The synchronous pressure distribution of the breakwater under oblique wave action was more complicated comparing to the normal incident waves.(3) Based on data analysis, an empirical formula was obtained to estimate the total vertical force of the twin-plate breakwater.This empirical formula can be a good reference for the design basis of engineering applications under specified wave conditions.

Study on the Breakwater Caisson as Oscillating Water Column Facility

The Oscillating Water Column(OWC) wave energy convertor with the advantage of its simple geometrical construction and excellent stability is widely employed.Recently,perforated breakwaters have been often used as they can effectively reduce the wave reflection from and wave forces acting on the structures.Considering the similarity between the compartment of perforated caisson and the air chamber of OWC wave energy convertor,a new perforated caisson of breakwater is designed in this paper.The ordinary caisson is modified by installing facilities similar to the air chamber of OWC converter,but here they are utilized to dissipate the wave energy inside the caisson.Such an arrangement improves the stability of the caisson and reduces the construction cost by using the compartment of perforated caisson like using an air chamber.This innovation has both academic significance and important engineering value.For a new type of caisson,reliability analysis of the structure is necessary.Linear potential flow theory is applied to calculate the horizontal wave force acting on the caisson.The calculated results are compared with experimental data,showing the feasibility of the method.The Importance Sampling Procedure(ISP) is used to analyse the reliability of this caisson breakwater.

Hydrodynamic Performance of Multiple-Row Slotted Breakwaters

This study examines the hydrodynamic performance of multiple-row vertical slotted breakwaters. We developed a mathematical model based on an eigenfunction expansion method and a least squares technique for Stokes second-order waves. The numerical results obtained for limiting cases of double-row and triple-row walls are in good agreement with results of previous studies and experimental results. Comparisons with experimental measurements of the reflection, transmission, and dissipation coefficients （CR, Cr, and CE） for double-row walls show that the proposed mathematical model adequately reproduces most of the important features. We found that for double-row walls, the CR increases with increasing wave number, kd, and with a decreasing permeable wall part, din. The Cr follows the opposite trend. The CE slowly increases with an increasing kd for lower kd values, reaches a maximum, and then decreases again. In addition, an increasing porosity of dm would significantly decrease the CR while increasing the Cr. At lower values of kd, a decreasing porosity increases the CE, but for high values of kd, a decreasing porosity reduces the Ce. The numerical results indicate that, for triple-row walls, the effect of the arrangement of the chamber widths on hydrodynamic characteristics is not significant, except when kd〈0.5 Double-row slotted breakwaters may exhibit a good wave-absorbing performance at kd〉0.5, where by the horizontal wave force may be smaller than that of a single wall. On the other hand, the difference between double-row and triple-row vertical slotted breakwaters is marginal.

Wave Pressure Distribution over the Breast Wall of Mound Breakwater of Small Ports

In this paper, the mechanism of the interaction between the breast wall of mound breakwater and waves is expounded, then some new views and the law of variation of horizontal and vertical wave pressure over the breast wall are put forward. The results of this study have been adopted in the Specifications of Fishery Harbour Breakwater by the Ministry of Agricultures.

Numerical Modelling Investigation of Wave Interaction on Composite Berm Breakwater

The breakwaters have experienced many changes during their construction history.These changes have been considered to improve their performance,depending on their environmental conditions and applications.Numerical modelling was conducted using FLOW-3 D software.In this study,the wave overtopping from composite berm breakwater as new conceptual structure and the pressure imposed on the composite berm breakwater are considered and investigated.The results show a decrease of 84.01,70.88 and 61.42 percent of the wave overtopping in the composite berm breakwater,in comparison to the rubble mound breakwater,horizontally caisson breakwater and caisson breakwater,respectively.Also,the pressure applied to the composite berm breakwater with the pressure applied to the horizontally caisson breakwater was compared and evaluated.Composite berm breakwater compared with horizontally caisson breakwater in P1,the amount of the obtained pressure decreased by 52.09%,in P2 the amount of the obtained pressure decreased by 63.07%,in P3 decreased by 76.09%and in Pu,this pressure reduced by53.92%.For the composite berm breakwater,the impact of three types of berms,homogenous berm(Type 1),a berm consisting of armor-filter(Type 2)and multi-layer berm(Type 3)with the aim of optimizing the hydraulic responses and wave interaction on the caisson of the breakwater was examined and evaluated.In total,Type 3 will be recommended with a significant reduction in the overtopping values and maximum pressure.

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

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 exchanges.All existing empirical formulae for CTBs have been so far restricted to the water level above the bottom of the superstructure,which mainly occurs under the high tides or storm tides.However,based on recent engineering applications and experimental observations,the most severe conditions for CTBs are more likely to occur under a medium water level,because impulsive wave pressure may occur due to interactions between waves and the special chamber in CTBs.Meanwhile,during the most of construction and operation periods,the CTBs are mainly working under the medium water levels,i.e.,water levels below the bottom of the superstructure.In this study,the effects of main influence parameters on the horizontal wave force coefficient and wave transmission coefficient for open CTBs(with partially immersed side plates)under medium water levels were investigated based on a 3D numerical wave flume and corresponding empirical formulae were proposed.It is indicated that the location of the side plate related to the main caisson has significant influence on the hydrodynamic performance of CTBs.In engineering applications,the location of the side plate can be designed at b/L≤0.15 or b/L≥0.3(where b is the distance between the side plate and the front face of the main caisson and L is the incident wave length)for efficiently lowering the horizontal wave force and wave transmission.The flow mechanism of impulsive wave force on CTBs was revealed based on synchronous analyses of flow fields and pressure distribution.Through appropriate design of the height of the superstructure according to H/hD≤1.0 or H/hD≥1.5(where H is the incident wave height and hD is the distance between the still water level and the bottom of the superstructure),the likely impulsive wave pressure on the side plate can also be diminished.

大越浪下堤后建筑单体波浪冲击力计算方法

针对越浪水体对防波堤后方建筑单体冲击力缺乏理论计算公式的问题,结合地中海某油气港改扩建工程的二维物理模型试验结果,提出4种基于压力传感器测量数据的堤后单体平均波压力计算方法,并结合总力传感器结果与各种方法的计算结果进行对比分析。结果表明:越浪水体具有较高的动能,导致单个压力传感器的测量结果偏高,明显高于总力传感器结果;当试验设备受限时,可以通过均布压力传感器,取同一时刻下波压(不含负值)平均值的方式近似计算建筑单体迎浪面受到的总水平力;不同的波压平均值计算策略对总水平力的大小有影响,遍历全部测量结果计算得到的波压平均值较为合理,采取此计算策略得到的总水平力与总力传感器结果最为接近。

不开孔式与迎浪侧半开孔式水平板防波堤消浪性能比较研究

为了提升水平板防波堤的消浪性能与透水性能,设计一种迎浪侧半开孔式水平板防波堤。在不同相对板宽、潜深及波高条件下,通过物理模型试验研究不开孔式与迎浪侧半开孔式两种水平板防波堤的透射系数Kt、反射系数Kr及耗能系数Kh,系统对比两种水平板防波堤的消浪性能。结果表明,在试验参数条件下,迎浪侧半开孔式水平板防波堤的透射系数整体上小于不开孔式水平板防波堤,且两种水平板防波堤的透射系数均在相对板宽为0.166或0.212时达到最小值;两种水平板防波堤反射系数的变化趋势相近,迎浪侧半开孔式水平板防波堤的反射系数整体偏小;迎浪侧半开孔式水平板防波堤的耗散系数整体大于不开孔式水平板防波堤,在相对板宽为0.166或0.212时达到最大值。迎浪侧半开孔式水平板防波堤的消浪性能优于不开孔式水平板防波堤。

桩基双挡板透空式防波堤水平波压力试验与计算

通过物理模型试验的方法,采用不规则波研究影响两侧挡板透空式防波堤水平波压力的主要因素及其规律性。在不越浪的前提下,分别对挡板不开孔、错位开孔和不错位开孔3种结构形式进行系统的物理模型试验,并分析总结无量纲因素即挡板相对入水深度和波坦对水平波压力的影响。在上述研究成果的基础上,提出了较为实用的透空式防波堤水平波压力计算公式,对透空式防波堤的研究和设计具有较高参考和借鉴价值。

规则波作用下透空格栅板式防波堤波浪力试验研究

透空格栅板式防波堤是一种新型防波堤结构,为了促进该结构在实际工程中的应用,论文通过模型试验研究其所受波浪点压力和波浪总力的特征。试验结果表明,在规则波作用下,下层水平格栅板所受波浪点压力较上层水平格栅板大,且防波堤中前端波浪点压力分布不规律;相对板宽B/L对该防波堤所受波浪总力的影响较大,相对板间距S/h对其整体稳定性的影响次之,而相对波高H/h主要影响该防波堤的垂向受力;此外,当上层水平格栅板与静水面齐平且孔隙率相对较大时,该防波堤所受波浪总力最小,对其整体稳定性最有利。

水平斜插板透空式防波堤消波性能数值模拟

通过改进已有的防波堤模型,建立了一种新型水平斜板透空式防波堤模型。基于VOF方法建立了波浪与水平斜板防波堤相互作用的数值模型。经数值模拟研究了该新型水平斜板防波堤结构对波浪透射系数的影响,主要考虑了斜板角度、波陡、相对板间距、相对板宽和相对出水高度等因素对防波堤消波效果的影响。模拟结果显示:(1)水平斜插板透空式防波堤比水平板透空式防波堤的消波效果好。在斜插板作用下,随着斜板角度增大,透射系数逐渐增大,但增幅逐渐减小;(2)随着波陡增大,透射系数先减后增;(3)随着水平板间距增加,透射系数增大;(4)随着防波堤相对板宽的增大,透射系数逐渐减小;(5)随着防波堤出水高度增加,透射系数先减后增。结果表明,该新型结构防波堤的消波效果显著,可以很好地消减波浪,应用前景良好。

斜坡式和直墙式防波堤技术的新进展

综述第 2 7届国际海岸工程会议 (ICCE2 0 0 0 )上有关防波堤技术的新进展 ,内容包括斜坡堤护面块体的稳定性、宽肩台堤的设计标准、扭工字块体的结构失稳标准、Core- L oc块体的应用、三维波浪对混合堤的作用 ,应用预期滑动距离法设计混合堤以及水平向混合堤等。

双浮箱与不同形式板组合的浮堤消浪性能试验

对双浮箱与不同形式板组合的浮堤进行二维水槽波浪物理模型试验,探讨水平板入水深度、水平板开孔率、多孔竖直板等因素对浮式防波堤消浪性能的影响,重点分析双浮箱与多孔竖直板组合的浮堤的消浪性能和消浪机理。结果表明,对于双浮箱与水平板组合的浮堤,整体上水平板开孔时的消浪效果优于水平板不开孔时,尤其在波浪周期较长时。随着水平板入水深度的增大,浮堤的波浪透射系数明显减小、消浪效果明显改善,但整体上较双浮箱间无板时,其消浪性能仍无明显提高。与双浮箱间无板时相比,双浮箱间设置多孔竖直板时新型浮堤的波浪透射系数均减小,浮堤的消浪效果均得到明显改善。与双浮箱间无板时相比,双浮箱间设置多孔竖直板时新型浮堤的波浪反射系数均减小、波能损耗系数均增大。双浮箱间设置多孔竖直板时浮堤消浪效果改善的主要原因是双浮箱间的多孔竖直板增强了浮堤的波能损耗。

基于标准化水平残余位移的沉入式钢圆筒防波堤抗震性能研究

根据国际航运协会《港口结构抗震设计指南》、日本港口结构震害调查结果和钢圆筒结构特点,将标准化水平残余位移作为沉入式钢圆筒防波堤的抗震性能指标,同时运用振动台试验和数值模拟研究了回填砂地基防波堤的动力特性,并评估了防波堤的抗震性能。结果表明,当设计地震动为1.7 m/s2时回填砂地基防波堤处于可服役状态,设计地震动为3.2 m/s2时防波堤处于可修复状态,不满足防波堤性能等级为S的要求,建议在设计中考虑远场地震和近场地震对防波堤抗震性能的影响。振动台试验研究发现当地震波加速度峰值为3.2 m/s2时筒外回填砂由于液化导致其对防波堤的侧向力改变,防波堤试验模型发生明显的倾斜现象,建议在地基加固设计过程中重点考虑筒外回填砂。当地震波加速度峰值为1.7 m/s2和3.2 m/s2时,钢圆筒筒壁应力最大值随高度的增加均呈现减小的趋势,同时钢圆筒防波堤存在两处薄弱环节,分别位于筒底及泥面处,因此结构设计时应优先考虑。

双层水平板式防波堤消防浪性能试验研究

采用不规则波浪试验,通过探讨一定条件下双层水平板式防波堤的透射系数随相对板宽、顶板相对潜深,以及相对板间距的变化规律,研究了双层水平板式防波堤的消防浪性能。

国内外斜坡堤挡浪墙水平波浪力计算研究

本文通过研究国内外5种斜坡堤挡浪墙水平波浪力计算公式,从波浪要素、墙底高程、肩宽大小、掩护情况、斜坡堤坡度和适用范围6个方面进行对比分析,并辅以设置不同工况进行实例对比计算。结果表明国标公式因采用波浪参数较小使得波浪力计算结果偏小,且其采用固定折减系数考虑墙前掩护结构影响,对挡浪墙结构设计指导性不足;BS6349-7公式和Jensen&Bradbury公式简单,其计算结果的经验性较强;改进的Pedersen公式和Martin公式参数考虑因素较为全面,且Martin公式适用范围较广。本文研究对斜坡堤挡浪墙设计有理论指导意义。

斜坡堤挡浪墙波浪力计算方法比较

斜坡堤堤顶挡浪墙波浪力的计算,目前没有一种普遍适用的理论计算方法,文中结合实际工程的物理模型试验对目前常用的波浪力计算相关公式进行分析比较。分析结果表明,Pedersen法计算所得的波浪力与试验结果比较贴合,是目前比较稳妥的一种计算波浪力的方法,现行水文规范上波浪力计算方法得出的结果普遍偏小(相对物模试验结果),以上结果可为类似工程提供一定的参考。

淤泥质海岸防波堤工程地基监测研究

港区内软土层深厚,地基条件复杂,堤身填筑高度大,给防波堤建设带来诸多隐患.为及时反映地基稳定状况、动态指导和控制施工进度,选取典型断面开展现场监测试验,对施工过程及工后的稳定性、变形、加固效果进行现场监测与检测.结果表明:地基沉降、深层水平位移在填筑期间发展较快,填筑至堤顶后逐渐趋于稳定.监测期内地基最大沉降量为760 mm,沉降速率在10 mm/d的安全标准范围,淤泥层压缩量占地基总沉降量的86%左右;地基最大深层水平位移在深度5~14 m范围的淤泥层内,水平位移速率小于5 mm/d.地基中总的孔压值在填筑期间上升,加载结束后孔压值开始缓慢消散,呈现出良好的规律性.防波堤建设后,淤泥地基的土性指标得到了不同程度的改善,地基强度得到明显提高.