三维波浪在岛礁地形上破碎特性试验研究

对三维波浪在岛礁地形上的传播特性进行了物理模型试验研究。为了探究三维波浪在岛礁地形上传播的破碎指标,将岛礁地形简化为1∶5的向海坡与水平礁坪相连的物理模型。对于不同波况下的规则波、不规则波、多向波在该地形上的破碎特性进行了研究。结果表明,在该地形条件下,较大入射波高的波浪均在礁坪上发生破碎,并且随着入射波高的增大,破碎位置向来浪方向移动,破碎指标与入射波陡H_0/L_0相关,斜向波浪传播受入射角度的影响。同时,文中也给出了在该地形下波浪的破碎指标,并将三维结果与二维结果进行了对比。     

鸭式波浪能转换装置的水动力特性及效率研究

为了更加切合实际地研究鸭式波浪能转换装置的水动力特性及效率,考虑了鸭式装置可绕定轴转动以及装置的附加质量和附加阻尼,以ANSYS14.0软件为平台建立二维数值波浪水槽,对装置在不同波浪条件作用下的受力情况与运动情况进行了数值模拟与分析。结果表明:(1)在相同波高条件下,随着波浪周期的增大,装置受到的水动力力矩增大,转换效率下降,转换效率最高可达到70%;(2)在相同周期条件下,随着波高的增大,鸭式装置受到的水动力力矩也随之增加,波浪在经过装置后波高会发生衰减;(3)装置转换效率总体可维持在70%左右,但由于波峰到达装置时会有部分波浪从其顶部越过,随着波浪波高增大转换效率缓慢下降。为该装置的实际应用提供理论支持。     

波浪作用下细颗粒泥沙悬移特性的试验研究

通过9组室内水槽试验,系统分析了不同周期和波高波浪作用下粉砂质细砂的悬移特性。试验结果表明,在波浪作用下,细颗粒泥沙在水体中悬浮产生明显的三层混浊结构：近底高浓度混浊层、中部混浊层和上部低浓度混浊层。其混浊度的大小与波浪动力条件相关,波浪周期的延长和波高的增加都会使近底层悬沙浓度显著增大,悬沙浓度的波动性在近底层表现得最为突出和复杂;波浪动力条件的改变对上层水体的悬沙浓度基本不产生影响。当波浪作用停止,悬沙开始静水沉降时,近底层水体含沙浓度的变化与波浪要素的比值相关,当波浪要素的比值大于临界值时,底层含沙浓度在一定时间段内反而增加,出现浓度返起现象。     

单点系泊网衣构件波浪试验研究

采用四种网箱系泊方法,设计单点系泊网衣构件水槽波浪试验。试验构件由六种网衣和框架装配而成,试验工况是规则波,周期为0．7—2．0s,波高为50—250mm。构件在水槽中作来回周期性直线运动,当试验波浪周期较小时,构件的来回运动不明显,主要以波浪运动为主,水动力峰值大体上呈周期性均匀变化;而当周期较长、波高较高时,构件在水动力的作用下产生了与波向相反的长周期漂移运动,有较大振幅的位移、速度和加速度,诱发了水动力的最大值,水动力变化呈现峰值短周期不均匀变化、最大值长周期变化和零拉力周期变化的规律。试验结果显示,与波高参数类似,随着网衣特性系数d／a的增大,网衣构件的水动力也增大,而水动力最大值长周期、零拉力周期变化规律分别是减短和增长的。在周期1．21、1．41、1．61、1．82s情况下,网衣C构件单点系泊试验水动力最大值是固定系泊计算水动力最大值平均的1．706、1．826、2．125、2．236倍,最大达3．61倍,表明单点系泊在波浪条件下构件水动力有较大的增加。     

钱塘江古海塘水动力作用试验研究

通过古海塘原型资料调查得出古海塘现状以及存在的问题,结合历年水文资料的调研和现场水体运动形式的观测,获得荷载形式,通过波浪槽在模型比尺试验的基础上对钱塘江古海塘水动力作用进行室内模拟。试验结果验证了利用规则波模拟水动力荷载的可行性,并得出波浪对塘体的作用力受波高和波浪破碎情况的影响,波高相同时破碎点越接近海塘,破碎作用力越大;波高越大,波浪-塘体-土体相互作用越强,塘下土体中产生较大的瞬时孔隙水压力并产生孔压的累积;塘体前趾和后趾出现应力集中现象,周期1.5 s波高0.2 m时前趾压力增大后趾压力减小。     

透水珊瑚岸礁亚重力波水动力特性数值研究

基于非静压单相流模型（NHWAVE）,对随机波浪在透水珊瑚岸礁上传播过程进行了数值模拟,综合考虑入射波高、礁坪水深、谱峰周期、透水层厚度、透水层孔隙率以及颗粒的中值粒径等因素对岸礁波浪水动力特性的影响,重点分析了短波波高、低频长波波高、平均水位的沿礁变化,并与无透水层的岸礁情况进行了对比。研究表明：透水层的存在减弱了波浪在礁前斜坡的浅水变形和在礁缘附近的波浪破碎,显著降低了岸线附近的短波波高、低频长波波高以及波浪增水值,除此之外,透水层的存在会降低波浪在岸滩的最大爬高;透水层的孔隙率和颗粒的中值粒径对波浪传播变形特征的影响可忽略不计;入射波高和谱峰周期越大,岸礁透水层对短波、长波及波浪增水的影响越显著;当增大礁坪水深时,透水层对波浪的消减作用减弱;随着透水层厚度的增大,岸线附近的短波波高、长波波高和波浪增水值随之减小。     

岛礁环境波浪传播、雍水及越浪量2D模型试验研究

岛礁与大陆沿海地区的不同之处在于,它们与深水相邻,暴露于非常大的台风波浪中,并且大多数包括边缘珊瑚礁,地形变化急剧,水深由几十甚至上百米突变到1～2 m。外海波浪在礁盘边缘处发生破碎,并沿着礁盘行进,波浪形态发生重大变化,传至岛礁上的浪涌和波浪产生非线性作用,且礁坪上地形复杂,难于建立数值水槽进行研究。国内现有的海岸工程设计规范主要是针对大陆海岸,但没有针对地形复杂且水深急剧变化的深水岛礁的相关条文,而这对于确定岛礁上护岸高程、护岸距离礁盘边缘的距离等非常重要。本研究旨在研究岛礁环境中,外海波浪传递至礁盘上沿程的水动力数据,并测量距礁盘边缘400 m处的护岸越浪量,为岛礁上水工建筑物设计与应急管理提供设计参考依据。     

波浪要素对水平圆柱杆件水动力系数影响研究

通过试验研究了波浪要素对水平固定圆柱杆件水动力系数的影响。试验利用垂直杠杆原理,提取了杆件在波浪下的水平受力历时曲线,基于改造的莫里森方程,计算了不同波浪要素下的水动力系数C_D和C_M取值。定义分析了新的波高参数KH,周期参数KT和雷诺数Re对水动力系数的影响。研究表明,整体拟合法与四点拟合法获得的水动力系数在数值上差异不大。KH、KT及Re均对水动力系数的取值有较显著影响:1)随着波高KH的增大,C_D、C_M整体呈幂指数衰减,且C_M的衰减更为迅速;2)随着波周期KT的增大,C_D、C_M整体亦呈衰减趋势;3)相同波高条件下,C_M随Re数增大而增大,而C_D值相对稳定。最后给出了波浪条件下水动力系数C_D和C_M的经验计算公式。     

南沙群岛礁概化地形上拍岸浪数值模拟与统计分析

南沙群岛珊瑚岛礁众多,大多数岛礁具有向海坡陡峭、外礁坪比较平缓的特征。将南沙群岛岛礁的迎浪向地形概化为陡坡和缓坡组成的双斜坡,采用FUNWAVE-TVD模式数值模拟概化地形上的波浪,根据模拟的破碎波高分析其拍岸浪特征。对拍岸浪数值模拟结果进行比较分析,向海坡的坡度对拍岸浪影响不大,外礁坪上拍岸浪高随地形坡度增大而略有增大;向海坡和外礁坪交界位置(即坡折点)水深对拍岸浪有比较明显的影响,拍岸浪高随坡折点水深增大而减小;拍岸浪高随入射波高和波周期增大而增大。利用大量的拍岸浪数值模拟数据对国内外5种统计模型进行检验,并且基于拍岸浪数值模拟数据建立了3种南沙群岛岛礁拍岸浪统计模型,计算结果显示这些模型适用性较好。     

基于非静压模型的波浪空间聚焦研究

为研究波浪聚焦特性,分析极端波浪的产生机理,采用非静压模型通过数值模拟的方法对波浪聚焦的影响因素进行了详细研究。本文采用SWASH非静压波浪模型,模型垂向均匀分三层以保证足够的色散精度以及非线性精度来高效准确的模拟波浪在变化地形上的传播。研究发现在最大波浪未发生破碎时,波浪在半圆形凸起斜坡浅滩上传播,波浪聚焦是波高增大的最主要原因。初始kR(波数与浅滩半径乘积)值对波浪在该地形上的聚焦特性有着重要影响。初始kR越大,最大波高位置距聚焦地形坡脚的距离越远。当kR在1.4π~4.05π之间时,随着kR的减小,最大相对波高先增大后减小,当kR=2.45π时,最大相对波高达到极大值,可达2.48倍初始波高。     

Wave height transformation and set-up between a submerged permeable breakwater and a seawall

In this study,we investigated wave transformation and wave set-up between a submerged permeable breakwater and a seawall.Modified time-dependent mild-slope equations,which involve parameters of the porous medium,were used to calculate the wave height transformation and the mean water level change around a submerged breakwater.The numerical solution is verified with experimental data.The simulated results show that modulations of the wave profile and wave set-up are clearly observed between the submerged breakwater and the seawall.In contrast to cases without a seawall,the node or pseudo-node of wave height evolution can be found between the submerged breakwater and the seawall.Higher wave set-up occurs if the nodal or pseudo-nodal point appears near the submerged breakwater.We also examined the influence of the porosity and friction factor of the submerged permeable breakwater on wave transformation and set-up.     

Wave Height Transformation and Set-up Between a A Submerged Permeable Breakwater and A Seawall

In this study, we investigated wave transformation and wave set-up between a submerged permeable breakwater and a seawall. Modified time-dependent mild-slope equations, which involve parameters of the porous medium, were used to calculate the wave height transformation and the mean water level change around a submerged breakwater. The numerical solution is verified with experimental data. The simulated results show that modulations of the wave profile and wave set-up are clearly observed between the submerged breakwater and the seawall. In contrast to cases without a seawall, the node or pseudo-node of wave height evolution can be found between the submerged breakwater and the seawall. Higher wave set-up occurs if the nodal or pseudo-nodal point appears near the submerged breakwater. We also examined the influence of the porosity and friction factor of the submerged permeable breakwater on wave transformation and set-up.     

Physical modeling of the cross-shore short-term evolution of protected and unprotected beach nourishments

This paper illustrates the results of an experimental investigation (model-to-prototype length ratio equal to 12) carried out to reproduce the cross-shore evolution of nourished sandy beaches. New two-dimensional experiments were performed to study the short-term response of the cross-shore profile for both “soft” (unprotected) and “mixed” (protected by submerged breakwaters) beach fill projects. Due to the simplified reproduction of prototype conditions in a two-dimensional geometry, only cross-shore sediment transport is considered. The results are related to the immediate post-nourishment evolution and far from beach fill boundaries where long-shore gradients of long-shore sediment transport are likely to be negligible. Three different pseudo-random wave trains were generated in order to simulate both accretive and erosive conditions. A fourth wave train, characterised by time-varying incident wave spectrum was generated for the investigation of the beach response to simplified storm time evolution. Dimensionless experimental results are given in terms of wave parameters, key features of cross-shore profile evolution and sediment transport rates. Furthermore, being highly resolved in both time and space, experimental data are suitable for mathematical model validation. It was observed that submerged breakwater switches erosive conditions to slightly accretive, at least within the tested experimental range.     

柔性水囊潜堤消波特性的溃坝水槽试验研究

柔性水囊潜堤由橡胶制成,内部充水,具有结构简单、造价低廉等优点,能较好满足人工岛、跨海桥梁、海洋平台等基础设施建设工程对简单便携、拆装方便的临时防波堤的需求。为了探究柔性水囊潜堤的消波特性,在溃坝水槽内开展溃坝波与半圆柱形柔性水囊潜堤相互作用的试验研究,重点探究柔性水囊潜堤与溃坝波相互作用过程中水位变化特性,并与半圆柱刚性潜堤的性能进行比较;同时分析柔性水囊潜堤内部初始水压和浸没深度等参数对其消波性能的影响。结果表明：柔性水囊潜堤能够用作临时防波堤来衰减波浪;与半圆柱刚性潜堤相比,柔性水囊潜堤在降低溃坝波无量纲最大水位、提高消波性能方面更具优势;内部初始水压是影响柔性水囊潜堤消波性能的重要因素,适当降低内部初始水压,有利于增强柔性潜堤的变形程度,进而增加波能耗散,可获得更好的消波效果;而增加浸没深度即潜深,会使得柔性水囊潜堤对溃坝波的影响程度降低,消波效果减弱。     

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...     

波浪在Jarlan型开孔潜堤上的运动

The wave motion over a submerged Jarlan-type breakwater consisting of a perforated front wall and a solid rear wall was investigated analytically and experimentally. An analytical solution was developed using matched eigenfunction expansions. The analytical solution was confirmed by previously known solutions for single and double submerged solid vertical plates, a multidomain boundary element method solution, and experimental data. The calculated results by the analytical solution showed that compared with double submerged vertical plates, the submerged Jarlan-type perforated breakwater had better wave-absorbing performance and lower wave forces. For engineering designs, the optimum values of the front wall porosity, relative submerged depth of the breakwater, and relative chamber width between front and rear walls were 0.1–0.2, 0.1–0.2, and 0.3–0.4, respectively. Interchanging the perforated front wall and solid rear wall may have no effect on the transmission coefficient. However, the present breakwater with a seaside perforated wall had a lower reflection coefficient.     

潜堤上破碎波浪传播变形的数值模型及其验证

为模拟潜堤上破碎波浪传播时产生能量的耗散这一特性,在改进的具有四阶色散的Boussinesq水波方程中中入二阶紊动粘性项,建立了考虑波浪破碎的水波数学模型.在非交错网格下建立了有限差分数值模型,并利用三阶Adams-Bash forth格式预报、四阶Adams-Mouton格式校正对数值模型进行求解.通过数值试验,模拟...     

Numerical simulation of nonlinear dispersive waves propagating over a submerged bar by IB–VOF model

It is a good test for a numerical model to simulate progressive waves propagating over a submerged bar with a relatively high ratio of slopes. In this paper, the combined IB–VOF model is used to predict nonlinear dispersive waves propagating over a submerged bar with both slopes of 1:2. The predicted free surface elevations are compared with the experimental data and numerical results presented by other researchers. The comparison shows that the IB–VOF model is able to provide satisfactory wave profiles in the shallow water with strong nonlinear effects and in the wave transmitted region with strong wave dispersion in particular. Moreover, the wave evolution behind the submerged bar is described in detail, including the spatial wave profile modulation, spectral analysis of the time-series waves, flow velocity and pressure fields, and kinetic energy distribution. The effect of fluid viscosity on the numerical simulations is also studied, and it is found that the effect on the wave evolution considered in this paper is not significant. Finally, the hydrodynamic force acting on the bar is calculated using the IB–VOF model.     

A Finite Element Solution of Wave Forces on Submerged Horizontal Circular Cylinders

In this paper, a numerical model is established for estimating the wave forces on a submerged horizontal circular cylinder. For predicting the wave motion, a set of two-dimensional Navier-Stokes equations is solved numerically with a finite element method. In order to track the moving non-linear wave surface boundary, the Navier-Stokes equations are discretized in a moving mesh system. After each computational time step, the mesh is modified according to the changed wave surface boundary. In order to stabilize the numerical procedure, a three-step finite element method is applied in the time integration. The water sloshing in a tank and wave propagation over a submerged bar are simulated for the first time to validate the present model. The computational results agree well with the analytical solution and the experimental data.Finally, the model is applied to the simulation of interaction between waves and a submerged horizontal circular cylinder.The effects of the KC number and the cylinder depth on the wave forces are studied.     

风机基础TLP平台在波浪中运动性能的CFD数值分析

随着海上风能的开发向深水发展,支撑风机的载体平台越来越受到关注。在经济性与安全性、稳定性的多重要求下,张力腿平台（TLP）在海洋风能资源的开发中体现出了重要地位。采用基于开源平台OpenFOAM开发的计算流体动力学（CFD）水动力学求解器naoe-FOAM-SJTU对一座处于中等水深下的风机基础水下TLP（STLP）的运动响应进行了数值模拟与研究。文中使用弹簧锚链模型模拟STLP的垂向系泊锁链系统,模拟该平台在不同波浪环境下的运动响应情况。首先将STLP单自由度自由衰减CFD模拟结果与已有全耦合时域分析结果进行对比,验证了naoe-FOAM-SJTU求解器及使用弹簧模型模拟STLP系泊系统的准确性与可靠性。随后在考虑非线性波浪载荷的情况下研究极端海况下与一般作业海况下STLP的运动响应情况,计算工况中的风机基础所受弯矩及锚链受力情况,并详细展示流场、速度场信息,分析高阶波浪成分、不同海况等条件对于STLP运动性能的影响。研究结果表明,TLP在中等水深中具有良好的运动性能,naoe-FOAM-SJTU求解器可以有效模拟水中生产平台在波浪环境下的水动力问题,并可以对整个流场进行可视化展示与分析。