基于水槽实验的近岸波浪破碎计算研究

将前人波浪破碎计算及判定公式进行汇总、整理并分成3类;同时,为了对选取公式进行比较,文还将上述公式分为两类破碎波高计算模型,一类是直接计算模型;另一类是联立拍岸浪波高计算模型与破碎判据,建立的间接计算模型。在此基础上,结合实验数据,对破碎波高和破碎指标进行误差分析得出,间接计算模型中,Goda提出的破碎判据效果最好,为下一步拍岸浪精细化预报以及其区域计算模型的建立提供参考。     

基于波形不对称性的波浪破碎指标

为了探寻波浪破碎与波形不对称性的关系,通过对1/200缓坡上波浪破碎实验研究结果的进一步分析,运用最小二乘法,拟合了波形不对称性参数与相对水深的关系,以及用波形不对称性参数表示的波浪破碎指标表达式。所得规则波的结果与Kjeldsen的深水波结果相同,而不规则波的结果比规则波的小。研究还表明,这一破碎指标与相对水深有关系,随着水深变浅,指标值增大。     

破碎波作用下圆端形桥墩受力特性数值模拟

当波浪由外海向跨海桥梁所在的近岸海域传播时,随着水深急剧变浅,波浪会发生破碎。强非线性的破碎波会给桥墩结构带来极大冲击作用。基于计算流体力学(CFD)数值软件Flow-3D建立三维数值水槽,造波边界设为斯托克斯五阶波。通过在数值水槽中建立逐渐浅化的三维地形,采用k-ω湍流模型求解雷诺平均N-S(RANS)方程,模拟破碎波冲击桥墩。与前人水槽试验及数值模拟结果进行比对,验证数值水槽的有效性。采用验证过的数值水槽,研究了不同入射波高和周期下的破碎波浪特性,计算了不同长宽比圆端形桥墩在不同入射波高的破碎波作用下受力和流场变化,讨论了最大压强作用点、准静态力和冲击力随桥墩长宽比的变化规律。研究表明:与前人试验和数值模拟相比,所建立的数值水槽具有较高精度;圆端形桥墩破波力随桥墩长宽比增大,先增大后趋于稳定,破波力峰值随着入射波高的增大而增大,同时,圆端形桥墩破波力峰值主要由冲击力控制。进行跨海桥梁圆端形桥墩设计时,应重点关注桥墩长宽比和破碎波冲击力的影响。     

斜坡上波浪破碎与越浪非静压数值模拟

为合理确定防浪建筑物的越浪量,基于含非静水压力梯度项的非线性浅水方程建立了近岸波浪越浪数值模型。通过采用域内造波、消波并结合波前静压假定的破碎模型,模拟了规则波和不规则波在斜坡上的波浪传播变形,并在此基础上进行了越浪量数值计算。数值计算结果与物理模型实验结果表明,非静压模型可合理地描述波浪破碎点位置、破碎后的波高、增减水以及斜坡上的堤后越浪量。数值模型具有较高的计算精度和计算效率,可为实际工程防浪建筑物越浪以及堤顶高程的设计提供一种新的数值研究手段。     

可渗透海床单桩孤立波破碎波浪力数值研究

当波浪传播至近岸浅水区时易发生破碎,波浪破碎后水体直接拍击单桩结构,其波浪作用力显著增大,可能导致结构失稳破坏。首先建立包括斜坡海床的数值波浪水槽,并与已有研究进行对比验证。进而开展考虑斜坡海床可渗透性的孤立波数值模拟,分析孤立波传播与浅水化破碎特征,着重研究竖直单桩上破碎波浪力的特性,及其与单桩位置、海床渗透率的关联性。数值研究发现:对于低渗透率海床,随着单桩位置由深水向岸线位置变动,其所受波浪力先增后减,所受波浪力最大的桩体位置随海床渗透率增加而从波浪破碎点前方移动至破碎点后1D处,而在高渗透率海床上不同位置处桩体所受波浪力均较小;随海床渗透率等梯度增加,海床消波作用逐渐增强,波浪破碎进程延缓,波浪破碎点向岸线方向加速移动,单桩上破碎波浪力呈整体下降趋势,但可能因波浪破碎点的位置变动导致部分位置桩体所受波浪力异常增大。     

一种基本Boussinesq方程的近岸区破碎波模型

基于文献「１」Ｂｏｓｓｉｎｅｓｑ方程的近岸区破碎波模型基础,将数值模型中的波高衰减规律由假设改进为Ｄａｌｌｙ的解析公式,使近岸区破碎波模型的应用性更强。并将数值模型计算结果与现场实验资料进行对比,取得了满意的结果。     

完全非线性波浪破碎模型沿岸流数值模拟

探讨一种基于完全非线性Boussinesq方程的波浪破碎模型在沿岸流计算中的应用问题。针对控制方程中的完全非线性项对沿岸流成长过程的影响进行了深入讨论。数学模型计算结果表明,完全非线性项有使平均流局部化的作用;通过数模实验还发现,垂向高阶涡度项可以有效抑制破波区外回流;运用Visser的实验室沿岸流实测资料从沿岸流速度、波高和平均水位几方面对所提模型进行了验证,并给出了紊动参数的计算结果。     

Experimental study on suspended sediment concentration and its vertical distribution under spilling breaking wave actions in silty coast

In this paper,flume experiments are focused on sediment transport inside and outside the surf zone.According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump,formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves.Assuming that the sediment diffusion coefficient,which is related with energy dissipation,is proportional to water depth,formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves,and the prediction shows a good agreement with the measurement.     

基于破碎临界区的新型拍岸浪统计计算模型研究

When waves propagate from deep water to shallow water, wave heights and steepness increase and then waves roll back and break. This phenomenon is called surf. Currently, the present statistical calcula...     

斜坡平台波浪破碎数值模拟

波浪在斜坡地形上破碎,破波后稳定波高多采用物理模型试验方法进行研究,利用近岸波浪传播变形的抛物型缓坡方程和波能流平衡方程,导出了适用于斜坡上波浪破碎的数值模拟方法。首先根据波能流平衡方程和缓坡方程基本型式分析波浪在破波带内的波能变化和衰减率,推导了波浪传播模型中波能衰减因子和破波能量流衰减因子之间的关系;其次,利用陡坡地形上的高阶抛物型缓坡方程建立了波浪传播和波浪破碎数学模型;最后,根据物理模型试验实测数据对数值模拟的效果进行验证。数值计算与试验资料比较表明,该模型可以较好地模拟斜坡地形的波浪传播波高变化。     

Numerical simulation of solitary wave propagation based on MPS method

The concept of candidate particle set is introduced in the MPS gridless numerical method to generate neighboring particle set matrix, which can reduce the CPU time to 1/11 of that before introduction. The Bi-CGSTAB (bi-conjugate gradient stabilized) algorithm is applied to solving the Poisson pressure equation, by which the solving speed is significantly accelerated. The process of solitary waves propagating over a numerical flume and interacting with a vertical wall is simulated. The simulated results of water surface elevation are in good agreement with the analytical solution as well as the measured data. The predicted maximum values of the run-up of solitary waves with various relative incident wave heights agree well with the measured results.     

基于格子Boltzmann方法的斜坡堤越浪数值模拟研究

准确确定越浪量对于斜坡堤设计有重要意义。利用格子Boltzmann方法(LBM),并采用主动吸收式速度入口造波、出流边界消波、VOF方法追踪自由表面以及静态Smagorinsky模型模拟紊流运动,建立二维数值波浪水槽,对光滑斜坡堤上规则波与不规则波越浪进行数值模拟。模拟结果与试验值及其他数值模型结果比较表明,二维LBM数值波浪水槽具有模拟斜坡堤越浪的能力,但对于破碎较为剧烈的越浪过程模拟,该模型还存在一定的不足,未来可从提高自由表面模型精度等方面进一步改善其性能。     

Effects of wave breaking on wave statistics for deep-water random wave train

The experimental studies of the breaking effects on wave statistics for deep-water random waves are presented. It is especially focused on the behavior of kurtosis of surface elevations due to wave breaking. Wave breaking suppresses the maximum limit of kurtosis of the surface elevation, although skewness depends on characteristic wave steepness. The mean instantaneous wave steepness of breaking waves defined using the zero-down-crossing method was much lower than expected from the Stokes waves.     

Determining the onset and strength of unforced wave breaking in a numerical wave tank

A numerical wave tank is used to investigate the onset and strength of unforced wave breaking, and the waves have three types of initial spectra： constant amplitude spectrum, constant steepness spectrum and Pierson-Moscowitz spectrum. Numerical tests are performed to validate the model results. Then, the onset of wave breaking is discussed with geometric, kinematic, and dynamic breaking criteria. The strength of wave breaking, which is always characterized by the fractional energy loss and breaking strength coefficient, is studied for different spectra. The results show how the energy growth rate is better than the initial wave steepness on estimating the fractional energy losses as well as breaking strength coefficient.     

海浪破碎对北太平洋海表面温度模拟的影响

基于海浪模式WAVEWATCH Ⅲ模拟北太平洋海浪要素,结合NDBC浮标资料进行验证,发现模拟出的有效波高与浮标测量值具有很好的一致性。基于改进型白冠覆盖率耗散模型,利用海浪模式模拟出的有效波高、有效波周期和摩擦速度等海浪要素计算出单位面积水柱内因海浪破碎产生的湍动能通量。通过改变环流模式sbPOM湍动能方程的上边界条件,引入海浪破碎产生的湍动能通量,并探究海浪破碎对北太平洋海表面温度模拟的影响。研究表明,由于海浪破碎的引入,环流模式sbPOM对北太平洋海表面温度模拟的准确程度得到提升,这为大气模式提供一个准确的北太平洋下边界条件具有重要意义。     

近破波作用下沉箱式防波堤运动特性的模型实验研究

对近破波作用下沉箱式防波堤的运动特性进行了模型实验研究。实验中测量了沉箱模型与基床的摩擦系数、基床刚度和阻尼系数;不同水位情况下作用于沉箱模型上的近破波波压力时程;近破波作用下沉箱模型的位移和转角响应时程等,并与数学模型计算结果进行了比较分析。实验结果表明,若沉箱的滑移力大于沉箱与基床间的摩擦力,在连续波浪作用下,沉箱将连续出现间歇式滑移运动,数学模型可较好地模拟这一运动过程。     

The BCI criterion for the initiation of breaking process in Boussinesq-type equations wave models

The Breaking Celerity Index (BCI) is proposed as a new wave breaking criterion for Boussinesq-type equations wave propagation models (BTE).The BCI effectiveness in determining the breaking initiation location has been verified against data from different experimental investigations conducted with incident regular and irregular waves propagating along uniform slope [Utku, M. (1999). “The Relative Trough Froude Number. A New Criteria for Wave Breaking”. Ph.D. Dissertation, Dept. of Civil and Enviromental Engineering, Old Dominion University, Norfolk, VA; Gonsalves Veloso dos Reis, M.T.L. (1992). “Characteristics of waves in the surf zone”. MS Thesis, Department of Civil Engineering, University of Liverpool., Liverpool; Lara, J.L., Losada, I.J., and Liu, P.L.-F. (2006). “Breaking waves over a mild gravel slope: experimental and numerical analysis”. Journal of Geophysical Research, VOL 111, C11019] and barred beaches [Tomasicchio, G.R., and Sancho, F. (2002). “On wave induced undertow at a barred beach”. Proceedings of 28th International Conference on Coastal Engineering, ASCE, New York, 557–569]. The considered experiments were carried out in small-scale and large-scale facilities. In addition, one set of data has been obtained by the use of the COBRAS model based upon the Reynolds Averaged Navier Stokes (RANS) equations [Liu, P.L.-F., Lin, P., Hsu, T., Chang, K., Losada, I.J., Vidal, C., and Sakakiyama, T. (2000). “A Reynolds averaged Navier–Stokes equation model for nonlinear water wave and structure interactions”. Proceedings of Coastal Structures ‘99, Balkema, Rotterdam, 169–174; Losada, I.J., Lara, J.L., and Liu, P.L.-F. (2005). “Numerical simulation based on a RANS model of wave groups on an impermeable slope”. Proceedings of Fifth International Symposium WAVES 2005, Madrid].Numerical simulations have been performed with the 1D-FUNWAVE model [Kirby, J.T., Wei, G., Chen, Q., Kennedy, A.B., and Dalrymple, R.A. (1998). “FUNWAVE 1.0 Fully Nonlinear Boussinesq Wave Model Documentation and User's Manual”. Research Report No CACR-98-06, Center for Applied Coastal Research, University of Delaware, Newark]. With regard to the adopted experimental conditions, the breaking location has been calculated for different trigger mechanisms [Zelt, J.A. (1991). “The run-up of nonbreaking and breaking solitary waves”. Coastal Engineering, 15, 205–246; Kennedy, A.B., Chen, Q., Kirby, J.T., and Dalrymple, R.A. (2000). “Boussinesq modeling of wave transformation, breaking and run-up. I: 1D”. Journal of Waterway, Port, Coastal and Ocean Engineering, 126, 39–47; Utku, M., and Basco, D.R. (2002). “A new criteria for wave breaking based on the Relative Trough Froude Number”. Proceedings of 28th International Conference on Coastal Engineering, ASCE, New York, 258–268] including the proposed BCI.The calculations have shown that BCI gives a better agreement with the physical data with respect to the other trigger criteria, both for spilling and plunging breaking events, with a not negligible reduction of the calculation time.     

规则波在浅水中运动及破碎的数值计算

利用一维Boussinesq方程描述了在浅水中的波浪运动以及破碎情况。在方程中引入了表面翻滚的概念，认为翻滚的水体是以波速运动的，翻滚的作用表现在水平速度的垂直分布上，产生了附加迁移动量项。通过对Airy波在浅水中运动以及破碎情况的研究，得出的一些结论与Schaeffer和合田的成果吻合良好。     

不同破碎波气液混合区发展特征及其运动特性研究

了解波浪破碎速度场的分布特性对于波浪破碎物理机制的研究极为重要,同时,对比研究不同类型破碎产生的气液混合区的演化特征有利于波浪白冠覆盖率模型的完善。在实验室水槽,生成了深水临界波、单次崩破波和单次卷破波,采用图像测速技术获取了波浪破碎图像、波面下水体和气液混合区速度场。结果表明,崩破波的水平向速度u和垂直向速度v在波峰前和波峰后的分布极为不对称,其水平向最大速度umax并不位于峰顶,而是在主导波峰前0.7$\eta_{\max} $处;卷破波的umax出现在波峰峰顶前端极小的区域内,且该区域与周围区域的速度梯度极大。崩破波和卷破波生成的气液混合区发展特征也存在差异：崩破波的umax值大、影响区域长、混合区厚度较小、各区域影响时间短;而卷破波的各项特征参数与崩破波形成对比。     

韦帕台风对连云港典型水域波能损耗及悬沙含沙量影响研究

旨在建立淤泥质海岸条件下波能功率沿程损耗和水体悬沙垂向悬浮功率之间的时间对应关系。通过韦帕台风时期连云港波浪数学模型,求解了测点处波能功率沿程损耗的变化过程。结合实测资料进行分析后认为,该过程与波高过程存在相位差,同时与实测水体悬沙含沙量变化过程对应关系较好。结合以往研究成果,说明利用波能功率衰减变化推求淤泥质海岸风天条件下的水体含沙量变化可以同时满足空间和时间上对应关系。还分析了底部摩阻损耗与底部含沙量之间的对应关系,两者在时空分布上也较为吻合。通过韦帕台风实测资料和数学模型结果,推求出波能功率沿程损耗与悬沙垂向悬浮功率之间的转化因子为0.3。