时域模型FUNWAVE与SWASH的对比研究

本文采用Berkhoff为验证缓坡方程的不同计算方法可信度所使用的地形,对基于Boussinesq方程的FUNWAVE和基于NS方程的SWASH两种时域模型进行了比较分析,通过与实测数据对比,结果显示两种模型都能达到较好的精度,整体上FUNWAVE略好于SWASH,但基于相同的模型设置,SWASH运行速度远远快于FUNWAVE。综合考虑两种模型的精度与运行速度,SWASH模型被认为更具实用性。

Different responses of two adjacent artificial beaches to Typhoon Hato in Zhuhai,China

Major differences in beach erosion between two neighboring artificial beaches Xiangluwan Beach(XL beach)and Meiliwan Beach(ML beach)in Zhuhai,China,were studied after Super Typhoon Hato.In this study,a fully nonlinear Boussinesq wave model(FUNWAVE)-Total Variation Diminishing(TVD)was used to distinguish the main impact factors,their relative contributions,and the hydrodynamic mechanisms underlying the different beach responses.Results show that compared to the ML beach,the main reason for the relatively weak erosion on Xiangluwan(XL)beach was the smaller beach berm height(accounting for approximately 75.9%of the erosion response).Regarding the beach with a higher berm,the stronger wave-induced undertow flow,along with the higher sediment concentration,led to a higher offshore sediment transport flux,resulting in more severe erosion relative to the beach with a smaller berm height.The second most important reason explaining the weak erosion on XL beach was the absence of seawalls(accounting for approximately 17.9%of the erosion response).Wave reflection induced by the seawall could cause higher suspended sediment concentration,resulting in a toe scouring near the seawall.The offshore submerged breakwater protected XL beach slightly(accounting for approximately 6.1%of the erosion response).Due to the higher water level induced by storm surge,most of the wave energy could penetrate through the submerged breakwater.The effect of the larger berm width of XL beach was negligible.Compared to the beach with a larger berm width,the erosion/deposition regions in the beach with a narrower berm width showed shoreward migration,without significant changes in the erosion/deposition extent.Despite of this,the larger berm width could reduce the wave energy reaching the shoreline.This study of the storm stability of artificial beaches may be applied to beach restoration design.

岛礁地形上拍岸浪的数值模拟研究

近年来,越来越多的海岸工程与军事活动在岛礁上展开。研究岛礁地形上拍岸浪的传播特征具有重要的指导作用和现实意义。在对波浪破碎的研究中,数值模拟方法以其经济可行、操作性强的优势而得到了广泛的应用。本文采用基于完全非线性Boussinesq方程的数值模型FUNWAVE-TVD模式,对岛礁地形上拍岸浪的传播过程进行模拟,并将模拟结果与实验室数据进行对比。在此基础上,通过修改岛礁前坡坡度,分析了不同坡度下波浪的传播变化特征。结果表明,FUNWAVE-TVD模式能够较为准确地模拟岛礁地形上拍岸浪的非线性作用以及破碎现象。波浪破碎位置随岛礁前坡坡度的减小而前移。

Numerical simulations of rip currents off arc-shaped coastlines

The rip currents induced by waves off arc-shaped coastlines are seriously harmful to humans, but understanding of their characteristics is lacking. In this study, the FUNWAVE model was used to calculate the wave-induced currents in the Haller experiment and the ideal arc-shaped coast similar to Sanya Dadonghai, Hainan Province,China. The results showed that the FUNWAVE model has considerable ability to simulate the rip currents, and it was used to further simulate rip currents off arc-shaped coastlines to investigate their characteristics. The rip currents were found to be stronger as the curvature of arc-shaped coastline increased. Coastal beach slope exerts a significant influence on rip currents; in particular, an overly steep or overly mild slope is not conducive to creating rip currents. Furthermore, the rip currents were found to become weaker as the size of arc-shaped coast decreased. When the height and period of waves increase, the strength of rip currents also increases, and, in some cases, wave heights of 0.4 m may produce dangerous rip currents.

Statistical Analyses of Wave Height Distribution for Multidirectional Irregular Waves over A Sloping Bottom

The main objective of this paper is to examine the influences of both the principal wave direction and the directional spreading parameter of the wave energy on the wave height evolution of multidirectional irregular waves over an impermeable sloping bottom and to propose an improved wave height distribution model based on an existing classical formula.The numerical model FUNWAVE 2.0,based on a fully nonlinear Boussinesq equation,is employed to simulate the propagation of multidirectional irregular waves over the sloping bottom.Comparisons of wave heights derived from wave trains with various principal wave directions and different directional spreading parameters are conducted.Results show that both the principal wave direction and the wave directional spread have significant influences on the wave height evolution on a varying coastal topography.The shoaling effect for the wave height is obviously weakened with the increase of the principal wave direction and with the decrease of the directional spreading parameter.With the simulated data,the classical Klopman wave height distribution model is improved by considering the influences of both factors.It is found that the improved model performs better in describing the wave height distribution for the multidirectional irregular waves in shallow water.

近岸沙坝海滩裂流数值模拟与动力学分析

裂流是海滨旅游区的重要安全隐患,世界范围内80%以上的海滩救援事件都与裂流有关。本文基于FUNWAVE非线性波浪分辨模型,对近岸常见沙坝海滩裂流灾害进行数值模拟,给出裂流过程中的平均海平面水位、均方根波高、涡流场和裂流流场的分布特征。设计敏感实验,研究了入射波高、波角和潮汐水位大小对裂流灾害的影响。入射波高增加,裂流风险增大,低潮汐水位,对应的裂流强度在增加。入射波角的增加,能够使离岸流速分量减少,使裂流风险减少。通过计算不同时间间隔的裂流平均流速,研究不同时间平均对裂流流速的影响,说明利用波浪平均模型,得到较大时间间隔的裂流平均流速,通常能够低估裂流流速,计算的裂流风险不够准确,而利用FUNWAVE波浪分辨模型,能够精确地模拟计算裂流瞬时流速和流速阈值,适合对裂流灾害进行模拟和评价。