近岸波浪破碎区不规则波浪的数值模拟

基于近岸不规则波浪传播的抛物型缓坡方程和两类波浪破碎能量损耗因子,对近岸波浪破碎区不规则波浪的波高分布进行了数值模拟,并结合实验结果对数值模拟结果进行了验证分析,结果表明采用两类波浪破碎能量损耗因子所模拟的破碎区波高与实测值均吻合良好,波浪破碎能量损耗因子及波浪破碎指标对破碎区波浪波高分布影响较明显。     

基于Boussinesq方程近岸波浪演变的数值研究

首先对目前描述近岸波浪传播变形的数学模型进行了回顾与总结;对不同数学模型的特点、适用范围和发展情况进行了阐述与对比。应用基于Boussinesq方程的Coulwave模式针对几个经典实验地形进行了数值实验,数值结果和实验实测数据吻合较好。此外,分别采用不同的近岸波浪模型模拟了某渔港附近波浪的传播变形,结果表明:当考虑波浪的折射、绕射、反射联合作用时,Coulwave模式计算结果明显较缓坡方程及SWAN模型计算结果更加合理。     

基于抛物型缓坡方程模拟近岸植被区波浪传播

植被对波浪传播运动有重要影响。考虑近岸波浪在植被区传播中的折射、绕射、破碎及植被引起的波能耗损效应,基于抛物型缓坡方程建立了模拟近岸植被区波浪传播的数学模型,对模型进行了数值模拟验证,采用数值模拟试验分析了植被对波浪传播的影响。数值模拟结果表明,波浪在近岸植被区传播时,随着植被密度和植被高度的增加,波浪传播中的波高衰减增大,波能耗损增加;不同周期波浪在植被区传播中的波高衰减过程也明显不同。     

长江口水域波浪数值计算

利用高阶非线性抛物型缓坡方程对长江口水域的波浪传播变形作了推算,依据测站的资料分析数值模式中的底摩阻因子和风能输入因子对波浪传播的影响,进而确定其参数。针对不同导堤结构型式,分析了潜堤的波浪传递系数,最后对长江口二期整治工程完成后水域的波浪场作了推算。     

修正型缓坡方程的有限元模型

与缓坡方程相比,修正型缓坡方程增加了地形曲率项和坡度平方项,从而提高了数值求解的复杂性。本文将计算域划分为内域和外域,内域为水深变化区域,使用修正型缓坡方程,其中的地形曲率项和坡度平方项可用有限单元各节点的水深信息和单元插值函数表示,外域为水深恒定区,速度势满足Helmholtz方程,通过内外域的边界匹配建立有限元方程,并用高斯消去法求解。进而分别模拟了波浪传过Homma岛和圆形浅滩的变形,其结果与相关的解析解和实验数据吻合良好,证明了本文有限元模型的正确性。同时,通过与实验数据的对比也明显看出,在地形坡度较陡的情况下,修正型缓坡方程较缓坡方程具有更高的计算精度。     

近岸海浪几种数值计算模型的比较

除了统计模型，目前可用于近岸海浪计算的主要模型基本上可以分为Boussinesq方程、缓坡方程、能量平衡方程三大类。本文在对这三类模型作简要介绍的基础上，对它们用于近岸波浪计算各自存在的优缺点作了较为详细的比较，然后综合这三类模型的优点，根据目前我们所掌握的一些先进的海浪计算方法，提出一种比较实用的计算模型。     

应用SWAN模型分析航道对波浪传播的影响

应用SWAN模型,采用多向不规则波计算了秦皇岛港航道改造工程前后4个具有代表性波向的波浪场,分析了航道对工程区4个不同方向波浪传播的影响并得到了航道沿程的波高分布.改造后的秦皇岛港航道呈折线型,长为24.4 km,相应的计算区域较大,使Boussinesq模型因网格过多而难以进行计算,而缓坡方程模型在处理多向不规则波时计算过于繁琐,SWAN模型在大区域、多向不规则波情况下能够较好地解决计算问题.运用该模型计算的结果表明,秦皇岛港航道改造工程后距航道较近区域的波态发生明显的变化,但工程海区的波浪整体传播规律没有发生大的改变.     

波浪在三维圆形岛地形上的绕射研究

波浪在传播过程中遇到岛屿就会发生绕射。本文使用混合元方法对修正型缓坡方程进行了数值求解,并与KUO et al的解析解进行了比较验证。在此基础上研究了工程尺度背景下,波浪在三维圆形岛地形上的绕射,计算了不同入射波浪周期、浅滩形状参数和岛屿尺寸情况下,沿波浪传播方向断面上和岛屿岸线上的相对波高大小。计算结果表明：随着入射波周期的减小、浅滩形状参数的增大和岛屿尺寸的减小,圆形岛迎浪侧的相对波高振荡幅度、圆形岛背浪侧的相对波高大小以及岛屿岸线上的相对波高振幅和大小均随之增大。不同情况下,岛屿岸线上的相对波高最大值大多数发生在迎浪点,个别发生在迎浪点两侧20°~25°处;最小值发生在背浪点两侧30°附近。     

近岸沿岸流及污染物运动的数值模拟

基于双曲型缓坡方程和近岸浅水方程对近岸波浪斜向入射破碎所生成的沿岸流及污染物在沿岸波流作用下的运动进行了数值模拟,并对数值模拟结果进行了验证分析。数值模拟结果表明,在相近工况参数下,随着入射波高的增大,沿岸流流速和平均水面升高值均明显增大;随着岸坡坡度的增加,沿岸流流速和平均水面升高值明显增大;随着入射波浪周期的增大,平均水面升高值明显增大。在沿岸缓坡区域,由斜向入射波浪破碎所产生的沿岸流对污染物的运动起着不可忽略的影响。     

SWAN波浪模型和缓坡方程在0903号台风“莲花”波浪数值计算中的联合应用

为了提高近岸台风浪模拟的精度和效率,选取台湾海峡及其邻近海域为研究区域,以0903号台风“莲花”为例,采用大、小网格嵌套的SWAN波浪模型和抛物型近似缓坡方程联合应用的方法模拟了此台风浪场的分布特征.将验证点的计算值与浮标实测值进行对比,峰值的最大绝对偏差为0.89 m,整个模拟过程的平均绝对偏差为0.45 m,平均相对偏差在20％以内,整体模拟效果良好.为了便于分析模拟结果,选取了2009年6月20日23时、21日08时、21日14时3个典型时刻的模拟结果进行对比分析.其结果表明:(1)随着台风中心的北移,研究区域内风浪逐渐占据绝对主导地位,风与波浪的变化趋势更加吻合.21日08时泉州湾内最大风速约15 m/s,湾口的最大波高为2.8m;至21日14时台风中心逼近泉州湾口,湾内最大风速增大至20 m/s,湾口最大波高迅速增至4.4m,模拟结果与实际情况相吻合.(2)在台风中心逼近泉州祥芝中心渔港时港区受台风影响最大,但受该渔港东侧防波堤的阻挡,波浪较难进入避风水域,仅从堤头绕射进入港内,港内波高约为0.2m,港外最大波高达到2.3 m,受到东向浪侵袭时港内避风条件较好.上述结果表明,SWAN波浪模型和缓坡方程联合应用在台湾海峡及其邻近海域的台风浪数值计算中具有良好的适应性.     

Investigation of wave characteristics in a semi-enclosed bay based on SWAN model validated with buoys and ADP-observed currents

In this study, the simulating waves nearshore (SWAN) model with a locally refined curvilinear grid system was constructed to simulate waves in Jervis Bay and the neighbouring ocean of Australia, with the aim of examining the wave characteristics in an area with special topography and practical importance. This model was verified by field observations from buoys and acoustic Doppler profilers (ADPs). The model precisions were validated for both wind-generated waves and open-ocean swells. We present an approach with which to convert ADP-observed current data from near the bottom into the significant wave height. Our approach is deduced from the Fourier transform technique and the linear wave theory. The results illustrate that the location of the bay entrance is important because it allows the swells in the dominant direction to propagate into the bay despite the narrowness of the bay entrance. The wave period T p is also strongly related to the wave direction in the semi-enclosed bay. The Tp is great enough along the entire propagating direction from the bay entrance to the top of the bay, and the largest Tp appears along the north-west coast, which is the end tip of the swells’ propagation.     

Surface wave simulation during winter with sea ice in the Bohai Sea

Sea ice can attenuate wave energy significantly when waves propagate through ice covers.In this study,a third-generation wave model called simulating wave nearshore(SWAN)was advanced to include damping of wave energy due to friction in the boundary layer below the ice.With the addition of an eddy viscosity wave-ice model,the resulting new SWAN model was applied to simulate wave height in the Bohai Sea during the freezing winter.Its performance was validated with available buoy data near the ice edge,and the new model showed an improvement in accuracy because it considered the ice effect on waves.We then performed a wave hindcast for the Bohai Sea during a freezing period in the winter of 2016 that had the severest ice conditions in recent years and found that the mean significant wave height changed by approximately 16.52%.In the Liaodong Bay,where sea ice concentration is highest,the change reached 32.57%,compared with the most recent SWAN model version.The average influence of sea ice on wave height simulation was also evaluated over a five-year(2013-2017)hindcast during January and February.We found that the wave height decrease was more significant in storm conditions even the eddy viscosity wave-ice model itself showed no advantage on damping stronger waves.     

Numerical Simulation of Breaking Wave Based on Higher-Order Mild Slope Equation

The "surface roller" to simulate wave energy dissipation of wave breaking is introduced into the random wave model based on approximate parabolic mild slope equation in this paper to simulate the random wave transportation including diffraction, refraction and breaking in nearshore areas. The roller breaking random wave higher-order approximate parabolic equation model has been verified by the existing experimental data for a plane slope beach and a circular shoal, and the numerical results of random wave breaking model agree with the experimental data very well. This model can be applied to calculate random wave propagation from deep to shallow water in large areas near the shore over natu ral topography.     

Simulating typhoon waves by SWAN wave model in coastal waters of Taiwan

The SWAN wave model is typically designed for wave simulations in the near-shore region and thus is selected for evaluating its applicability on typhoon waves in the coastal waters around Taiwan Island. Numerical calculations on processes of wave heights and periods during the passages of four representative typhoons are compared with measured data from field wave stations on both east and west coasts. The results have shown that waves due to typhoons of paths 2, 3 and 4 can be reasonably simulated on east coastal waters. However, discrepancies increase for the simulated results on west coastal waters because the island's central mountains partly damage the cyclonic structures of the passing-over typhoons. It is also found that the included nested grid scheme in SWAN could improve the accuracy of simulations in coastal waters to facilitate further engineering practices.     

Numerical simulation and preliminary analysis of typhoon waves during three typhoons in the Yellow Sea and East China Sea

In this study,typhoon waves generated during three typhoons(Damrey(1210),Fung-wong(1416),and Chan-hom(1509))in the Yellow Sea and East China Sea were simulated in a simulating waves nearshore(SWAN)model,and the wind forcing was constructed by combining reanalyzed wind data with a Holland typhoon wind model.Various parameters,such as the Holland fitting parameter(B)and the maximum wind radius?,were investigated in sensitivity experiments in the Holland model that affect the wind field construction.Six different formulations were considered and the parameters determined by comparing the simulated wind results with in-situ wind measurements.The key factors affecting wave growth and dissipation processes from deep to shallow waters were studied,including wind input,whitecapping,and bottom friction.Comparison with in-situ wave measurements suggested that the KOMEN scheme(wind input exponential growth and whitecapping energy dissipation)and the JONSWAP scheme(dissipation of bottom friction)resulted in good reproduction of the significant wave height of typhoon waves.A preliminary analysis of the wave characteristics in terms of wind-sea and swell wave revealed that swell waves dominated with the distance of R to the eye of the typhoon,while wind-sea prevailed in the outer region up to six to eight times the R values despite a clear misalignment between wind and waves.The results support the hypothesis that nonlinear wave-wave interactions may play a key role in the formation of wave characteristics.     

基于SWAN模式的“灿鸿”台风浪数值模拟

以第三代海浪模式SWAN(simulating wave nearshore,近岸海浪数值模型)为基础,构建了东中国海海域波浪数值模式,并以高时间、空间分辨率的CCMP(cross calibrated multi-platform,多平台交叉校正)风场作为驱动风场进行波浪计算,模拟了1509号"灿鸿"台风的波浪过程。同时,对SWAN模式中的底摩擦参数化方案、波浪破碎参数、风能输入与白冠耗散、波-波非线性相互作用等因素对台风浪模拟的影响进行了分析,并对模式中的各影响因素给出了建议。模拟结果与浮标实测有效浪高数据(舟山朱家尖站、南麂岛站、舟山外海站、温州外海站)两者之间的偏差较小,表明本研究所建立的模式以及选择的参数合理,SWAN和CCMP风场的结合能满足海洋波浪数值模拟的需求。本研究对于台风浪数值预报具有参考意义。     

波浪谱形对不规则波数值模拟的影响

通过数值模拟分析了波浪谱形对不规则波浪数值模拟结果的影响.采用不同参数的JONSWAP谱模拟入射波要素,基于抛物型缓坡方程模拟不规则波浪的传播,分析了波浪谱形状对波浪数值模拟结果的影响.结果表明,采用抛物型缓坡方程模拟不规则波浪时,入射波浪谱形对模拟结果影响不明显;但由于模型中非线性项的影响,采用不规则波模拟的波高分布和采用规则波模拟的结果略有差别.