长峰不规则波数值模拟的相关问题

针对波浪数值水池研究现状,提出了长峰不规则波数值波浪水池研究亟待解决的3个问题:海浪谱的拓展、波能衰减机理讨论及长峰不规则波数值模拟精度评价标准.基于黏性数值波浪水池技术,以文氏海浪谱为目标谱,对深水长峰不规则波进行了数值模拟;分析了数值模拟中波能衰减的主要原因,并提出了基于优化网格生成和离散格式的减小衰减的方法;根据《水面船模耐波性试验规程》对数值模拟结果进行了误差计算,并提出了适用于不规则波数值模拟评价标准的建议.     

近岛礁有理分式波浪谱研究

近岛礁波浪具有较强非线性和较弱色散性,体现在波浪谱上就是自相似和长尾。这两个特点可以用有理分式来描述。该文据此提出了近岛礁波浪有理分式形式的波浪谱,该谱型还可以描述双峰谱。通过南海某典型岛礁实测波浪数据的分析,给出了20组实测数据的有理分式波浪谱。通过与常见的波浪谱对比分析,可以看到有理分式波浪谱能够更准确地揭示出近岛礁波浪的特性。     

海上风电机组基础浪致疲劳分析

给出了海上风电机组基础波浪荷载导致的疲劳损伤计算方法。基于随机波浪理论,依据海浪谱将随机波浪转换为一系列线性波的组合,由Morison方程计算得到波浪荷载并进行线性化。根据线性波浪荷载作用下结构的动力分析,求得结构响应并计算得到频域范围内的结构应力传递函数。根据海浪谱和应力传递函数,进而得到结构的热点应力谱。由某海域的海况分布,依据Miner线性累计损伤准则,通过假定结构长期热点应力分布为短期Rayleigh分布的组合,计算得到结构在设计周期内的累计疲劳损伤。以某单桩基础为例,验证了计算方法的可行性。计算方法对海上风电机组基础的浪致疲劳设计具有参考价值。     

室内模型试验中波浪绕射的多波向合成

用频谱和单一方向的不规则波来分析海浪或在试验室内进行模拟,是目前的一种倾向。实践证明,仅用频谱已不能充分描述海浪的特性,同样,用单一方向的不规则波进行港口掩护试验,已不能确切反映港口的实际波况。波浪绕射很大程度上取决于入射波的方向。而且用规则波的绕射结果进行工程设计,将是偏于不利的。因此,在波浪绕射模型试验中需应用方向谱。本文通过单一方向不规则波乃至规则波,进行波浪绕射的多波向合成,而达到方向谱波的实际效果。这对合理设计港口工程,有着现实意义。     

孤立波中淹没圆盘的波浪力实验研究

在近海海啸波水池中进行了孤立波作用下淹没圆盘的波浪力实验,建立了一套具有较大刚度的淹没圆盘波浪力多分量同步测量系统,获得了不同水深和淹没深度下波面和波浪载荷随时间的变化历程。针对波面不破碎工况,当孤立波经过完全淹没圆盘时,通过分析垂向力、水平力和倾覆力矩的时间序列,阐述了孤立波推进过程中圆盘上下表面的压力分布特征及其对波浪力的影响规律。依据波浪力极值的测量数据,给出不同相对波高条件下水平力系数、垂向力系数和倾覆力矩系数的实验结果,揭示了其变化规律。     

近岛礁波浪谱演化逆问题研究

波浪从深水区传播到岛礁附近,受海底地形影响将发生一系列复杂的浅水变形,且根据已有现场观测资料发现其波浪谱型与目前常用的海浪谱存在明显的差异。该文基于随机波浪理论,通过近岛礁波浪谱的演化分析,解决了在模型试验中如何生成符合岛礁附近特殊波浪谱型这一波浪演化的逆问题,并通过近岛礁水池模型试验数据验证了该方法的准确性和可行性,为后续模型试验中近岛礁波浪演化的精确模拟奠定了基础。     

波浪群性作用下系泊船运动响应和统计特征值分析

码头前系泊船的运动响应与缆绳张力对于码头的运营安全至关重要。波群对系泊浮体波浪载荷特性不同于普通的随机波浪,具有一定的特殊性。该文对两种模拟波群方法进行了讨论,分析了两种模拟波群方法的特点以及群性与波浪统计特征值之间的关系。在此基础上开展了群性波浪作用下系泊船的运动响应研究,得出了谱峰因子?、群高参数GFH和群长参数GLF与波浪特征波高的变化规律。     

气旋生浪的数值模拟研究及其特征分析

利用Holland模型、Jelesnianski模型构造飓风风场,并针对快速移行气旋其风场不对称性明显的特征构造一种基于实测数据的风场,驱动第三代海浪模式WAVE WATCHⅢ,对飓风Juan影响下北大西洋的海浪进行数值模拟。通过对比试验结果与观测数据的误差,比较3种方法对于合成高速移行飓风风场的适用性,并选择最优模拟结果对海浪组成特征进行分析。结果表明:基于实测数据的合成风场与真实风场最接近,海浪模拟效果最优;飓风中心海域有大片的风浪大值区,风浪4 m波高等值线内基本无涌浪,涌浪主要分布在风浪大值区外围左侧海域;风浪波高比涌浪波高大,涌浪影响范围广。     

《OSB-1》近海遥测波浪浮标系统

收集近海波浪资料对上海的围垦工程,海塘防汛工程、长江口整治以及浦东新区的建设等,都无疑是一项重要的基础工作。由于人工观测波浪技术手段落后,精度差,特别无法收集强台风浪的实测资料,由上海市水利局、水文总站与中科院南海所共同研制     

不规则波浅水变形计算

本文在前人研究的基础上,收集了我国近海地区的一些海浪谱,根据这些波谱的特点,考虑到引起波浪浅水变形的波浪折射、浅水效应及底摩擦损耗等因素,以汕头港防沙堤设计波要索的计算为实例,利用合成迭加法,进行波浪浅水变形计算。     

Case study on wave-current interaction and its effects on ship navigation

The East China Sea, where both the strong Kuroshio Current and powerful low pressures exist, is an inevitable ocean area for various ships sailing between Japan and other Asian and European countries. The safety and economics of such shipping behaviors are often affected by the strong dynamics of the environmental matrix. The wave conditions are usually significant under high ocean winds, leading to interaction between waves and currents. In this study, the third generation wave model SWAN are used to study the wave propagation and wave-current interaction, following by its effects on the ship navigation discussed. Significant interaction between the strong Kuroshio Current and high ocean waves as well as its effects on ship safety have been found by calculations of certain wave parameters, such as significant wave height(SWH), average wave period(AWP), mean wave direction(MWD), wave length(WLEN), frequency and directional spreading.     

Mathematical model of wave transformation over radial sand ridge field on continental shelf of South Yellow Sea

According to a deformed mild-slope equation derived by Guang-wen Hong and an enhanced numerical method,a wave refraction-diffraction nonlinear mathematical model that takes tidal level change and the high-order bathymetry factor into account has been developed.The deformed mild-slope equation is used to eliminate the restriction of wave length on calculation steps.Using the hard disk to record data during the calculation process,the enhanced numerical method can save computer memory space to a certain extent,so that a large-scale sea area can be calculated with high-resolution grids.This model was applied to wave field integral calculation over a radial sand ridge field in the South Yellow Sea.The results demonstrate some features of the wave field:(1)the wave-height contour lines are arc-shaped near the shore;(2)waves break many times when they propagate toward the shore;(3)wave field characteristics on the northern and southern sides of Huangshayang are different;and(4)the characteristics of wave distribution match the terrain features.The application of this model in the region of the radial sand ridge field suggests that it is a feasible way to analyze wave refraction-diffraction effects under natural sea conditions.     

URANS simulations of ship motion responses in long-crest irregular waves

In this paper, numerical prediction of ship motion responses in long-crest irregular waves by the URANS-VOF method is presented. A white noise spectrum is applied to generate the incoming waves to evaluate the motion responses. The procedure can replace a decade of simulations in regular wave with one single run to obtain a complete curve of linear motion response, considerably reducing computation time. A correction procedure is employed to adjust the wave generation signal based on the wave spectrum and achieves fairly better results in the wave tank. Three ship models with five wave conditions are introduced to validate the method. The computations in this paper are completed by using the solver naoe-FOAM-SJTU, a solver developed for ship and ocean engineering based on the open source code OpenFOAM. The computational motion responses by the irregular wave procedure are compared with the results by regular wave, experiments and strip theory. Transfer functions by irregular wave closely agree with the data obtained in the regular waves, showing negligible difference. The comparison between computational results and experiments also show good agreements. The results better predicted by CFD method than strip theories indicate that this method can compensate for the inaccuracy of the strip theories. The results confirm that the irregular wave procedure is a promising method for the accurate prediction of motion responses with less accuracy loss and higher efficiency compared with the regular wave procedure.     

内河航道中船行波在岸坡爬高的数值模拟

该文基于RANS方程、RNG k-ε湍流模型建立数值波浪水池,用VOF法追踪自由面的位置,并模拟了内河航道中船行波的生成、传播、爬高和岸壁反射过程,且与典型断面航道中船行波在岸坡最大爬高和回落的现场测量值进行了比较,验证了数值模型的有效性。通过对航道中船行波进行数值模拟,获得了船行波的波形及其在岸坡上爬高与回落的最大值。分析了船舶吃水、航速和航道岸坡倾角对特征波高以及最大爬高与回落的影响。最后建立了计算船行波特征波高、爬高和回落的经验公式。     

Sea level variability in East China Sea and its response to ENSO

Sea level variability in the East China Sea (ECS) was examined based primarily on the analysis of TOPEX/Poseidon altimetry data and tide gauge data as well as numerical simulation with the Princeton ocean model (POM). It is concluded that the inter-annual sea level variation in the ECS is negatively correlated with the ENSO index, and that the impact is more apparent in the southern area than in the northern area. Both data analysis and numerical model results also show that the sea level was lower during the typical El Nio period of 1997 to 1998. El Nio also causes the decrease of the annual sea level variation range in the ECS. This phenomenon is especially evident in the southern ECS. The impacts of wind stress and ocean circulation on the sea level variation in the ECS are also discussed in this paper. It is found that the wind stress most strongly affecting the sea level was in the directions of 70o and 20o south of east, respectively, over the northern and southern areas of the ECS. The northwest wind is particularly strong when El Nio occurs, and sea water is transported southeastward, which lowers the sea level in the southern ECS. The sea level variation in the southern ECS is also significantly affected by the strengthening of the Kuroshio. During the strengthening period of the Kuroshio, the sea level in the ECS usually drops, while the sea level rises when the Kuroshio weakens.     

Process control of the sand wave migration in Beibu Gulf of the South China Sea

Based on the environment characteristics of the Beibu Gulf of South China Sea, a quasi-three-dimensional physical model is built.By coupling the bottom boundary layer with the two-dimensional tidal current field near the seabed surface, the quasi-three-dimensional hydrodynamic numerical simulation is carried out.The sand wave migration process is dealt with by coupling the hydrodynamic model with the sediment transport model.The computational results are shown to be in good agreement with the observed data,...     

Evaluation of numerical wave model for typhoon wave simulation in South China Sea

The simulating waves nearshore (SWAN) model has typically been designed for wave simulations in near-shore regions. In this study, the model's applicability to the simulation of typhoon waves in the South China Sea (SCS) was evaluated. A blended wind field, consisting of an interior domain based on Fujita's model and an exterior domain based on Takahashi's model, was used as the driving wind field. The waves driven by Typhoon Kai-tak over the SCS that occurred in 2012 were selected for the numerical simulation research. Sensitivity analyses of time step, grid resolution, and angle resolution were performed in order to obtain optimal model settings. Through sensitivity analyses, it can be found that the time step has a large influence on the results, while grid resolution and angle resolution have a little effect on the results.     

“奋威”轮沉船海域水动力条件数学模型研究

通过建立波浪潮流数学模型,对"奋威"轮沉船坐浅期间海域水动力条件进行模拟计算。结果表明:(1)沉船仅对局部海域的流态有影响,总体影响不大,沉船附近涨落急时流速为1 m/s左右;(2)沉船坐浅期间,沉船附近最大波高可以达到2.63 m左右,大风情况下的巨浪可能对沉船的稳定性造成影响。模拟结果为沉船沉降计算提供水动力条件。     

基于拉格朗日粒子追踪的渤海冬季与夏季环流及影响因素

基于三维非结构有限体积海洋模式(FVCOM)对渤海环流进行了数值模拟研究.数值模拟中采用三角形网格,以更好地拟合渤海复杂的岸线边界.潮位、潮流、温盐模拟结果验证良好.通过对粒子的拉格朗日追踪研究了渤海冬季与夏季环流及潮、风、海气热交换和人海径流对渤海环流的影响.研究表明:粒子输移存在明显的三维结构;与渤海中部及海峡附近...