A hybrid model for numerical wave forecasting and its implementation-Ⅰ.The wind wave model

The authors make an endeavor to explain why a new hybrid wave model is here proposed when several such models have already been in operation and the so- called third generation wave modej is proving attractive. This part of the paper is devoted to the wind wave model. Both deep and shallow water models have been developed, the former being actually a special case of the latter when water depth is great. The deep water model is exceptionally simple in form. Significant wave height is the only prognostic variable. In comparison with the usual methods to compute the energy input and dissipations empirically or by 'tuning', the proposed model has the merit that the effects of all source terms are combined into one term which is computed through empirical growth relations for significant waves, these relations being, relatively speaking, easier and more reliable to obtain than those for the source terms in the spectral energy balance equation. The discrete part of the model and the implementation of the model as a whole will be discussed in the second part of the present paper.

Mechanistic Drifting Forecast Model for A Small Semi-Submersible Drifter Under Tide–Wind–Wave Conditions

Understanding the drifting motion of a small semi-submersible drifter is of vital importance regarding monitoring surface currents and the floating pollutants in coastal regions. This work addresses this issue by establishing a mechanistic drifting forecast model based on kinetic analysis. Taking tide–wind–wave into consideration, the forecast model is validated against in situ drifting experiment in the Radial Sand Ridges. Model results show good performance with respect to the measured drifting features, characterized by migrating back and forth twice a day with daily downwind displacements. Trajectory models are used to evaluate the influence of the individual hydrodynamic forcing. The tidal current is the fundamental dynamic condition in the Radial Sand Ridges and has the greatest impact on the drifting distance. However, it loses its leading position in the field of the daily displacement of the used drifter. The simulations reveal that different hydrodynamic forces dominate the daily displacement of the used drifter at different wind scales. The wave-induced mass transport has the greatest influence on the daily displacement at Beaufort wind scale 5–6; while wind drag contributes mostly at wind scale 2–4.

DYNAMIC MODEL FOR OIL SLICK DISPERSION INTO A WATER COLUMN- A WINDDRIVEN WAVETANK EXPERIMENT

A dynamic experiment for oil dispersion into a water column was performed with a 21 m long, 0.5 m wide, and 1 m high wind-driven wave tank. At wind velocity between 6-12 m/s and with the oil slide kept constant (about 1 um), the rate of the oil content increase in the water column could be approximated from the difference between the dispersion rate (R) of the oil slick and the coagulation rate (R’) of the dispersed oil slick. Assuming the coagulation rate is directly proportional to the concentration of the water dispersed oil slick (i. e. R’ =KC),, the integral form of the dynamic model can be expressed as C=R*[1-exp(-K*t)]/K and parameters R and K can be regressed with a computer. The relative deviation of model results from the experimental data was mainly less than 10%. The oil slick dispersion rate (R) had exponential relationship with the wind velocity (V), and can be fitted with a formula R=A*(U+1)B.The fitted constant of the coagulation rate, K(0.8-3.0* 10-3 min-1) did not have significant

WIND WAVES SIMULATION IN THE NORTH AREA OF THE SOUTH CHINA SEA

A third generation wave model was developed to simulate wind waves in the South China Sea near Hong Kong. The model solves the energy conservation equation of the two dimensional wave spectrum by directly computing the nonlinear energy interaction among waves of different frequencies, thus avoiding the imposition of restrictions on the shape of the predicted spectra. The use of an upwind difference scheme in the advective terms produces an artificial diffusion which partly compensates the dispersive effect due to the phase velocity differences among various wave components. The use of a semi-implicit scheme for the source terms together with a special treatment of the high frequency tail of the spectrum allows a large time integration step. Verification of the model was done for wave hindcasting studies under conditions of two typhoons and two cold fronts in the north part of the South China Sea near Hong Kong . The model results agree well with the field measurements except that the presence of a

Simulation of Typhoon-Driven Waves in the Yangtze Estuary with Multiple-Nested Wave Models

Typhoon-generated waves are simulated with two numerical wave models, the SWAN model for the coastal and Yangtze Estuary domain, nested within the WAVEWATCHIII （WW3） for the basin-scale East China Sea domain. Typhoon No. 8114 is chosen because it was very strong, and generated high waves in the Estuary. WW3 was implemented for the East China Sea coarse-resolution computational domain, to simulate the waves over a large spatial scale and provide boundary conditions for SWAN model simulations, implemented on a fine-resolution nested domain for the Yangtze Estuary area. The Takahashi wind model is applied to the simulation of the East China Sea scale （3-hourly） and Yangtze Estuary scale （1-hourly） winds. Simulations of significant wave heights in the East China Sea show that the highest waves are on the right side of the storm track, and maxima tend to occur at the eastern deep-water open boundary of the Yangtze Estuary. In the Yangtze Estuary, incoming swell is dominant over locally generated waves before the typhoon approaches the Estuary. As the typhoon approaches the Estuary, wind waves and swell coexist, and the wave direction is mainly influenced by the swell direction and the complex topography.

风浪流耦合作用下锚泊式海上试验平台的水动力特性试验

为了研究国家海洋试验场的“国海试1”平台与锚泊优化方案是否满足设计要求,采用物理模型试验方法,制作1∶30试验平台模型,在国家海洋技术中心海洋动力环境实验室开展百余组不同波高、波周期、波向的不规则波、定常风和等效均匀流联合作用下,两点式躺地链系泊状态下的模型运动响应研究。对比分析试验结果与对应试验平台的设计指标,结果表明:同样海况下,风浪与潮流同向时,试验平台的运动响应更剧烈;流速1.14 m/s、4级海况时,试验平台最大横摇角为10.41°,“国海试1”平台无法开展正常的吊装工作;流速1.14m/s、6级海况时,试验平台最大横摇角为15.07°,“国海试1”平台搭载的试验测试设备无法正常工作;流速1.14 m/s、8级海况时,试验平台最大横摇角为20.21°,平台存在安全隐患,应采取避险措施;“国海试1”满足抗7级风浪的设计要求。该研究成果验证了改进后的国家海洋综合试验场“国海试1”平台满足抗7级海况的设计要求。因此,建议“国海试1”平台在6级海况下应停止试验作业,8级海况下应采取必要的避险措施。该研究为同类新型海洋平台水动力研究提供了参考。

基于WAVEWATCH-Ⅲ模式的一次冷空气过程海浪场模拟研究

以具有高精度和较高分辨率的CCMP(Cross-Calibrated,Multi-Platform)风场驱动第三代海浪模式WW3(WAVEWATCH-III),对2009年1月12日前后的一次冷空气所致的中国海海浪场进行数值模拟,并在国内首次利用来自朝鲜半岛的观测资料对模拟数据的有效性进行检验。研究发现:(1)以CCMP风场驱动WW3海浪模式,可以整体上较好的刻画出此次中国海范围由冷空气造成的海浪场,模拟的有效波高(SWH——Significant Wave Height)精度接近高度计的观测精度,系统上稍大于高度计反演的SWH,模拟的SWH和观测值相比略有滞后的现象,观测数据跳跃较为明显,而模拟数据的走势则更为平缓;(2)此次冷空气过程中,第一岛链以内的海域的海浪场与风场具有较好的一致性,第一岛链以外的大洋中,海浪场与海表风场的对应关系明显不如第一岛链以内,以菲律宾以东的洋面最为显著的。

风力发电机叶片面内振动抑制的主动控制

为解决风力发电系统中叶片振动问题,提出一种用于抑制叶片面内振动的主动控制方法。首先将叶片等效成均匀截面悬臂梁,根据材料力学相关理论求解其挠度表达式,包括自由振动和强迫振动,再根据挠度表达式计算旋转平面内的振动力矩,并建立叶片端到电机端的力矩传导模型,最后在电机端调制出用于消振的力矩。仿真结果证实所提出方法能够有效减小叶尖处位移,抑振率可达70%以上,实验结果表明,电机转矩的波动幅度明显降低,该方法可以大大减少因叶片振动引起的风力发电系统故障。

舰船环境适应性设计方法探索与实践

探索舰船环境适应性的设计方法,以提高舰船在各种复杂环境下的适应能力。分析了舰船环境适应性设计中面临的若干问题和改进提高方向,参考借鉴国内外航空航天、电子等行业成功经验,提出了指导舰船环境适应性设计的主要设计原则和工作内容。围绕改善环境条件、加强耐环境能力设计这2个方面,提出了3种环境适应性设计方法,包括基于规范的设计方法、基于环境仿真的设计方法、基于预使用验证的设计方法。根据舰船风浪环境适应性设计的特点和要求,选择采用环境仿真和模型试验技术开展了应用研究。基于分析结果,提出了增加水线面系数、调整浮心、优化线型等多项改进措施建议。采用环境仿真和模型试验相结合的方式,可有效支撑舰船风浪环境适应性设计和评估,这一方法具有较高的工程推广应用价值。另外,未来应加大环境仿真技术的研究和应用力度,尝试开展多因素综合环境仿真,以进一步提高舰船的环境适应性。

考虑时间相关性的风速和波浪高度短期预测

风与波浪高度是海洋工程设计的重要参数之一,其准确预测具有重要的工程意义。针对波浪高度复杂多变、难以预测的挑战,本文考虑时间相关性,利用长短时记忆(Long-Short-Term Memory,LSTM)神经网络方法建立风和波浪高度的短期预测模型。首先,对波浪高度和风速等海洋环境原始时间序列进行分析,并选取不同时间间隔对浪高和风速极值进行取值;其次,对风速与波浪高度开展相关性分析,并基于LSTM方法,构建风和波浪高度单步预测模型。在时间间隔为0.5 h时,波浪的预测误差为0.12 m;进而构建风和波浪联合预测模型,预测风速下的波高预测误差仅为0.12m,与实测风速下的波浪预测误差基本一致。

Wave-CISK、蒸发-风反馈和低频振荡

本文利用一个包含有Wave-CISK和蒸发-风反馈机制的斜压半地转模式来讨论低纬大气运动,其中引入了反映CISK机制的无量纲对流凝结加热参数η和反映蒸发-风反馈机制的无量纲参数α_0,求得了η=0情况下的解析解及η≠0情况下的一级近似解,对η≠0情况下向东传播的类似于低频振荡的波动进行了讨论,从理论上指出了蒸发及非均匀加热对低频振荡的维持所起的重要作用.

风浪作用下海上风电结构动力响应数值仿真

为了能够更好利用海洋资源,提高发电效率,提出了风浪作用下海上风电结构动力响应数值仿真方法。建立波动力平衡方程获取海波谱,计算出风场平均波高与周期。利用离散频谱逼近目标随机过程,用互功率频谱密度矩阵求拟脉动风场的风速时程曲线,将平均风速和谐波叠加风速相加,得到单位高度风荷载。按照拟层流风波产生机理,构建波浪谱模型,采用莫里森公式计算结构波浪荷载,考虑风浪间的相关性,将波浪参数代入风浪谱,得到风电结构响应数值。通过仿真得出在不考虑波面高度变动的情况下,波面力在波峰处被低估,在波谷处被高估,波面高度的变化会对风电结构动态响应产生一定影响,得出结果可以为保障电能效益提供参考。

波浪荷载对海上风电筒型基础结构振动响应的影响

以混凝土弧线段为过渡段的宽浅式筒型基础所受的波浪荷载较大,易对整个海上风电结构体系的振动响应产生影响。针对某海上风电筒型基础结构,文章基于现场实测数据构建了整机有限元模型,通过数值模拟方法分析波浪荷载对海上风电筒型基础结构塔筒顶部振动响应的影响。结果表明:在风机运行过程中,由风荷载所引起的塔筒顶部的振动响应较波浪荷载所引起的响应要大;在浪高较小工况下,相较风荷载,波浪荷载的影响可以忽略;波浪荷载对风机塔筒顶部振动响应的影响随着外界风速及浪高的增大而增大,其对塔筒顶部振动位移响应的影响比振动加速度大。

基于SWAN模型下的马拉博油罐区深水波浪条件分析

在深水波浪条件下,油罐区的稳定性和安全性都面临着极大的挑战,对所在海域的风与波浪耦合作用的波浪分析变得至关重要。本文基于第三代海浪数值模型SWAN,依据CCMP和CFSR数值风场资料,建立南大西洋海浪后报数据集。通过与尼日利亚拉格斯外海Bonga站和纳米比亚卡拉斯外海Kudu站的实测数据资料进行对比,验证了数据集的合理性。并对赤道几内亚马拉博外海深水波浪条件进行分析,为后续油罐区项目建设提供数据参考。

A Study on the Spectral Form of Nearshore Water Waves

The spectral form of wind waves is investigated based on the ocean wave data observed at three nearshore stations of Taiwan. In this study, the generalized forms of Pierson-Moskowitz spectrum and JONSWAP spectrum are used to describe the local wave spectrum by selecting suitable spectral form parameters. It is shown that, at a specific site, the similarity of wave spectral form exists. Thus it is possible to use a representative spectral form for a given nearshore region to describe the wave spectrum at this nearshore. On the other hand, the effects of relative water depth on spectral form are examined. The feasibility of two spectral models in finite water depth is evaluated by using the same field wave data.

A method to predict typhoon waves

The presented method for numerical typhoon wave prediction is composed of a scheme for real time pressure forecasts, a marine wind numerical model and a typhoon wave numerical model. In the Northwest Pacific Ocean and China seas where water depth is over 20 m, a hybrid wave model [Wen Shengchang, Zhang Dacuo, Chen Bobal and Guo Peifang. 1989, Acta Oceanologica Sinica, 8 (1), 1～14; Zhang Dacuo, Wu Zengmao,Jiang Decai, Wang Wei, Chen Bobai, Tat Weitao, Wen Shengchang, Xu Qichun and Guo Peifaug. 1992, Acta Oceanologica Sinica, 11 (2), 157～178] is employed with 1°×1°grids, while in the South China Sea and East China Sea where typhoon frequently appears, the WAM model (WAMDI Group. 1988, Journal of Physical Oceanography, 18, 1755～1810) of shallow water version is embedded with (1 /4 )°×(1 /4)°grids. The boundary condition at the open boundary of the WAM model is provided by the hybrid model. After 3 a of testing forecasts(Yang Chuncheng, Dai Mingrui and Zhang Dacuo. 1992, International Symposium on Tropical Cyclone Disasters, October 12～16, Beijing, 404～409 ) and improvement, this system was put into operational use on the forecasting computer network of National Marine Environment Forecast Center of China in June, 1993. The wave predictions of 22 typhoon events show that the system is stable and prompt, and the forecast results are satisfactory. This system provides reliable numerical products for the disaster-prevention forecasts. The product is broadcasted in CCTV News at every noon.

Simulation of wind-induced near-inertial oscillations in a mixed layer near the east coast of Korea in the East/Japan Sea

Using a simple damped slab model, it was possible to show that a local wind induced 88% （15 of 17） of the near-inertial oscillations （NIO） observed in the mixed layer near the east coast of Korea from 1999 to 2004. The model, however, overestimated the energy level in about two-thirds of the simulated cases, because the slab model was forced with winds whose characteristic period was shorter than the damping time scale of the model at 1.5 d. At the observation site, due to typhoons and orographic effects, high-frequency wind forcing is quite common, as is the overestimation of the energy level in the slab model results. In short, a simple slab model with a damping time-scale of about 1.5 d would be enough to show that the local wind was the main energy source of the near-inertial energy in this area, but the model could not be used to accurately estimate the amount of the work done by the wind to the mixed layer.

风浪流耦合作用下小型LNG船舶运动响应试验研究

小型LNG船尤其是小型多功能LNG加注船迎来了新的发展空间,在风浪流作用下其运动响应还需要深入研究。以曹妃甸港某LNG码头为例,采取物理模型试验,模拟了风、浪、流共同作用下4万m 3LNG船舶与1.2万m 3LNG加注船的运动响应过程,测量了系缆张力及护舷撞击力。同时针对4万m 3LNG船舶,开展系缆方式优化研究,提供2 a一遇波浪条件下满足规范要求的系泊方案,为工程设计提供依据。

极端波浪条件下深水导管架基础结构波浪总力试验研究

波浪力对海上风电深水导管架基础结构的稳定性和安全性至关重要。通过波浪物理模型试验对极端波浪条件下深水导管架基础结构的波浪总力进行了试验研究,试验水深包括50m和70m两种,在1000a一遇波浪条件下,分别分析了深水导管架结构所受的波浪总水平力和垂直力。研究结果表明:相同重现期极端波浪作用下,70m水深情况下的导管架结构波浪总水平力小于50m水深的结果,但是70m水深的导管架结构波浪总水平力弯矩大于50m水深的结果;相同水深、水位和波浪条件下,导管架结构受到的波浪总垂直力明显小于波浪总水平力;在相同重现期极端波浪作用下,低水位情况时70m水深的导管架结构波浪总垂直力与50m水深的结果差别不大,但是在高水位时,由于在70m水深的极端波浪条件下波峰可冲击作用到上部平台底面,70m水深的导管架结构波浪总垂直力明显大于50m水深的结果。

基于FHDI-GNWM的某海域波浪时空分布特性分析

采用2015—2019年的FHDI-GNWM后报波浪资料,并结合波浪数学模型,对某海域的波浪分布特征进行了初步统计分析,得到如下结论:1)海区波向与风向基本一致,冬季主浪向为E向;夏季主浪向为SSW向;2)海区波浪以风浪为主,且表现出明显的季风特征,夏季波高较小,平均波高介于0.4~0.7 m;冬季波高较大,平均波高介于0.85~1.1 m。此外,基于某集装箱码头项目,结合船舶系泊试验,分析了波浪引起船舶装卸不可作业时间。文章成果对认识某近岸海域的风、浪特征以及对相关码头设计具有一定参考价值。