远区台风“三巴”对长江口波浪动力场的作用机制

针对远区台风对河口波浪动力场的影响问题,利用第三代波浪模式SWAN计算了远区台风"三巴"期间长江口波浪动力场分布,分析了陆架至河口区的波浪能量耗散和波致泥沙侵蚀的时空分布,发现波浪由外海向近岸传播过程中,波-波相互作用导致能量由高频向低频转换,周期和波长逐渐增大,近底层轨道流速增大,能量密度增高;阐明白帽破碎是维持深水区波浪能量平衡和限制波高成长的主要机制,底摩擦耗能和水深诱导的破碎耗能是长江口横沙东滩和崇明东滩邻近海域波高衰减的主要原因;提出波浪产生的底部切应力与相对水深有关,当波浪传播到浅水区时,波长和周期越大,波浪切应力越大。研究揭示了与河口相距数百公里的远区台风能够对长江口波浪动力场产生明显影响,河口水下三角洲前缘是最容易受到波浪侵蚀的区域,研究成果弥补了目前关于陆架远区台风对河口波浪动力场影响研究的不足,对深化认识远区台风对长江口动力环境、地貌演变、航运安全和滩涂保护等有重要科学意义。     

Vertical variations of wave-induced radiation stress tensor

INTRODUcrIONThe concept of radiation stress was deve1oPed by tonguet--Higgins and Stewart (1964 ),who intreduced the definition of radiation stress as the excess mornentum due to the presence ofwaves, on the basis of time-averaged laws of Newtonian fluid mechanics and the assmption ofa unifOrm velocity distribution over depth. Subequently, the theory has been applied success-fully in the investigation of phenomena such as wave set-up and set--down (Bowen et al.,l968), longshore currents …     

An Experi mental Study on Wave-Induced Dynamic Stresses in Seabed

1 .IntroductionEvery year ,Taiwanis subjectedtotwo or three typhoonintrusions in average which always causedisasters . Most of the disasters which occur around the coastal zone are due to seabed instability andcoastal structure destruction caused bytyphoo…     

Mechanism of sea ice formation based on comprehensive observation data in Liaodong Bay,China

Sea ice disaster is one of the principal natural hazards that affect some coastal areas of China,and the formation of ice cover in a wave field has important characteristics.However,analysis of the mechanism in which waves affect the thermodynamic process of sea ice is lacking,and the influence of waves is not taken into consideration in numerical models of sea ice,largely because of a lack of simultaneous observations of waves and sea ice.Using observational data of the sea ice cycle in the coastal waters of Liaodong Bay(China),we analyzed the characteristics of hydrology,meteorology,and sea ice thickness during the formation of sea ice,and explored the changes in the interrelationships among heat fluxes,waves,and sea ice under actual sea conditions.The results could provide a decision-making support as a reference to the establishment and improvement of China's early waming system to sea ice disasters,and the protection of ice drilling operations and production platform safety.     

2D Wave setup behind submerged breakwaters

In addition to reducing the incoming wave energy, submerged breakwaters also cause a setup of the sea level in the protected area, which is relevant to the whole shadow zone circulation, including alongshore currents and seaward flows through the gaps. This study examines such a leading hydraulic parameter under the simplified hypothesis of 2D motion and presents a prediction model that has been validated by a wide ensemble of experimental data. Starting from an approach originally proposed by Dalrymple and Dean [(1971). Piling-up behind low and submerged permeable breakwaters. Discussion note on Diskin et al. (1970). Journal of Waterways and Harbors Division WW2, 423–427], the model splits the rise of the mean water level into two contributions: one is due to the momentum flux release forced by wave breaking on the structure, and the other is associated with the mass transport process. For the first time, the case of random wave trains has been explicitly considered.     

具有不同到达率的带有启动时间及不耐烦策略的多级适应性休假M^X/G/1排队

研究了具有不同到达率的带有启动时间及不耐烦策略的多级适应性休假M^X/G/1排队模型,通过嵌入马尔可夫链方法推导出稳态队长的母函数、等待时间的LST（先到先服务规则）,并验证了稳态队长和稳态等待时间具有随机分解性,而且给出了忙期、全忙期及在线期均值。     

波致应力的近似求解及其太平洋特征分析

基于波致应力计算中对海浪谱和波浪增长率公式的敏感性分析,选择适当的波致应力近似求解方法,计算和探讨了太平洋波致应力的时空分布特征。敏感性分析中,选择了4种常用的波浪增长率公式和3种经验解析海浪谱。推导了计算波致应力的单波公式,并将其与JONSWAP谱积分公式和Elfouhaily谱积分公式进行比较,同时使用了由风速和有效波高资料构造的Elfouhaily谱积分公式计算太平洋波致应力。结果表明:Belcher等(1993)的波浪增长率计算公式估算的波致应力与实验数据吻合度较好,同时适用ERA-interim数据;当波龄小于1.2时运用Elfouhaily谱积分公式更合适,当波龄大于1.2时运用单波公式更快速有效;太平洋的波致应力分布与风场之间存在明显的相关性;2009年1月、4月、7月和10月太平洋波致应力的季节性特征分析表明四个季节的西风带波致应力较其他地区都更强盛,而在时间变化上1月和10月为波致应力整体较为强盛的时期。     

基于可靠性的海洋立管疲劳安全系数研究

综合考虑了立管疲劳安全系数取值的相关因素——立管的安全等级、设计寿命、检验周期、载荷和损伤计算方法等的不确定性,提出了基于可靠度的疲劳安全系数确定方法,筛选了用于计算波致疲劳和VIV(涡激振动)疲劳的随机变量,给出了立管波致疲劳与VIV疲劳安全系数的计算流程,并以某SCR(钢悬链线立管)为例进行了安全系数计算。结果表明,该方法的计算结果优于传统的安全系数确定方法,尤其适合于特殊工程方案或新颖设计的立管疲劳校核。     

非结构化网格下近岸波生流数值模拟

波浪破碎产生的近岸流是近岸海域关键的水动力因素之一。基于近岸波浪的椭圆型缓坡方程和二维近岸波生流方程,建立了非结构化网格下近岸波浪破碎形成的近岸流数值模型。数值模型中,在空间上采用有限体积法进行数值离散,在时间上采用欧拉向前格式数值离散。数值计算结果表明,该数值模型可以有效地模拟近岸波浪破碎产生的近岸流。     

The improvement of the one-dimensional Mellor-Yamada and K-profile parameterization turbulence schemes with the non-breaking surface wave-induced verticalmixing

Both the level 2.5 Mellor-Yamada turbulence closure scheme(MY) and K-profile parameterization(KPP) are popularly used by the ocean modeling community.The MY and the KPP are improved through including the non-breaking surface wave-induced vertical mixing(Bv),and the improved schemes were tested by using continuous data at the Papa ocean weather station(OWS) during 1961–1965.The numerical results showed that the Bv can make the temperature simulations fit much better with the continuous data from Papa Station.The two improved schemes overcame the shortcomings of predicting too shallow upper mixed layer depth and consequently overheated sea surface temperature during summertime,which are in fact common problems for all turbulence closure models.Statistical analysis showed that the Bv effectively reduced the mean absolute error and root mean square error of the upper layer temperature and increased the correlation coefficient between simulation and the observation.Furthermore,the performance of vertical mixing induced by shear instability and the Bv is also compared.Both the temperature structure and its seasonal cycle significantly improved by including the Bv,regardless of whether shear instability was included or not,especially for the KPP mixing scheme,which suggested that Bv played a dominant role in the upper ocean where the mean current was relatively weak,such as at Papa Station.These results may provide a clue to improve ocean circulation models.