Wave run-up and overtopping on smooth and rough slopes of coastal structures

A series of hydraulic model tests has been carried out in a glass wave flume to investigate the influences of wave height, wave period, wave steepness, surf similarity parameter, roughness, layer thickness and porosity on wave run-up and overtopping of 1:2 sloped impermeable and permeable breakwaters fronted by a 1:10 gentle, smooth beach slope. The analysis of results involves the correlation between the overtopping energy transfer with the relative wall height and the relationship between wave run-up and overtopping rate. Further, measured wave run-up and overtopping rates are compared with the results given in the Shore Protection Manual (1984), Automated Coastal Engineering System (1992)and results of other investigators.     

A note on estimation of the Jacobian elliptic parameter in cnoidal wave theory

A new and simple calculating technique for the Jacobian elliptic parameter is presented in this study. The technique is very useful in generating a train of cnoidal waves in both laboratory and numerical wave tanks. Upon specification of water depth, the wave height and either the wave period or the wavelength, the proposed technique uses the Newton–Raphson method to estimate the Jacobian elliptic parameter directly, without trial and error procedures or look-up in tables. It is shown that the technique provides equally accurate results as the ad hoc methods previously used.     

机载雷达高度计对海况及海面风速的测量研究

运用我国自行研制的ＺＨＧ－１型Ｘ波段机载雷达高度计于１９９５年４月１３日－４月１８日在青岛附近海域进行的海上飞行实验数据，及导出的均方根波高、有效波高、均方根波陡算法模型，得到了上述海况参数值。     

JONSWAP谱和N谱的几个对应特征量间的关系

研究了风浪频谱ＪＯＮＳＷＡＰ谱的峰度因子γ、尖度因子Ｐｊ和Ｎ谱尖度因子ＰＮ，参变量ｐ，ｑ间的关系；并在此关系上给出了由这两种谱计算的几个对应参量间的关系，在使用不同的谱形进行特征量的计算时，应注意不同频谱间的成长因子致性，以免引起计算结果的错误。     

确定连续系统参数的时域方法

提出一种确定连续系统参数的时域方法。该方法利用方波输入和系统稳定性，离析出输出采样信号与结构参数的内在联系，推导出确定连续系统结构参数的算法．指出该算法与辨识方法相结合，可实现对含随机干扰的连续系统结构参数的估计．     

季节内SST和混合层深度变化的模式研究

用Niiler—Kraus类型的混合层积分模式,对TOGA—COARE强化观测期间由《实验3号》科学考察船观测资料得到的混合层深度和SST在季节内时间尺度的变化进行了模式研究。指出:1.混合层耗散参数与较长时间尺度过程风应力的变化存在着比较好的对应关系;2.模式可以较好的对风场和热通量场在季节内时间尺度的变化作出响应,模拟出季节内时间尺度SST的变化;3.Niiler,-Kraus模式在考虑耗散作用后,可用于海洋季节内时间尺度变化的模式研究。     

On the recovery of surface wave by pressure transfer function

Except the commonly selected pressure transfer function derived from the linear wave theory, a previous study on the pressure transfer function for recovering surface wave from underwater pressure transducer suggested that the pressure transfer function is a function of frequency parameter only. With careful analysis, this study showed that the pressure transfer function should include a transducer submergence parameter as that given by the linear theory. It was found that the previously suggested empirical formula should be restricted to measurements with the pressure transducer close to the surface; otherwise overestimation of wave height would result. Field measurements were carried out with an acoustic wave gauge and a synchronized pressure transducer located at various depths with submergence parameter close to 1 (near the sea floor). It was shown that the previous one-parameter empirical formula might overestimate the significant wave height by more than 30%. This study found that with deep-water wave bursts excluded, the transfer function based on the linear wave theory provided a fairly good estimation on the significant wave heights, with an average deviation of 3.6%.     

Degradation in Cemented Marine Clay Subjected to Cyclic Compressive Loading

The influence of cyclic loading on the strength and deformation behavior of cemented marine clay has been studied. This marine clay is of recent Pleistocene origin and deposited in a shallow water marine environment. Open pits were dug in sheeted enclosures and from these pits, undisturbed samples were taken for strength testing. A series of standard triaxial shear tests and stress controlled one-way cyclic load tests were conducted at consolidation stress ranges below and above the preconsolidation pressure. For the stress levels below the preconsolidation pressure, the cyclic loading has brought about the collapse of the cementation bond through an increase in strains, and at higher pressure ranges, the soil behaves like typical soft clay. This experiment studied the rate of development of strain and pore water pressure and shows that rate is a function of number of cycles, applied stress, and stress history. In addition, soil degradation during cyclic loading is studied in terms of Degradation Index. Attempt has been made to predict stain, pore water pressure, and degradation index through an empirical model.     

Semi-Probabilistic Evaluation of System Redundancy for Existing Offshore Structures

In this paper, a new definition of structure system redundancy is proposed in view of the various measures for structure redundancy. By introducing the terms of structure system failure at the mechanism level and equivalent reliability index, the safety for existing offshore platforms can be evaluated by the semi-probabilistic method presented in this paper. Some numerical examples are given and satisfactory results have been obtained.