Statistics of nonlinear wave crests and groups   总被引：1，自引：0，他引：1  

M. Aziz Tayfun   《Ocean Engineering》2006,33(11-12):1589-1622

Groups of large nonlinear waves with sharper higher crests can pose hazards to ships, induce harbor resonance and cause wave-overtopping of fixed and floating structures. Past interest in wave groups has mostly been focused on the statistics and modeling of linear wave groups. Studies on nonlinear wave groups are surprisingly few, and address deep water waves only. Here, statistics of nonlinear wave crests and wave-crest groups in deep and transitional water depths are considered, using an appropriate second-order representation for crest heights and the continuous wave-envelope approach. In particular, theoretical expressions describing the statistics of nonlinear wave crests and their groups are posed in the form of a simple second-order transformation of well-known results on linear waves. Predictions from the transformation so posed compare well with nonlinear wave data gathered in the North Sea, and demonstrate that nonlinearities do affect the statistics of large wave crests and their groups significantly.  相似文献   

Three-dimensional numerical simulation of obfique wave action on vertical walls     

LI Benxia YU Xiping YU Yuxiu 《海洋学报(英文版)》2006,25(1):147-153

A three-dimensional numerical model based on the potential theory was developed to study the oblique wave action on vertical walls. A source term inside the domain was used to generate incident waves and outgoing waves were dissipated by sponge layers and transmitted by radiation boundaries. The finite difference method was used to solve the governing equations and boundary conditions in the regular transformed domain in σ-coordinate. Satisfactory agreements between the numerical predictions and experimental results of wave force were obtained. It is concluded that the maximum wave force acting on the vertical walls is induced by the obliquely incident waves rather than the normally incident waves.  相似文献   

双层局部开孔板沉箱对波浪反射的理论研究   总被引：1，自引：0，他引：1  

李玉成  刘洪杰滕斌 《海洋工程》2005,23(1):18-27,32

提出了一种用于研究由双层开孔板和一个不透水后板的开孔结构对斜向波反射率的理论分析方法。整个流域被分成三个子域，在每个子域内应用特征函数展开法以得到该域内包含未知展开系数的势函数的表达式，在速度势的展开中，考虑了非传播模态波浪的影响。通过匹配开孔板处的边界条件可以求解待定的展开系数，继而求解双层开孔板防波堤结构对斜向波的反射率。数值计算结果与试验结果进行了比较，符合较好。并进一步讨论了几个重要因素对反射系数的影响。  相似文献   

Analytic Solution of Interaction Between Surface Waves and Floating Elastic Plates with Elastic End-Restraints     

赵存宝张嘉钟  邢海燕黄文虎 《中国海洋工程》2007,21(1):23-38

Based on the dynamic theories of water waves and Mindlin plates,the analytic solution of interaction between surface waves and two-dimensional floating elastic plates with edge-restraint is constructed by use of the Wiener-Hopf technique.Firstly,without regard for elastic edge restraint,the wave-induced responses of elastic floating plate analyzed by the present method are in good agreement with the results from literature and experimental results.Therefore,it can be shown that the present method is valid.Secondly,three end-restraint cases(i.e.,the left-end elastic restraints,the both-end elastic restraints,and the right-end elastic restraints)are proposed to reduce the vibration of floating plates,in which the spring is used to connect the sea bottom and the floating plate's left(or right)edge.The relations between the spring stiffness and the parameters of wave-induced responses of floating plates are discussed.Moreover,the effective method to reduce the vibration of floating elastic plates can be obtained through comparison.  相似文献   

Numerical Investigation on the Generation and Propagation of Irregular Waves in A Two-Dimensional Wave Tank     

Ruey-syanSHIH Chung-renCHOU JohnZ.YIM 《中国海洋工程》2004,18(4):551-566

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Metridia pacifica in Dabob Bay, Washington: The diatom effect and the discrepancy between high abundance and low egg production rates   总被引：1，自引：0，他引：1  

Claudia Halsband-Lenk   《Progress in Oceanography》2005,67(3-4):422

Information on life cycle strategies and reproductive parameters of Metridia pacifica is scarce, despite its importance in the zooplankton of the subarctic Pacific. In many regions it occurs in high abundance, but reproductive rates, when reported, are usually low. This discrepancy was studied in Dabob Bay, Washington, USA, in the context of an investigation of the effect of diatom blooms on the reproductive success of copepod grazers.In situ egg production rates of M. pacifica were measured in spring and mid-summer with standard methods (multi-wells) and a new incubation chamber (spawning towers) that separates the spawning female from its eggs and allows the eggs to develop undisturbed. Many females did not produce eggs, possibly due to a high fraction of immature individuals. Egg production rates were variable, but clutch sizes were higher in spawning towers, and estimates of female egg cannibalism revealed that females consume many eggs shortly after their release. Thus, a separation of females and eggs is mandatory for accurate measurements of M. pacifica egg production rates. The maximum clutch sizes recorded in our study were comparable to measurements for other calanoids. However, unviable eggs were a large fraction of those spawned, independent of incubation method, especially in late winter and early spring. In order to assess whether the diatom effect may be responsible for low viability of embryos and nauplii, we also measured in situ grazing. Adult females were omnivorous, but they ingested some diatoms that rank among the strongest anti-mitotic toxin producers known so far. Although M. pacifica’s vertical migration behavior suggests opportunistic feeding on abundant food during their short stay in the phytoplankton-rich surface, they often ignored the food items that contributed most to microplankton carbon concentrations. Thus, their feeding strategy remains ambiguous. Due to severe reproductive failure early in the season, recruitment was impaired in spring, while the population increased, reaching high abundance in mid-summer when reproductive output was low. While advection and interannual variability in bloom conditions might compensate for the losses described here, the paradox of high Metridia abundance versus low reproductive success still requires further investigation, and methodological constraints need to be ruled out in future studies.  相似文献   

Flow fields in reflected waves at a sloped sea wall     

Gerald Müller   《Ocean Engineering》2007,34(11-12):1786-1789

Wave run-up, and flow visualization experiments were conducted with a 1:2 sloped sea wall model. The visualization experiments gave an overview of flow fields in reflected, non-breaking conditions. Maximum particle velocities were found to be significantly smaller than suggested in the literature. Downrush produced a fast sheet flow, extending down to the toe of the sea wall. This created a ‘reverse’ breaker during the retreat of the initially non-breaking wave, which explains the high-energy dissipation rates for non-breaking waves reported in the literature. Embankments may therefore be exposed to wave impact pressures in areas up to 1.18H₀ below MWL.  相似文献   

Seasonal Variability of Near-Surface Heat Budget of Selected Oceanic Areas in the North Tropical Indian Ocean   总被引：1，自引：0，他引：1  

Chithra Shaji  Satoshi Iizuka  Tomonori Matsuura 《Journal of Oceanography》2003,59(1):87-103

The results obtained from an Ocean General Circulation Model (OGCM), the Modular Ocean Model 2.2, forced with the National Center for Environmental Prediction/National Center for Atmospheric Research reanalysis data, and observational data have been utilized to document the climatological seasonal cycle of the upper ocean response in the Tropical Indian Ocean. We address the various roles played by the net surface heat flux and the local and remote ocean dynamics for the seasonal variation of near-surface heat budget in the Tropical Indian Ocean. The investigation is based in seven selected boxes in the Arabian Sea, Bay of Bengal and the Equatorial Indian Ocean. The changes of basin-wide heat budget of ocean process in the Arabian Sea and the Western Equatorial Indian Ocean show an annual cycle, whereas those in the Bay of Bengal and the Eastern Equatorial Indian Ocean show a semi-annual cycle. The time tendency of heat budget in the Arabian Sea depends on both the net surface heat flux and ocean dynamics while on the other hand, that in the Bay of Bengal depends mainly on the net surface flux. However, it has been found that the changes of heat budget are very different between western and eastern regional sea areas in the Arabian Sea and the Bay of Bengal, respectively. This difference depends on seasonal variations of the different local wind forcing and the different ocean dynamics associated with ocean eddies and Kelvin and Rossby waves in each regional sea areas. We also discuss the comparison and the connection for the seasonal variation of near-surface heat budget among their regional sea areas. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

On the adequacy of second-order models to predict abnormal waves     

P. Petrova  Z. Cherneva  C. Guedes Soares   《Ocean Engineering》2007,34(7):956-961

The paper is intended to extend the investigations about the nature of abnormal waves that have been reported in the work of Guedes Soares et al. (Characteristics of abnormal waves in North Sea states. Applied Ocean Research 25, [337–344]). The same dataset gathered at the oil platform North Alwyn in the North Sea during the November storm in 1997 is used along with the time series from the Draupner platform, in which an abnormal wave occurred. The data are reanalyzed from the viewpoint of the applicability of second-order models to fit large waves. The observed results confirm that the second-order approximation is not adequate to describe highly asymmetric and abnormal waves.  相似文献   

Experimental survey of the hydrodynamic performance of a small spar buoy     

Rgis Capobianco  Vincent Rey  Olivier Le Calv 《Applied Ocean Research》2002,24(6):309-320

The objective in this experimental work is to evaluate the capability of several cylindrical buoys to follow and measure waves. Eleven configurations have been studied, eight among which were furnished with disks of different diameters at the waterline. The experiments took place in the test basin at ISITV. On the one hand, we have obtained a set of transfer coefficients for each frequency and each configuration in regular waves. On the other hand, we have determined the corresponding transfer functions, then we have used the latter to measure irregular waves. The time signals as measured by the buoys with and without corrections have been compared with wave gage measurements and subjected to a wave-by-wave analysis. The results allow the conclusion that the buoy with a medium size disk constitutes the best compromise. In fact, it permits the buoy to follow the free surface while minimizing parasitic motions.  相似文献