Stone mobility and longshore transport at reshaping breakwaters     

Alberto Lamberti  Giuseppe R. Tomasicchio   《Coastal Engineering》1997,29(3-4)

Physical model tests have been performed in two different wave flumes to analyse the threshold of stone movement and quantify the frequency and length of displacements due to head-on wave attacks at a reshaping breakwater. Data on stone movements were obtained from the observation of cumulative displacements at the end of each wave attack and from video records during the attack. Threshold conditions, frequency of movement and displacement length are expressed as function of a suitably modified stability number.A simple model is defined relating longshore transport due to oblique wave attack to stone mobility. The transport model is based on the assumption that movement statistics is affected by obliquity only through the appropriate mobility index and that stones move during up- and down-rush in the direction of incident and reflected waves. Without any calibration, results compare favourably with experimental data available in literature in the range of low mobility conditions where movement statistics was observed. A calibration is provided in order to obtain an accurate transport formula valid in a wide mobility range i.e. for reshaping breakwaters and up to gravel beaches.  相似文献   

一般曲线坐标系下波浪传播的数值模拟   总被引：9，自引：2，他引：9       下载免费PDF全文

张洪生  丁平兴  赵海虹 《海洋学报》2003,25(1):110-119

在曲线坐标系下,建立了缓变水深水域波浪传播的数值模拟模型.模型适宜于复杂变化的边界形状,克服了各种代数坐标变换的局限性.在建立模型时,将原始的椭圆型缓坡方程的近似型式——依赖时间变化的抛物型方程,作为控制方程,既克服了一般抛物近似方法的缺点,又便利了方程的求解;从开边界条件、不同反射特性的固壁边界条件相统一的表达式出发,对边界条件进行处理;用ADI法数值求解控制方程.对模型的验证表明,数值解与物模实验值吻合良好,模型对于具有复杂边界的工程实际有较强的适应性.  相似文献   

淡水入流的生态学意义与其研究现状     

李心铭 《海洋湖沼通报》1996,(4):60-67

由于来自江河的淡水在多数情况下携带大量的营养盐入海，河口海区成为适合于特殊门类的有机物生长的有利海洋环境。与此同时，大量的人类与工业废弃物也随着江河径流入海，从而严重地影响到河口海区的生态环境。鉴于上述原因，淡水入流的生态学 意义现正被广泛地研究。  相似文献   

南海曾母盆地油气地质条件及其分布特征     

刘宝明  金庆焕 《热带海洋学报》1997,(4)

通过分析曾母盆地近几十年来的油气田（井）勘探资料和近年来的地球物理调查成果，在研究区域地质、沉积特征与烃源岩演化关系的基础上，论述了曾母盆地的油气地质条件及其分布特征，并总结其分布规律性。  相似文献   

Interannual fluctuations in recruitment of walleye pollock in the Oyashio region related to environmental changes     

Osamu Shida  Tomonori Hamatsu  Akira Nishimura  Akifumi Suzaki  Jun Yamamoto  Kazushi Miyashita  Yasunori Sakurai 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2822

The Japanese Pacific walleye pollock (Theragra chalcogramma) stock is the largest stock of this species in Japanese waters. It is a key component of the Oyashio ecosystem. In southern Hokkaido waters, these fish spawn mainly during January and February near the mouth of Funka Bay (FB), and most eggs and larvae are transported into FB. During midsummer juvenile pollock migrate along the southern coast of Hokkaido to a nursery ground on the continental shelf off eastern Hokkaido (Doto area). However, some eggs and larvae are transported southward to the Tohoku region (TR). Transport depends largely on the Oyashio, which generally flows southward along the eastern coasts of Hokkaido and Tohoku. Thus, this stock has two different recruitment routes: FB–Doto and FB–TR. In the 1980s, when the southward flow of the Oyashio was strong, the number of age-2 pollock estimated from a virtual population analysis (VPA) indicated that recruitment to the entire stock remained at a medium level. In the 1990s, when the Oyashio weakened, strong year-classes occurred in 1991, 1994, and 1995, but not in the latter half of the 1990s. Juvenile catches in the TR by commercial fisheries, which can be taken as indices of recruitment level via FB–TR, were high during the 1980s and decreased in the 1990s. Although there was no significant difference in the average number of recruits between the 1980s and the 1990s as estimated from a VPA, the recruitment patterns differed between the two decades. Here, we propose that recruitment routes of this stock shifted in response to environmental changes.  相似文献   

Seal sizes and habitat conditions assessed from aerial photography and video analysis     

Estep  Kenneth W.; MacIntyre  Ferren; Noji  Thomad T.; Stensholt  Boonchai; Oritsland  Torger 《ICES Journal of Marine Science》1994,51(3):253-261

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The Ecology of Benthos in the Gulf of ThermaTkos, Greece     

Antonis J.  Zarkanellas Marios E.  Kattoulas 《Marine Ecology》1982,3(1):21-39

Abstract. Benthic samples were taken at 26 stations during a two year period (1975–1977) in the Gulf of Thermaïkos, Greece. The topography and relevant physicochemical characteristics of the area are presented and discussed. Both density and biomass increase towards the northern limits in the Bay of Thessaloniki and in the Gulf of Thermaïkos, the difference between them being the degree of change in a north-south direction. Analyses of the degree of concurrence of the dominant species show the existence of a number of groups of concurrent dominant species with characteristic distributional patterns and differing areal coverage in the study area. The observed quantitative and qualitative differences in the benthos are causally related to the differing environmental conditions prevailing in the two subareas.  相似文献   

Some Considerations in Design and Construction of the Wei-Liu Water Supplying Submarine Pipeline     

Fan Yunlin  Chang Dezhi Associate Professor  Dept. of Ocean Eng.  Tianjin University Engineer  Construction Committee of Weihai City  Shandong Province 《中国海洋工程》1991,(4)

The Wei- Liu water supplying submarine pipeline is at present the longest one of the kind in China. It is about 4 kilometers long from Weihai City to Liugong Island in Shandong province. It took only half a year to design and construct it. The project was of a high economic efficiency and some practical experiences were achieved. In this paper a general introduction to the design and construction of this pipeline is presented and such problems as the stability of the pipeline in very soft clay, design of curved slide for launching and estimation of dragging forces are expounded.  相似文献   

Transient Hydroelastic Response of VLFS by FEM with Impedance Boundary Conditions in Time Domain   总被引：1，自引：1，他引：1  

邱流潮  刘桦 《中国海洋工程》2005,19(1):1-9

A time-dependent finite element method (FEM) is developed to analyze the transient hydroelastie responses of very large floating structures (VLFS) subjected to dynamic loads. The hydrodynamic problem is formulated based on the linear theory of fluid and the structural response is analyzed based on the thin plate theory. The FEM truncates the unbounded fluid domain by introducing an artificial boundary surface, thus defining a finite computational domain. At this boundary surface an impedance boundary conditions are applied so that no wave reflections occur. In the proposed scheme, all of the procedures are processed directly in time domain, which is efficient for nonlinear analyses of structure floating on unbounded fluid. Numerical results indicate acceptable accuracy of the proposed method.  相似文献   

海洋弧菌QJH-12发酵产琼胶酶条件的优化   总被引：1，自引：0，他引：1       下载免费PDF全文

王静雪  江晓路  牟海津  管华诗 《海洋科学》2007,31(7):8-14

从中国南海海域分离到了一株具有较高琼胶降解活性的弧菌Vibrio sp.QJH-12,该菌株为革兰氏阴性菌,呈弯曲杆状,极生单根鞭毛,氧化酶阳性,过氧化氢酶阳性,O/129试验阳性。在琼胶平板上生长可软化琼胶,并在菌落周围产生凹陷。通过单因子实验和正交实验确定了培养基的最佳组成:琼胶2.0‰,柠檬酸三铵1.0‰,K2HPO41.0‰,NaCl1.0%。确定该菌株的最适发酵产酶条件:装液量为250mL的三角瓶中装入125mL的液体发酵培养基,培养基起始pH6.5,摇瓶转速150r/min,30℃发酵培养26h,发酵液的酶活力达到332U/mL。结果表明,该菌株从产酶活力和发酵特点等各方面具备工业化开发的潜力。  相似文献