A phase-resolving cross shore sediment transport model for beach profile evolution     

K. A. Rakha  R. Deigaard  I. Brker 《Coastal Engineering》1997,31(1-4)

A phase-resolving wave transformation module is combined with an intra-wave sediment transport module to calculate the on-/offshore sediment transport rates. The wave module is based on the Boussinesq equations extended into the surf zone. The vertical variation of the mean undertow and the intra-wave sediment concentrations are calculated. The net sediment transport rates are calculated, and the equation for conservation of sediment is solved to predict the beach profile evolution. The results of the present paper showed that the undertow contribution to the sediment transport rates is not dominating in all parts of the surf zone, even for eroding beaches, suggesting that other contributions should not be neglected. The present model also showed that for the same offshore wave energy the time series of the oscillatory motion is important and that the effect of wave groups cannot be disregarded.  相似文献   

石斑鱼虹彩病毒SGIV在宿主细胞内依赖微管运动的行为特征     

王立群  王劭雯  王宏达  秦启伟 《热带海洋学报》2020,39(1):66-73

病毒是非常微小的简单生物, 不能独立生存, 必须借助宿主细胞完成自身的繁衍。病毒侵染进入细胞后, 通常借助于微管通过黏稠的细胞质运动到特定的复制位点。然而, 有关病毒依赖微管运动行为的精细动态研究还比较少。石斑鱼虹彩病毒(Singapore grouper iridovirus, SGIV)为虹彩病毒科蛙病毒属的一个新种, 是海水养殖鱼类的重要病毒性病原, 对海水养殖业造成重大经济损失。利用单粒子示踪技术实时追踪了SGIV病毒粒子沿微管运动的行为, 观察到SGIV在细胞边缘至微管中心之间的双向运动, 最高瞬时速度约0.2μm·s^-1, 均表现为主动运输。病毒粒子运动至微管交叉位置会减速迂回, 而后或受限于此, 平均运动速率约0.008μm·s^-1, 或通过交叉处继续快速运动, 最高瞬时速度为0.2μm·s^-1。同时, SGIV感染会影响微管的形态结构, 随着SGIV感染, 微管逐渐围绕细胞核和病毒加工厂形成环状结构。研究结果初步揭示了SGIV病毒和细胞微管之间相互作用的复杂过程, 丰富了我们对虹彩病毒胞内生命活动的认识, 有助于深入地理解海水鱼类虹彩病毒感染致病机理。  相似文献   

The combined effect of transport and temperature on distribution and growth of larvae and pelagic juveniles of Arcto-Norwegian cod   总被引：5，自引：0，他引：5  

Vikebo  Frode; Sundby  Svein; Adlandsvik  Bjorn; Fiksen  Oyvind 《ICES Journal of Marine Science》2005,62(7):1375-1386

  相似文献   

南海北部海区水团的判别分析   总被引：1，自引：0，他引：1  

李凤岐  苏育嵩  范立群 《中国海洋大学学报(自然科学版)》1989,(Z1)

将判别分析应用于南海北部海区的水团分析。划分为八个水团:沿岸冲淡水团(F),近岸混合水团(M),暖表层水团(WS),表层水团(S),表—次层混合水团(SU),次层水团(U),次—中层混合水团(UI)和中层水团(I)。给出了各水团在四季代表月的Bayes多组判别的系数和参数。用资料检验判别的成效.冬季和春季可达95.90％以上,夏季为94.80％,秋季是全年最低值,为92.72％。讨论了造成错判的原因,并与Fisher判别作了比较。当测值维数较低时,建议选用Bayes判别。对八个水团以及各水团两两之间差异的显著性进行了检验,证实在每个季节中各水团之间的差异,都在高度置信水平(α=0.01)上具有显著性。因而,划分为八个水团是有实际意义的,其判别式的系数和参数,可用于实际的判别和预报。  相似文献   

A Numerical Model for Natural Backfill of Pipeline Trenches Subjected to Unidirectional／Oscillatory Flows     

LIANGDong-fang CHENGLiang KervinYEOW 《中国海洋工程》2005,19(2):269-286

A numerical model for the self-burial of a pipeline trench is developed. Morphological evolutions of a pipeline trench under steady-current or oscillatory-flow conditions are simulated with/without a pipeline inside the trench. The oscillatory flow in this study represents the action of waves. The two-dimensional Reynolds-averaged continuity and Navier-Stokes equations with the standard k-e turbulence closure, as well as the sediment transport equations, are solved with the finite difference method in a eurvilirrear coordinate system. Both bed and suspended loads of sediment transport are included in the morphological model. Because of the lack of experimental data on the backfilling of pipeline trenches, the numericalmodel is firstly verified against three closely-relevant experiments available in literature. A detailed measurement of the channel migration phenomenon under steady currents is employed for the assessment of the integral performance of themodel. The two experimental results from U-tube tests are used to validate the model‘s ability in predicting oscillatory flows. Different time-marching schemes are employed for the morphological computation under unidirectional and oscillatory conditions. It is found that vortex motions within the trench play an important role in the trench development.  相似文献   

胶州湾泛亚码头疏浚方案优选及悬浮物影响预测     

李铁军  孙英兰  刘伟峰  付会 《海洋湖沼通报》2007,(4):144-150

采用有限元分步杂交方法,在已建潮流场的基础上,建立了胶州湾疏浚物悬浮泥沙的二维输运-扩散模型,并应用于胶州湾前湾港区泛亚码头工程疏浚区的疏浚物输运扩散的数值模拟预测。根据预测结果分析了泛亚码头疏浚区施工期间悬浮泥沙对附近海域水环境和生态环境的影响,并对不同的疏浚方案进行了优选。  相似文献   

山东荣成湾月湖口门落潮干道的推移质输运   总被引：6，自引：2，他引：6  

薛允传  高抒  贾建军 《海洋与湖沼》2002,33(4):356-363

改进了Gao等 ( 1 994)方法 ,并用以计算潮汐汊道口门落潮干道的垂线平均流速。利用月湖潮汐汊道系统冬、夏季各一个月的潮位资料 ,计算落潮干道的潮流流速和推移质输运率。结果表明 ,流速的计算值和实测值呈良好的相关性 ,落潮干道内落潮流的输沙能力高于涨潮流输沙能力  相似文献   

Coral Recruitment and Regeneration on a Maldivian Reef 21 Months after the Coral Bleaching Event of 1998     

Karen Loch  Wolfgang Loch  Helmut Schuhmacher  Wolf R. See 《Marine Ecology》2002,23(3):219-236

Abstract. This paper describes the quantitative inventory of stony corals on a Maldivian reef after the bleaching event of 1998. The detailed data, collected in March 1999 and March 2000, comprise survival, new recruitment and regenerates. They were obtained in 6 transects laid out randomly on the reef flat, on 22 Acropora tables on 6 sites at the reef edge and on 39 Porites lobata blocks and 1 Diploastrea heliopora colony. The present cover of living zooxanthellate corals is reduced to ca. 2 – 5 % of its previous state. Acroporidae and Pocilloporidae were practically wiped out, while Poritidae survived partly and Agariciidae (esp. Pavona) are now the dominant group. New settlements on dead Acropora tables were mainly Agariciidae, followed by Acroporidae and Pocilloporidae. Regenerates on Porites were pronounced and the apparent yearly increase in mass was about threefold that of Diploastrea, which is 3 – 4 mm per year. The influence on reef ecology in terms of coral substrate and species, possible sources of larvae, change of guilds in reef builders, other species and the prospect for further development of the reef, with respect to growth versus erosion, is discussed.  相似文献   

Calculation of the added mass of circular cylinders in shallow water     

David Clarke   《Ocean Engineering》2001,28(9):354

The added mass of hull section shapes must be known, in order to carry out any studies of ship motions, which may be associated with either seakeeping or manoeuvring. Determination of the added mass in deep water can involve conformal mapping or surface singularity distributions. However, in shallow water the problem of determining the added mass is made more difficult by the proximity of the seabed. In this paper, three approaches to the problem of finding the added mass of semi-circular sections are explored. Although there is no known exact solution to this problem, the relationships given by the three methods are compared and the approximate nature of the solutions is examined. The first method is a series solution, which is taken here to include more terms than are normally given in the existing literature. The other two solutions are considered to be new, and so are given in some mathematical detail.  相似文献   

2021年10月山西一次罕见持续性强降水过程物理机制分析     

乔钰  赵桂香  王妍 《沙漠与绿洲气象(新疆气象)》2024,18(2)

利用气象观测资料、NCEP/NCAR 1°×1°再分析资料以及GDAS资料,对2021年10月2-7日山西持续性强降水天气过程进行分析。结果表明：稳定的乌拉尔山低槽后部冷空气扩散,中纬度短波槽东移,与副热带高压外围西南暖湿气流持续交汇,同时高低空急流耦合形成强烈上升运动,低层切变线和地面辐合线稳定维持,及低层水汽不断输送并形成辐合,为持续性强降水的发生发展提供有利动力和水汽条件。此次强降水过程分为对流性降水和稳定性降水2个阶段,2阶段水汽输送通道的源地、路径、高度均有明显差异,但水汽输送贡献率均以对流层中低层山西南侧的水汽输送占主导地位。降水开始前,对流层中上层存在对称不稳定,大气可降水量明显跃增;对流性降水阶段,干空气不断入侵,对流不稳定快速建立与释放,对流层中低层水汽辐合区与强上升气流配合,导致山西出现强对流天气。地形的阻挡、抬升及地形收缩作用,对局地极端强降水具有增幅作用。  相似文献