Onshore scour characteristics around submerged vertical and semicircular breakwaters   总被引：1，自引：0，他引：1  

D. Morgan Young  Firat Y. Testik 《Coastal Engineering》2009

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Two-dimensional,two-phase granular sediment transport model with applications to scouring downstream of an apron     

L.O. Amoudry  P.L.-F. Liu 《Coastal Engineering》2009

We present a two-dimensional, two-phase model for non-cohesive sediment transport. This model solves concentration-weighted averaged equations of motion for both fluid and sediment phases. The model accounts for the interphase momentum transfer by considering drag forces. A collisional theory is used to compute the sediment stresses, while a two-equation (k–ε) fluid turbulence closure is implemented. A benchmark sediment transport problem concerning the scouring downstream of an apron is carried out as an example and numerical results agree with existing experimental data.  相似文献   

Fundamental study for morphodynamic modelling: Sand mounds in oscillatory flows     

P.K. Stansby  J. Huang  D.D. Apsley  M.I. García-Hermosa  A.G.L. Borthwick  P.H. Taylor  R.L. Soulsby 《Coastal Engineering》2009

Experiments on sand mounds in oscillatory flow, undertaken in controlled, large-scale laboratory conditions, have produced well-defined data sets for model comparison. Three bathymetries with different levels of submergence, including a surface-piercing case, were tested. The maximum slope was about 1:5.5. Sediment transport is due to bed load with ripple formation. The principal time-dependent bulk parameters are the vertical distance of the centre of gravity above the base and the volume of the mound. A semi-implicit finite-volume depth-averaged hydrodynamic model is used to drive morphodynamics, using van Rijn's sediment flux model generalized to take account of bed slope, and some justification is given for depth-averaged modeling in these conditions. Starting the model runs with the conditions at the end of the first cycle avoided initial atypical physical behaviour. In general good predictions were obtained with an angle of repose reduced from the standard value of about 30° for stationary beds to 15°. For these situations, morphodynamics was largely unaffected by a hydrodynamic roughness height in the range 2.5D₅₀ to 51D₅₀, with larger values accounting for ripple roughness. The reduced angle of repose may be physically expected with mobile beds but this specific value is only expected to be suited to this form of bed motion. In one case an exaggerated ripple formed near the top of the mound reducing agreement with experiment. For the submerged case with normal ripple structure excellent predictions were obtained. For the initially surface-piercing mound, the time of submergence was better predicted with a 30° angle of repose, presumably due to the prominent influence of the near stationary bed near the wet/dry interface, although long term predictions were better predicted with 15°. The occurrence of vortex shedding in the first cycle modeled was in agreement with experimental observation.  相似文献   

Formula for predicting bedload transport rate in oscillatory sheet flows     

J.P. Le Roux 《Coastal Engineering》2009

The method of Wang [Wang, Y.-H., 2007. Formula for predicting bedload transport rate in oscillatory sheet flow. Coastal Engineering 54, 594–601] to predict the wave friction factor is discussed. At the threshold of sediment entrainment the proposed equation produces a wide scatter of data points when plotted against an equation based on the Shields parameter. It is shown that a better correlation coefficient can be obtained by calculating the critical wave friction factor directly from the wave period, as well as the sediment and water properties.  相似文献   

Seasonal variation of horizontal material transport through the eastern channel of the Tsushima Straits   总被引：2，自引：2，他引：0  

Akihiko Morimoto  Tetsutaro Takikawa  Goh Onitsuka  Atsushi Watanabe  Masatoshi Moku  Tetsuo Yanagi 《Journal of Oceanography》2009,65(1):61-71

We conducted hydrographic observations ten times in the Tsushima Strait to reveal seasonal variations of horizontal material transports such as of heat, freshwater, chlorophyll a, and dissolved inorganic nitrogen (DIN) and phosphorus (DIP) through the eastern channel of the Tsushima Strait (ECTS). The volume, freshwater, and heat transport results are of nearly the same order as results reported in previous studies. The annual mean DIN and DIP transports of 3.59 kmol/s and 0.29 kmol/s are large relative to those of the Changjiang and the Taiwan Strait and are horizontally transported through the ECTS. Nutrient transports are high in July–August and October and low in April and November. Increased nutrient transports in July–August and October are due to the appearance of a cold saline water mass in the bottom layer of the ECTS. Changes in DIN transports in summer and autumn, which account for two-thirds of the total annual DIN transport, would have a large effect on the nitrogen budget and biological productivity in the Tsushima Warm Current region.  相似文献   

Short-term temperature and salinity variations in the Tsushima Strait in 2004: Behavior of the surface low-salinity water in the strait     

Kosuke Mori  Takeshi Matsuno  Tomoharu Senjyu  Naoki Hirose  In-Seong Han 《Journal of Oceanography》2009,65(3):301-310

Temporal variations in temperature and salinity observed in 2004 were investigated on a short time scale in the Tsushima Strait. The data were obtained by long-term in situ measurements at Mitsushima and Futaoi Island using an instrument equipped with a piston-type wiper to avoid biofouling. In addition, the temperature and salinity values of the surface layer obtained by a commercial ferryboat between Hakata and Busan were used to investigate their spatiotemporal variations. Temperature and salinity variations with a time scale of several days had a negative correlation in the summer. This evidence suggests that a warm and less saline water mass, which is considered to be mainly the Changjiang Diluted Water (CDW), flowed intermittently through the Tsushima Strait in summer. In late July 2004, a large low-salinity water mass was detected in the Tsushima Strait. At that time, the freshwater transport through the Tsushima Strait transiently reached about 12 × 10⁴ m³s⁻¹, which is estimated from observed acoustic Doppler current profiler (ADCP) data along a ferryboat line and inferred salinity profiles. This estimated value is more than double the maximum of the climatological monthly mean of the Changjiang discharge. Furthermore, salinity and surface current data obtained by high frequency ocean radar (HF radar) indicate that water properties at Mitsushima may occasionally represent part of the water flowing through the western channel via a countercurrent, although Mitsushima is geographically located in the eastern channel.  相似文献   

Mesoscale physical processes and zooplankton transport-retention in the northern Norwegian shelf region     

Yiwu Zhu  Kurt S. Tande  Meng Zhou 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1922

Northern Norwegian shelf regions are highly productive, supporting fisheries rich in commercially important species such as cod, herring and capelin. It has been long recognized that the mesoscale jets, meanders and eddies associated with interactions between the North Atlantic Current, Norwegian Coastal Current and regional bottom topographic features such as troughs, banks and shelfbreaks play important roles in transporting and retaining zooplankton. To investigate zooplankton distributions and their correspondence with the physical fields, three large-scale surveys with mesoscale resolutions on physical and biological fields were conducted in northern Norwegian shelf regions between latitudes 68°15′N and 70°15′N in springs of 2000–2002. Survey results provide insights into the relationships between zooplankton distributions and the physical features such as fronts, the Norwegian Coastal Current and eddies related to topographic features. The physical and biological data are integrated and analyzed focusing on water types, estimation of geostrophic currents from direct current measurements, along-shelf transport of zooplankton, and retention of zooplankton by the mesoscale meander–eddy over a typical bank area on the shelf. The estimated mean transport in the upper 100 m on the shelf in the survey region is approximately 6.4×10³ tonnes wet weight day⁻¹ northward. High zooplankton abundances were found over both Malangsgrunnen and Sveinsgrunnen banks. The specific accumulation rate from northward–southward transport in the upper 100 m over Malangsgrunnen was approximately 0.08 day⁻¹, while variable currents with an offshore gradient of zooplankton abundance over Sveinsgrunnen implies an offshore dispersion of coastal-originated zooplankton cohort.  相似文献   

源地黑潮及其上下游流量的变化特征   总被引：3，自引：1，他引：2  

蔡榕硕  张启龙  齐庆华 《台湾海峡》2009,28(3):299-307

本文基于长时间序列的海流和温盐资料（最新版SODA高分辩率再分析资料和137°E断面的观测资料）,计算了黑潮流系四个主要断面的流量,并分析了它们的变化特征．结果表明,黑潮流系各主要断面流量具有显著的季节性差异,其年际、年代际变化明显．相关分析表明,源地黑潮及其上下游流量变化具有较强的独立性,变化不尽一致,其中,短期气候变化特征可能与热带太平洋的年际变化有明显关联,而年代际变化则可能与发生于北太平洋的年代际变化以及其它副热带中尺度涡旋等变化有一定联系．  相似文献   

北太平洋波浪输运和西边界流的季节变化     

张坤兰  吴克俭  胡保全  毕凡 《海洋湖沼通报》2009,(4)

西边界流输运可以用Sverdrup理论推算出来.本文首先利用ECMWF再分析风场数据,计算了44年的月平均的风应力旋度及Sverdrup体积输运,在北太平洋3条纬度上对Sverdrup体积输运进行积分,得到Sverdrup体积输运的季节变化,从中发现,在向赤道流动的方向上,Sverdrup体积输运在冬季存在最大值,夏季存在最小值;同样利用ECMWF再分析波浪数据,计算了44a的月平均的Stokes体积输运,在相同纬度上对Stokes体积输运进行积分,得到Stokes体积输运的季节变化,从结果中发现,在向赤道流动的方向上,Stokes输运在冬季存在最大值,在夏季存在最小值.在本文中设定R=T_(st)/T_(sv)×100%,T_(st)为Stokes体积输运,T_(sv)为Sverdrup体积输运,发现Stokes输运和Sverdrup输运存在同位相的季节变化,并且(-R)冬季平均值在5%以上,年平均值在2%～3%左右,从而推断出波浪诱导的输运对Sverdrup输运,既对西边界流有不可忽视的贡献.  相似文献   

Modeling Arctic Ocean heat transport and warming episodes in the 20th century caused by the intruding Atlantic Water     

Jun Takahashi  Tatsuo Suzuki  Igor V Polyakov  Kohei Mizobata  Moto Ikeda  Fancois J.Saucier  Markus Meier 《极地研究(英文版)》2008,19(2):159-167

This study investigates the Arctic Ocean warming episodes in the 20th century using both a high-resolution coupled global climate model and historical observations. The model, with no flux adjustment, reproduces well the Atlantic Water core temperature （AWCT） in the Arctic Ocean and shows that four largest decadalscale warming episodes occurred in the 1930s, 70s, 80s, and 90s, in agreement with the hydrographic observational data. The difference is that there was no pre-warming prior to the 1930s episode, while there were two pre-warming episodes in the 1970s and 80s prior to the 1990s, leading the 1990s into the largest and prolonged warming in the 20th century. Over the last century, the simulated heat transport via Fram Strait and the Barents Sea was estimated to be, on average, 31.32 TW and 14.82 TW, respectively, while the Bering Strait also provides 15.94 TW heat into the west- ern Arctic Ocean. Heat transport into the Arctic Ocean by the Atlantic Water via Fram Strait and the Barents Sea correlates significantly with AWCT （ C = 0.75 ） at 0- lag. The modeled North Atlantic Oscillation （NAO） index has a significant correlation with the heat transport （ C = 0.37 ）. The observed AWCT has a significant correlation with both the modeled AWCT （ C =0.49） and the heat transport （ C =0.41 ）. However, the modeled NAO index does not significantly correlate with either the observed AWCT （ C = 0.03 ） or modeled AWCT （ C = 0.16 ） at a zero-lag, indicating that the Arctic climate system is far more complex than expected.  相似文献