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1.
The phase one project of the twin jetties at the Tao-er Estuary yields no effect on the flow, and there is a large area of deposition. A numerical model is employed to simulate the flow field, and the scouring and silting in the channel be-tween the two jetties are analyzed. The results show that the effective tidal flux between the two jetties is reduced due to the notch located at the heel of the east jetty, and the effect of contraction-flush is not obvious. As for the regulation of this kind of estuary under the tide action, the capability of tidal flux should be fully used. 相似文献
2.
Naoki Hirose 《Journal of Oceanography》2011,67(3):323-336
Significant impacts of the subgridscale parameterizations have been emphasized in modeling the ocean circulations, but various
different parameter values are applied to similar numerical studies often without any justification. This study objectively
estimates a set of empirical parameters along with their uncertainty for circulation modeling of the East Asian Marginal Seas.
The solutions for 14 major parameters are obtained by using model Green’s functions with constraints of climatological temperature
and salinity data. The largest cost function reduction occurs in the eastern Japan Sea associated with the sharp gradient
of the Polar Front. The calibrated parameters are also validated with realistic transport and path of the Kuroshio in the
final experiment. The inverse estimation shows that freshwater discharges from small rivers can be attributed to the coastal
precipitation over a strip of land 74–81 km wide. The thickness diffusion coefficient may be similar to the isopycnal and
horizontal diffusion coefficients in their magnitude. The accelerated initial condition also contributes to the cost function
reduction resulting in weaker trends of deep temperature. Most importantly, estimated scaling factors suggest a significant
reduction of the reanalyzed wind stress data for more realistic ocean circulations. Possible reasons for the momentum missing
are also discussed. 相似文献
3.
4.
This paper presents safety evaluations of jetties found on soft clays at Huanghua Port to protect the channel from deposition due to long shore transport. It is likely to be the most critical for the jetties during construction, as far as excess pore water pressure and its effects on the embankment stability are concerned. A rubble mound jetty and a caisson jetty are considered as design alternatives for comparison. Finite element analysis and limit equilibrium analysis are carried out to evaluate the stability of the jetties during construction. For the rubble mound jetty, effective stresses in the soft clays are calculated associated with consolidation, so as to estimate the shear strength increased thereby. With the effective stresses and shear strength, the critical situation of the rubble mound jetty is revealed by the limit equilibrium analysis. For the caisson jetty, wave action is concerned, which is transformed into distributed forces on the caisson. Both the finite element analysis and the limit equilibrium analysis indicate a potential general shear failure of the caisson jetty and the foundation. 相似文献
5.
基于非结构有限体积法海洋模型FVCOM(Finite-Volume Community Ocean Model), 建立了马六甲海峡及其毗邻海域高分辨率水动力数值模型, 研究了风和潮流作用下的余环流结构以及水体输运特征。结果表明, 马六甲海峡航道中央潮流运动以往复流为主, 边缘存在旋转流; 主要研究区域内落潮流速略大于涨潮流速, 东南窄道处流速最大; 因峡道束窄变浅, 在涨落潮过程中潮流发生汇聚与分离; 主要研究区域东南段存在3个显著的潮致余环流; 东北季风驱动时模型响应为海峡海流整体向西北方向流动, 西南季风时反之; 季风期间潮致表层余环流结构被破坏, 但底层余流仍存在水平环流结构, 且随着风速增加, 底层余环流的数目、大小、形状、位置均会产生变化; 季风过渡期余环流结构也会发生部分改变, 尤其是小潮期间风场影响效果显著。 相似文献
6.
In order to confirm the results of the authors’ previous work, which found that the existence of disturbances smaller than
meso-scale eddies is important in large-scale mixing process between the Oyashio and Kuroshio waters in the intermediate layer,
the results of an eddy-resolving model experiment are analyzed and compared with those of an eddy-permitting model. The intermediate
salinity minimum given in the initial condition weakens as integration advances in the eddy-permitting model, while it recovers
rapidly and is maintained thereafter in the eddy-resolving model, initialized from the unrealistic salinity distribution of
the former. Filament-like fine structures in temperature and salinity develop actively in the latter, which are much smaller
in horizontal width than meso-scale eddies, suggesting the importance of such disturbances in the large-scale mixing. The
mixing ratio of the Oyashio water defined by the original Oyashio and Kuroshio waters shows that its value is generally higher
in the intermediate lower sub-layer than in the intermediate upper sub-layer in the Mixed Water Region, and the salinity minimum
exists between layers with low and high values of the mixing ratio with its strong vertical gradient. The eddy transports
of the Oyashio and Kuroshio waters in an isopycnal layer are divided into four components, usual isopycnal mixing of temperature
and salinity being dominant, followed by the component associated with the thickness flux. The southward eddy transport of
the Oyashio water and the northward eddy transport of the Kuroshio water are not symmetric to each other because the thickness-flux-associated
components are in the same direction (southward). 相似文献
7.
Seasonal variation of the water circulations in the East China Sea and the Yellow Sea is investigated with use of a robust diagnostic numerical model. Water circulations in four season are calculated diagnostically from the observed water temperature and salinity data from JODC (Japan Oceanographic Data Center) and wind data from COADS (Comprehensive Ocean-Atmosphere Data Set). Counter-clockwise circulations are developed at the upper and middle layers and a clockwise one at the lower layer in the central part of he Yellow Sea in summer. On the other hand, a clockwise circualtion is developed from the surface to the bottom in the Yellow Sea and a counter-clockwise one in, the northern part of the East China Sea in winter. 相似文献
8.
Christian Ferrarin Georg Umgiesser Marco Bajo Debora Bellafiore Francesca De Pascalis Michol Ghezzo Giorgio Mattassi Isabella Scroccaro 《Estuarine, Coastal and Shelf Science》2010
The hydraulic regime-based zonation scheme of the Lagoons of Marano and Grado (Italy) has been derived by means of numerical models. A finite element modelling system has been used to describe the water circulation taking in account different forces such as tide, wind and rivers. The model has been validated by comparing the simulation results against measured water levels, salinity and water temperature data collected in several stations inside the lagoons. The analysis of water circulation, salinity and spatial distribution of passive tracers released at the inlets, led to a physically-based division of the lagoons system into six subbasins. The derived classification scheme is of crucial value for understanding the renewal capacity and pollutants distribution patterns in the lagoon. 相似文献
9.
采用三维潮流温盐数学模型对六横岛附近海域的水动力环境及盐度场分布进行数值模拟,并以实测资料进行验证,所建立模型可以较好地反映该海域潮流动力特征及盐度场的分布情况。利用验证后的三维数学模型,对海水淡化工程浓盐水排放后盐度场分布进行计算,将排放后的盐度分布与工程前进行对比分析,并推算盐升面积及垂向盐度增量。结果表明,海水淡化工程排放的浓盐水对六横岛海域盐度分布的影响主要集中在排水口附近的底层,影响区域呈带状分布,最大盐度增量为1.2左右,且排水口附近海域出现盐度垂向分层。 相似文献
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11.
The seasonal circulation in the southeastern Huanghai Sea has been studied with hydrographic data,which were observed in February and June 1994 and bimonthly during 1970-1990,and numerical model results.Horiwntal distributions of temperature and salinity in 1994 are quite different due to strong tidal mixing so that we need a analysis to see the real distributions of water masses.The mixing ratio analysis with the data of 1970-1990 shows the connection of the waters in the west coasts of Kotea Peninsula with warm and saline waters from the south in summer,which means northward inflows along the west coasts of Korea Peninsula in summer.With this flow,the seasonal circulations,which are deduced from the seasonal change of water mass distributions in the lower layer,are warm inflows in winter and mld outflows in summer in the central Huanghai Sea,and cold outflows in winter and warm inflows in summer along the west coasts of Korea Peninsula.The seasonally changed inflows might be the Huanghai Sea Warm Current.The monsoon winds can drive such circulations.However,summer monsoon winds are weak and irregular.As one of other possible dynamics,the variation of Kuroshio transport is numerically studied with allowing sea level fluctuations.Although it should be studied more,it possibly drives the summer circulations.The real circulations seem to be driven by both of them. 相似文献
12.
河口整治工程建筑物局部冲刷试验研究 总被引：3，自引：0，他引：3
采用正态系列模型延伸法,通过试验研究了长江口深水航道治理一期工程丁坝坝头、北导堤头部的局部冲刷深度和范围,试验结果预报了丁坝坝头和北导堤头部的冲刷深度,并得出了合理的防护范围,随着长江口深水航道治理工程实施,试验结果得到较好的实践检验。分别采用稳定流和潮汐往复流试验方法,比较了不同试验水流条件的丁坝坝头冲刷深度,通过原型沙和轻质沙的比较试验,比较了系列模型延伸法采用不同模型沙得出试验结果。 相似文献
13.
A three-dimensional semi-implicit finite volume numerical model has been developed and applied to study tidal circulation and salinity stratification in the region of Oujiang River Estuary, China. The model employs horizontally unstructured grids and boundary-fitted coordinate system in the vertical direction. Governing equations consisting of continuity, momentum, and transport equations are all solved in the integral form of the equations, which provides a better representation of the conservative laws for mass, momentum, and transport in the coastal region with complex geometry and bottom bathymetry. The model performance was firstly quantified with skill assessment statistics on the choice of different parameters and validated with observed tidal elevation, current velocity, direction and salinity data over a spring–neap tidal cycle collected in 2006. Numerical results show that the model with wetting–drying capability successfully simulated the tidal currents and salinity fields with a reasonable accuracy and indicate that the Oujiang River Estuary is a macrotidal estuary with strong tidal mixing. In addition, the model results also show that the Oujiang River Estuary is a well-mixed estuary during spring tide. Then, the numerical simulations were performed to compare the hydrodynamic process and salinity distribution before and after a river training, which was conducted by blocking the south branch of the Oujiang River mouth. The results reveal that with the only north access to the sea, the influence of the blocking project on the flood discharge capacity is limited and the incremental velocity is beneficial to the navigation channel maintenance, although it will cause some scour to the embankment. Furthermore, the redistribution of tidal prism passing in or out the north branch makes a little severe salinity intrusion during high tide or low tide. However, the salinity intrusion is still within acceptable range, although it can cause some adverse effect on water intaking of production and life. The variations of salinity levels in Yueqing Bay situated at the north of the river mouth are not obvious, so the blocking project will not bring damage to local aquiculture. However, significant changes of salinity happen inside or outside of the south branch, so enough attention need to be paid to the changes of environment caused by the salinity variation after the blocking project. Overall, by weighing advantages and disadvantages of the blocking project, it is feasible and the model can be considered as a tool for managing and studying estuarine circulation. 相似文献
14.
本文应用ECOM模式,设计1个控制试验,研究理想河口环流和盐水入侵的动力过程.数值计算结果表明,盐水入侵产生盐度锋面,在锋面处底层存在着向陆的密度流,为保持断面上质量连续,上层的流速趋于增大;近口门附近底层流有偏南分量,表明有横向环流存在.在口门外因斜压和底形的作用,产生明显的上升流.盐水入侵在空间上具有不对称性,高盐水位于北岸的下层.在拦门沙上游出现上下2个相反方向的横向环流,而在口门处只出现1个顺时针方向的横向环流.从动力机制上分析了盐水入侵的空间不对称性和横向环流的产生. 相似文献
15.
J. E. W. WICHERS 《中国海洋工程》1999,(1)
—Most terminals for tankers are piers and sea islands,while other types include single pointmoorings and multiple-buoy moorings.The LNG and LPG carrier moored to the jetty is a very commonterminal for transfer of gas in open seas.It is important to estimate the motions and line tensions of theLNG carrier when it moors to a jetty in metocean environment.Normally,the motions of the LNG carrierwould be restricted by the loading arm,which is connected to LNG carrier＇s manifold.An example of125,000m~3 LNG carrier moored to a jetty exposed to a set of environment conditions is given.Amathematical model which is based on the equations of motion in the time domain is used to the analysisof LNG moored to an offshore jetty exposed to waves,swell,wind and current.By means of a time do-main computer program TERMSIM computations are carried out to determine and optimize the lay-outand/or orientation of the jetty and mooring gear in terms of forces in mooring lines and fenders and theenvelope of motions of the loadi 相似文献
16.
Hu Yuchu Wu Shaozhang Lu Liyun Senior Engineer Nanjing Hydraulic Research Institute Nanjing
Professor Senior Engineer Nanjing Hydraulic Research Institute Nanjing
Assistant Engineer Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1992,(4)
The concrete blocks used on a jetty in Shanghai were made in 1909 and 1910. Having been exposed in nature for 80 years, now there are 4600 pieces of blocks left on the jetty. Comprehensive inspections, such as external appearance examination, core-drilling of concrete blocks, ultrasonic detection, nuclear densimeter inspection and in-door and out-door chemical analysis, show that 75% of the blocks are of the rebound number of 21 - 23, and the saturated limit compressive strength and dry limit compressive strength of 10MPa; the carbonized depth of concrete is 1 - 2 mm. Compared with the state of the jetty in 1968, already used for 60 years then, the jetty is expected to serve another 40 years or more after being repaired. 相似文献
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18.
Roberta LasagnaMonica Montefalcone Giancarlo AlbertelliNicola Corradi Marco FerrariCarla Morri Carlo Nike Bianchi 《Estuarine, Coastal and Shelf Science》2011,94(3):255-262
While coastal management activities have long been known to exert a strong influence on the health of marine ecosystems, neither scientists nor administrators have realized that small interventions may lead to disproportionately larger impacts. This study investigated the broad and long-lasting environmental consequences of the construction of an ill-planned, although small (only 12 m long) jetty for pleasure crafts on the hydrodynamic conditions and on the meadow of the seagrass Posidonia oceanica of an embayed cove in the Ligurian Sea (NW Mediterranean). There, P. oceanica used to develop on a high (>1.5 m) matte (a lignified terrace causing seafloor elevation) in which the leaves reach the surface and form a compact natural barrier to waves in front of the beach. Such a so-called ‘fringing reef’ of P. oceanica is today recognized of high ecological value and specific conservation efforts are required. The construction of the jetty implied the cutting of the matte, which directly destroyed part of the fringing reef. In addition, meadow mapping and sedimentological analyses coupled with morphodynamic modelling showed that the ecosystem of the whole cove had been greatly altered by the jetty. We used the geometric planform approach, a proper tool in the study of headland-controlled embayment, both to characterise the present situation of Prelo cove and to simulate the original one, before the jetty was built. In the long term, such a small jetty completely altered the configuration and the hydrodynamic conditions of the whole cove, splitting the original pocket beach into two smaller ones and creating strong rip-currents flowing seaward along the jetty. These rip-currents enhanced erosion of residual shallow portions of the meadow and further modified the sedimentary fluxes in shallow waters. A century after the construction of the jetty, an irreversible environmental damage has occurred, as the slow growing rate of P. oceanica implies that the high matte terrace and the fringing reef will hardly form again, even after the removal of the jetty. The lesson learnt from this study is that even such small, and therefore reputed intrinsically ‘innocent’, interventions on the coastal zone require accurate planning based on interdisciplinary studies to understand and respect the delicate interplay among morphological, hydrodynamic and ecological components. 相似文献
19.
借助于六套海洋模式资料,本文初步分析了热带西太平洋深层环流的基本特征。与气候态数据集WOA13相比,水深3000m层除HYCOM以正温度偏差为主外,其余模式均为负温度偏差,且随着深度增加偏差幅度变大。盐度偏差方面,HYCOM和OFES以正偏差为主,其余模式以负偏差为主。温盐偏差在各个深海海盆中的时间变化趋势不尽相同,且与实际观测结果存在较大差异。水深1000—3000m以纬向东西向交替变化的射流为主。3000—5000m的纬向流速减小,形成海盆内环流,不同海盆之间可通过深水通道进行海水交换。3000m以深的关键深海通道的输运通量存在明显的季节变化,甚至不同季节流向也不一致,而海盆内的环流形态受制于位涡收支积分约束方程,进而也表征出季节变化的特征,即不同季节海盆内的环流主要旋转形态不同。在分析了初始温盐场、潮汐及其他要素对深海环流的影响后,本文为日后构建适合热带西太平洋深海环流研究的模式提供了建议。 相似文献
20.
A. E. Gledzer E. B. Gledzer A. A. Khapaev O. G. Chkhetiani 《Izvestiya Atmospheric and Oceanic Physics》2017,53(6):579-591
This paper presents the results of experiments in a circular stationary and rotating channels with thin layers of conductive fluid for configurations consisting of a large number of permanent magnets and providing the MHD generation of small-scale velocity fields. The alternating radial configurations of magnets were chosen in such a way as to ensure the conservation of a discrete symmetry of their mutual arrangement relative to rotations of the circular channel around a central axis and were formed on the basis of numerical calculations with the shallow-water equations. Both in numerical and laboratory experiments, large-scale nearly circular vortices were obtained as a result of the energy transfer from the system of externally generated small-scale vortices to large-scale velocity fields (inverse cascade) under the influence of the Coriolis force in the rotating case. Single large-scale vortices and wide jet streams appear in subrotation and superrotation modes relative to external rotation, depending on its angular velocity. Rotation in a nearly circular vortex has a differential character with a decrease in the angular velocity of rotation with the radius in most area of the channel. 相似文献