黄河入海泥沙在渤海中悬移输送季节变化的数值研究

利用实际的风场和地形等条件,基于一个浪流耦合模型提供的动力场驱动一个悬沙输送模型,研究黄河入海泥沙在渤海中悬浮输运的季节变化特征.通过数值计算发现,69%的黄河入海泥沙最终滞留在滨海区,输往外海的泥沙占入海泥沙总量的31%,尚有4%的泥沙通过渤海海峡输往北黄海.因此,黄河口附近的悬沙含量非常高(≥1kg/m3),且其季节变化主要受到入海水沙通量多寡的影响,丰水丰沙的夏秋季最高.除黄河口外,渤海其他海域海水中悬浮体含量的平面分布具有明显的地区性和季节性,其基本趋势是悬浮体含量随离岸距离的增加而减少,且其季节变化主要受风场时变控制.数值计算得到的悬沙输运年平均结构显示:黄河入海泥沙部分输向渤海湾南岸;而大部分泥沙向东南输向莱州湾,大量泥沙并不在此沉积,继而向东北方向输运,莱州湾只是一个向外输沙的通道.泥沙输运通量的结构与海底冲淤之间有良好的对应关系,最具典型代表性的是黄河口南北两侧涡状通量以及与之对应的泥质沉积区.     

调水调沙影响下黄河口泥沙异重流过程

利用黄河干流大型水库进行调水调沙,在短期内将大量沉积物快速输送入海,是河口泥沙异重流触发的重要窗口期。根据2010年调水调沙期间黄河口沉积动力现场观测资料,建立覆盖整个渤海海域的ROMS数学模型,以黄河利津站逐日水沙数据和海域潮汐、风场数据作为模型驱动条件,模拟调水调沙期间的河口泥沙异重流发育过程。模拟结果显示,在没有大风扰动的情况下,河流入海悬沙浓度29.0 kg/m~3时会在河口产生高密度泥沙异重流。黄河冲淡水携带大量悬浮物从河口流出后,与海水迅速混合,在潮流影响下,冲淡水舌随时间由西北向东南偏转,输运至莱州湾西侧。淡水和沉积物主要以表层羽状流和底层异重流形式输运:表层羽状流扩展范围较大,输运路径为河口西北方向-远岸(河口东北区域)-莱州湾西侧;底层异重流扩散范围较小,输运路径为河口西北方向-河口沿岸(东)-莱州湾西侧。河口泥沙异重流生消和水体垂向结构存在周期性变化特征:落潮时段异重流发育较好,水体层化增强;涨潮时段异重流逐渐消亡,水体混合增强。估算出黄河口清水沟清8叉流路主泓区内水体由河口径流、潮汐应变和潮汐搅动引起的势能变化率,其中潮汐应变和潮汐搅动起主导作用,比河口径流引起的势能变化率高出2～3个数量级(102～103)。     

黄河口门位置及入海径流变化对莱州湾盐度分布的影响

2020年黄河丰水期入海径流量是往年平均值的2倍以上,必然会引起河口水动力和盐度分布的动态变化。本作者基于有限体积海岸海洋模型(Finite Volume Community Ocean Model, FVCOM),模拟2020年黄河冲淡水在丰水期和枯水期的扩散情况,研究黄河口以及莱州湾海域的盐度分布状况变化,以及径流量变化和口门变迁对黄河冲淡水扩散的影响,模型结果与观测结果吻合较好。模拟结果表明,黄河口西北侧潮流沿岸线方向,随着涨落潮呈西北-东南向往复;黄河口以南包括莱州湾的潮流均随着涨落潮呈东北-西南方向往复。高流速区域主要集中在黄河口和莱州湾北部,在0.5m/s以上。在余流作用下,大量的黄河冲淡水会涌入莱州湾,丰水期时27psu等盐线包络面积占到整个莱州湾的1/4左右。径流量和风的变化主要影响羽流的扩散面积,而口门的变迁会改变其扩散方向。黄河冲淡水经北向口门入海主要影响莱州湾区域,经东向口门入海更多地会向北扩散。通过对2020年黄河口及莱州湾海域盐度分布的分析,为黄河入海径流管理及莱州湾渔业资源保护提供科学参考。     

黄河调水调沙期间黄河入海水沙的扩散与通量

以2007年夏季黄河调水调沙期间黄河三角洲海域3断面连续站及渤海南部24个大面站观测的流场、温度、盐度及含沙量资料为依据,分析了调查区水沙扩散特征,计算了各连续站的拉格朗日余流及泥沙输送单宽通量。结果表明,黄河入海泥沙扩散范围非常有限,主要分布在南至莱州湾西南部、北至北纬38°附近离岸约20km以内的带状沿岸区域;但黄河冲淡水出现大面积扩散,覆盖了整个莱州湾的北部和中部,最远可至龙口附近,黄河入海水沙扩散不同步。在现行河口和钓口流路废弃河口存在两个高浓度泥沙中心,分别对应于黄河入海泥沙和废弃钓口流路海域底质再悬浮产生的两个泥沙来源。河口及三角洲近岸切变锋的阻隔及辐聚作用,是大部分黄河入海泥沙沉积在河口及沿岸13m水深以内的主要动力因素。受余流方向及水体垂向湍动较弱的影响,两个高浓度泥沙中心很少有泥沙交换。冲淡水的大面积扩散主要受表层余环流的影响。余流及悬浮泥沙通量计算显示,夏季黄河入海水沙在近岸主要向东北方向扩散。     

黄河口滨海区冲淤演变与潮流不对称

涨落潮不对称是河口滨海区流场的重要特征,在泥沙输运和地貌演变过程中扮演着重要的角色。本文基于实测水深地形、沉积物粒度、水文泥沙观测等资料,分析了黄河口滨海区的冲淤变化、泥沙输运和沉积物特征。同时,本文利用Delft 3D模型模拟了黄河口滨海区的流场,并计算了不同条件下涨落潮流速的不对称分布,结合上述分析,探讨了黄河口滨海区冲淤演变的动力机制。结果表明:现行黄河口至莱州湾滨海区相间分布多个淤积和侵蚀中心;黄河口滨海区存在显著的涨落潮流速不对称现象,现行河口外为涨潮优势流分布区,并呈舌状向南部莱州湾方向伸展,而近岸和莱州湾则普遍为落潮主导;黄河口滨海区的冲淤变化很大程度上受涨落潮流速不对称空间分布及涨落潮优势流转换所控制;强北风作用增强和扩展涨潮优势,促使莱州湾淤积和沉积物粗化。     

广利港海域悬沙分布及黄河口泥沙扩散对其影响

基于遥感影像资料和实测水文泥沙资料,对广利河口海域悬沙分布特征和黄河口入海泥沙扩散进行了分析研究.结果得出,在一般天气情况下,广利港海域工程海域含沙量比较低(＜0.1 kg/m3),黄河口泥沙向南直接扩散距离为10～20 km,对工程区无直接影响,但是在大风天气下,广利河口附近海域含沙量会增高至0.5 kg/m3以上,黄河口入海泥沙扩散向南可达30～40 km,最远可达小清河口,对工程区则有一定的影响;从广利港海域含沙量、底质特征、冲淤性质上来看,黄河口泥沙扩散对工程区是有限的,造成航道和港池淤积的主要泥沙来源为风浪和潮流作用下就地泥沙的搬运输移;黄河入海泥沙呈减小趋势,黄河改由“清8断面”入海,黄河入海泥沙浑水主轴线与广利港的距离增加,对工程区的影响趋于减小.     

基于遥感反演的莱州湾悬沙分布及其沉积动力分析

选用1986-2004年不同时期的LandsatTM/ETM+影像,利用2004年黄河口附近实测数据推导的表层悬浮泥沙浓度反演模型,结合水文气象资料、多年水深数据和极端天气数模结果,研究了莱州湾西南近岸海域表层悬浮泥沙分布特征,结果表明,受黄河丰枯水期的影响,莱州湾西南部海域悬浮泥沙高浓度区主要分布于黄河口附近海域和西南沿岸,其枯水期的覆盖范围一般大于丰水期的。受潮流高流速场控制,黄河口外悬沙浓度高值区与海底泥沙堆积区对应较好,泥沙主要来源于陆源输沙和泥沙再悬浮;在西南近岸浅海区悬沙浓度高值区主要形成于泥沙的再悬浮,在近岸出现轻微冲刷。风等其他海洋动力因素,一般情况下对悬浮泥沙扩散的程度和范围具有一定的影响作用,但悬沙受潮流场影响而形成的总体扩散趋势未发生改变;极端条件下,风暴潮流使莱州湾西南部近岸浅海区的悬浮泥沙浓度显著增加。     

黄河入海径流对河口海域盐度影响研究

为研究黄河入海径流变化条件下河口附近海域盐度扩散特征,以更好地保护河口海域生物资源多样性,本文以黄河下游利津水文站的长序列实测径流数据资料为基础,利用近海水动力模型FVCOM,分析径流变化对黄河口海域盐度的影响规律。结果表明：黄河口与莱州湾之间存在顺时针的环流系统,在余流作用以及涨落潮方向的影响下,黄河冲淡水长期向莱州湾扩散;丰水期黄河冲淡水几乎影响了整个莱州湾,27盐度锋可以到达莱州湾中部,27等盐线的表层包络面积为2 665.61 km²,占莱州湾的1/4左右,枯水期低盐度水只有向南扩散的趋势,27以下的低盐度水集中分布在黄河口门附近,27等盐线的表层包络面积只有199.65 km²;5月份,随着入海径流量增加,27等盐线扩散的范围、距离、方向都会发生明显变化。在对近海生物资源有迫切保护需求的情景下,适当减少其他用水户供水量以增加入海生态径流量,可以有效改善黄河口海域附近的盐度情况,为生物资源的生长繁殖创造良好条件。     

基于CART方法计算的黄河淡水水龄在渤海的分布变化特征

通过计算黄河淡水在渤海内部的水龄变化,能够进一步了解由黄河口排出的溶解性污染物在渤海中的输运时间和分布规律。利用ROMS(Regional Ocean Modeling System)数值模型,加入了基于CART(the constituent-oriented age and residence time theory)方法计算水龄的模块,用于计算黄河淡水水龄在渤海的分布以及长期变化规律。模式较好地再现了渤海物理场以及黄河淡水水龄在渤海中的分布。模拟结果显示水龄在空间分布上差异很大,莱州湾平均水龄为700天,而辽东湾则高达1760天。渤海中部与辽东湾水龄时空分布表现出季节变化,冬季辽东湾水龄西低东高,高龄水自辽东湾东侧入侵渤海中部;夏季辽东湾水龄西高东低,渤海中部低龄水占优。黄河淡水水龄在年际时间尺度上存在明显差异,1998—2003年黄河淡水水龄较高且存在上升趋势,而2003—2007年则迅速下降,此变化主要由黄河入海径流量的改变导致;径流量增大会使淡水水龄降低,反之则会使水龄升高。黄河径流量对黄河淡水水龄的影响主要是通过改变目标区域黄河淡水浓度和低龄淡水质点在水团中所占的比例来实现的。     

龙口近岸海域潮流作用下悬浮泥沙时空分布特征及输运机制

根据2015年1月与2017年5月两期大潮期27小时海流连续同步观测及悬浮泥沙资料,利用Morlet小波分析与单宽悬沙通量机制分解法,结合潮流场特征,分析了龙口湾海域悬浮泥沙的时空分布特征,研究了潮流作用下的悬沙输运机制。结果表明,平面上,悬沙浓度在龙口湾内较低,湾口、湾外海域的的悬沙浓度相对较高;垂向上,研究区整体表现为悬沙浓度由底层向表层递减。潮周期尺度上,悬浮泥沙浓度峰值较流速峰值存在0.5～2 h的时间滞后;悬浮泥沙浓度在时间上的变化以12～16 h尺度为主要周期。季节尺度上,1月悬沙浓度远远大于5月。研究区内单宽输沙通量为1.21～239.77 g·s-1·m-1,整体上悬沙通量呈现出湾口最高、湾外开阔海域其次、湾内最低的分布格局。平流输运项(T1+T2)在悬沙输移中占绝对优势,潮致余流在悬沙输运起主要作用。季节上,1月份单宽输沙通量远远高于5月份,整体呈现出夏季落淤储沙而冬季再悬浮输沙的季节性输运特征。湾外海域悬浮泥沙大致向SW、S向输运,屺坶岛以北海域沿W、SW向屺坶岛头输运,进入湾内后,悬浮泥沙的输运沿人工岛北侧和西侧分为两支。研究区内,在海流、地形等的综合作用下,整体表现为由渤海向莱州湾的净输沙趋势。     

Numerical simulation of sediment lifted by waves and transported by tidal currents

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High-resolution field measurements and numerical modelling of intra-wave sediment suspension on plane beds under shoaling waves

Intra-wave sediment suspension is examined using high-resolution field measurements and numerical hydrodynamic and sediment models within 120 mm of a plane seabed under natural asymmetric waves. The detailed measurements of suspended sediment concentration (at 5 mm vertical resolution and at 4 Hz) showed two or three entrainment bursts around peak flow under the wave crest and another at flow reversal during the decelerating phase. At flow reversal, the mixing length was found to be approximately double the value attained at peak flow under the crest. To examine the cause of multiple suspension peaks and increased diffusion at flow reversal, a numerical “side-view” hydrodynamic model was developed to reproduce near-bed wave-induced orbital currents. Predicted currents at the bed and above the wave boundary layer were oppositely directed around flow reversal and this effect became more pronounced with increasing wave asymmetry. When the predicted orbital currents and an enhanced eddy diffusivity during periods of oppositely directed flows were applied in a Lagrangian numerical sediment transport model, unprecedented and extremely close predictions of the measured instantaneous concentrations were obtained. The numerical models were simplified to incorporate only the essential parameters and, by simulating at short time scales, empirical time-averaged parameterisations were not required. Key factors in the sediment model were fall velocities of the full grain size distribution, diffusion, separation of entrainment from settlement, and non-constant, but vertically uniform, eddy diffusivity. Over the plane bed, sediment convection by wave orbital vertical currents was found to have no significant influence on the results.     

粤西水东湾现代沉积环境特征与泥沙搬运路径

对粤西水东湾沉积地貌单元的现代沉积物分布特征分析与泥沙净搬运矢量计算表明，滨面斜坡沉积物主要由砂粒级物质组成，粒级参数Ｍｄ，ＱＤ和ＳＫ具有从海向岸、自东向西变化的总趋势，泥沙净搬运趋势以向岸和西北为主。落潮三角洲沉积物较其邻近滨面斜坡有所粗化，分选从中部向两侧变好，泥沙在落潮流与波浪驱动下沿落潮三角洲边缘向西运动。口门内潮汐通道深槽泥沙净搬运趋势指向湖。湖区的沉积物以泥质为主，分选中等至差，并形成绕涨潮三角洲的泥沙环流元。     

近岸波浪和波生流环境中泥沙输运的数值模拟

Owing to lack of observational data and accurate definition,it is difficult to distinguish the Kuroshio intrusion water from the Pacific Ocean into the South China Sea(SCS).By using a passive tracer to identify the Kuroshio water based on an observation-validated three-dimensional numerical model MITgcm,the spatio-temporal variation of the Kuroshio intrusion water into the SCS has been investigated.Our result shows the Kuroshio intrusion is of distinct seasonal variation in both horizontal and vertical directions.In winter,the intruding Kuroshio water reaches the farthest,almost occupying the area from 18°N to 23°N and 114°E to 121°E,with a small branch flowing towards the Taiwan Strait.The intrusion region of the Kuroshio water decreases with depth gradually.However,in summer,the Kuroshio water is confined to the east of 118°E without any branch reaching the Taiwan Strait;meanwhile the intrusion region of the Kuroshio water increases from the surface to the depth about 205 m,then it decreases with depth.The estimated annual mean of Kuroshio Intrusion Transport(KIT) via the Luzon Strait is westward to the SCS in an amount of –3.86×106 m3/s,which is larger than the annual mean of Luzon Strait Transport(LST) of –3.15×106 m3/s.The KIT above 250 m accounts for 60%–80% of the LST throughout the entire water column.By analyzing interannual variation of the Kuroshio intrusion from the year 2003 to 2012,we find that the Kuroshio branch flowing into the Taiwan Strait is the weaker in winter of La Ni?a years than those in El Ni?o and normal years,which may be attributed to the wind stress curl off the southeast China then.Furthermore,the KIT correlates the Ni?o 3.4 index from 2003 to 2012 with a correlation coefficient of 0.41,which is lower than that of the LST with the Ni?o 3.4 index,i.e.,0.78.     

Combined numerical model of currents, waves, and sediment transport in Lake Donuzlav

We present a numerical model of the dynamics of Lake Donuzlav, which enables one to perform simultaneous numerical analyses of the currents, sea level, waves, and sediment transport. The model is based on the hydrodynamic block and the spectral wave model. For typical storm situations, we study the specific features of the integral circulation of waters and the three-dimensional structure of currents, investigate the wind-induced wave fields, and evaluate the flows of sediments and deformations of the bottom. The presence of intense eddy structures is revealed in the field of currents caused by the bottom topography. A significant intensification of waves in the south part of the lake is established in the case of penetration of storm waves through the strait. It is shown that the account of waves leads to qualitative changes in the structure of circulation in the lake and to the formation of well-pronounced areas of wave-induced elevations and lowerings of the sea level. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 43–65, March–April, 2006.     

Deposition of coarse-grained sediments in the Korea Strait during late Pleistocene low sea level

The wide area of the Korea Strait shelf is covered by a thin veneer of gravelly sands, sands, or muddy sands. Most gravels are sub- to well-rounded and their content reaches up to 25%. These sediments were derived from the Korean Peninsula through the paleochannel of the Nakdong River, which extended onto the mid-shelf during late Pleistocene low sea level. The gravel distribution pattern suggests reworking and transport of the sediments by strong currents during times of low sea level.     

古长江河口湾充填潮流作用机制的初步探讨

长江三角洲的发育是以古长江河日湾的充填来实现的.研究潮汐、潮流在古长江河口湾充填中所起的作用,可深入了解长江三角洲的形成发育过程.建立了渤海、黄海、东海的二维潮流数学模型,数值模拟了冰后期最大海侵,即现今长江三角洲地区为巨大河口湾时的M2潮汐、潮流.在此基础上,计算了古长江河口湾及其周围海域8种粒径泥沙的潮平均悬移与推移输沙率,并根据输沙率散度的正负,划分了海底冲刷区与淤积区.根据计算结果得出,冰后期最大海侵时,存在大致以古长江河口湾湾口中点为腹点、波腹线向海凸起的独特驻潮波波腹区.在其控制下,外海潮流大致以古长江河口湾湾口中点为顶点作辐聚、辐散运动.在古潮流场作用下,经历每一个潮周期后,古长江河口湾周围海域的泥沙均向河口湾内净输运,并在河口湾内淤积.古长江河口湾的充填是在长江带来大量泥沙,外海的潮汐、潮流又有利于泥沙向河口湾内净输运,且在河口湾内沉积的情况下实现的.外海的潮汐、潮流为古长江河口湾的充填、长江三角洲的发育提供了必要而又有利的水动力环境.     

A sheetflow sediment transport model for skewed-asymmetric waves combined with strong opposite currents

Prototype scale physical model tests were conducted to investigate the sheetflow sediment transport of uniform sand under different skewed-asymmetric oscillatory flows with and without the presence of relatively strong currents in the opposite direction against wave propagation. Experiments show that in most cases with fine sands, the “cancelling effect” which balances the on-/off-shore net transport under pure asymmetric/skewed oscillatory flows and results a moderate net transport was developed for combined skewed-asymmetric shaped oscillations. However, under certain conditions (T > 5 s) with coarse sands, the onshore sediment transport was enhanced for combined skewed-asymmetric flows. Additionally, the new experimental data under collinear oscillatory flows and strong currents show that offshore net transport rates increase with decreasing velocity skewness and acceleration skewness. Sediment movement behaviors were investigated through analysis of experimental data obtained from the image analysis technique and attempts were made to estimate and formulate the sheetflow layer thickness. Accordingly, sediment transport under oscillatory sheetflow conditions was studied and successfully explained by comparing the bed shear stress and the phase lag parameter at each half cycle. Consequently, these parameters were incorporated in an improved Dibajinia and Watanabe's type sediment transport model. The formula is calibrated against a comprehensive experimental data (331 in total). Good agreement obtained between predictions and measurements shows that the new formula is fulfilled for practical purposes.     

渤海的环流、潮余流及其对沉积物分布的影响

阐明渤海环流和潮余流的分布特征及其与沉积物输运之间的关系。本文根据８０年代以来的实测海流资料得到：辽东湾的环流是顺时针向的；黄河三角洲外海存在着一支流向东北偏北向流，与辽东湾西部的东北向海流相接；渤海湾内的环流北部为反时针向，南部为顺时针向回转的双环结构。上述环流趋势与渤海沉积物分布相一致。渤海沿岸主要入海河流的特征矿物分布正在上述环流存在的最好佐证。文中进一步讨论了潮余流分布特征及其对渤海环流的     

Effect of Development of Caofeidian Harbor Area in Bohai Bay on Hydrodynamic Sediment Environment

Based on the characteristics of waves, tidal currents, sediment and seabed evolution in the Caofeidian sea area in the Bohai Bay, a 2D sediment mathematical model of waves and tidal currents is employed to study the development schemes of the harbor. Verification of spring and neap tidal currents and sediment in the winter and summer of 2006 shows that the calculated values of tidal stages as well as flow velocities, flow directions and sediment concentration of 15 synchronous vertical lines are in good agreement with the measured data. Also, deposition and erosion of the sea area in front of Caofeidian ore terminal induced by suspended load under tidal currents and waves are verified; it shows that the calculated values of depth of deposition and erosion as well as their distribution are close to the measured data. Furthermore, effects of reclamation scheme of island in front of the land behind Caofeidian harbor on the hydrodynamic environment are studied, including changes of flow velocities in the deep channels at the south side of Caofeidian foreland and Laolonggou and in various harbor basins, as well as changes of deposition and erosion of seabed induced by the project.