FVCOM模型关键参数的处理及其在涌潮模拟中的应用

通过改进海床阻力系数和设置合适的垂向紊动背景系数,应用FVCOM模型成功再现了钱塘江河口强涌潮的演进过程。海床阻力系数采用Manning公式形式,取值随水深、地形在0.000 2~0.002 9之间变化;垂向紊动背景系数取1×10^-4 m²/s。模拟结果较好地复演了涌潮到达时刻、涌潮高度及涌潮抬升过程、涌潮水平流速以及其沿垂向分布规律,表明阻力系数及垂向紊动背景系数等关键参数的改进和处理是合理的,可应用于涌潮三维潮流运动特征模拟。     

青岛海湾大桥对胶州湾潮汐、潮流及余流的影响预测——Ⅲ.预测方法及预测结果

在潮流数值模型中,采取了如下办法表示桥墩:桥墩造成的截水面积通过减小水深来实现,桥墩的阻尼通过增加底摩擦实现。根据以上水深处理和水力学实验给出的阻尼系数,在胶州湾及邻近海域计算潮流场基础上,预测了青岛海湾大桥对胶州湾潮汐、潮流及余流的影响。     

围垦工程引起多年海岸冲淤演变的经验计算方法

提出了一个改进的经验公式,用以计算围垦工程引起的淤泥质海岸多年冲淤演变。该经验公式假定在年时间尺度上,地形变化与潮流场变化具有密切联系。引入了一个冲刷折减系数,将传统公式的适用范围从淤积计算拓展到可以同时计算冲刷和淤积。建立了冲淤率年际变化与水深变化之间的关系式,可节省计算时间。将改进公式应用于江苏沿海小庙洪水道,较好地复演了边滩围垦工程影响下周边地形在3年时间内的演变,表明所改进的公式具有一定的可靠性。     

Crucial physical characteristics of sea ice in the Arctic section of 143°-180°W during August and early September 2008

潮流是水下地形SAR成像的决定性因素之一,潮流的周期性变化使水下地形SAR成像与潮流场有密切的关系,同一水下地形不同时刻SAR影像不同。以台湾浅滩为例,基于5景不同时相的ERS-2 SAR影像和台湾浅滩实测水深数据,开展了水下地形SAR成像与潮流场的相关性分析。为了排除SAR影像自身成像质量对研究的影响,首先对5景SAR影像的成像质量进行评价,然后通过潮汐潮流数值计算确定SAR成像时刻的潮流场以及基于QuikScat散射计数据确定SAR成像时刻的海面风向。在上述基础上开展了SAR影像后向散射系数与实测水深的相关性分析,总结出水下地形SAR成像与潮流场的关系,结果表明,潮流场与水下地形SAR成像密切相关,当潮流流向与水下地形梯度方向一致或接近时,水下地形SAR成像效果最佳;对于同一水下地形,流向相反的两种潮流对应的SAR影像后向散射系数恰好相反,即SAR影像中的明暗条纹不同。相对于潮流流向的顺流与逆流风向的不同对水下地形SAR成像无影响。     

水下地形SAR成像与潮流场的相关性分析示例

潮流是水下地形SAR成像的决定性因素之一,潮流的周期性变化使水下地形SAR成像与潮流场有密切的关系,同一水下地形不同时刻SAR影像不同。以台湾浅滩为例,基于5景不同时相的ERS-2 SAR影像和台湾浅滩实测水深数据,开展了水下地形SAR成像与潮流场的相关性分析。为了排除SAR影像自身成像质量对研究的影响,首先对5景SAR影像的成像质量进行评价,然后通过潮汐潮流数值计算确定SAR成像时刻的潮流场以及基于QuikScat散射计数据确定SAR成像时刻的海面风向。在上述基础上开展了SAR影像后向散射系数与实测水深的相关性分析,总结出水下地形SAR成像与潮流场的关系,结果表明,潮流场与水下地形SAR成像密切相关,当潮流流向与水下地形梯度方向一致或接近时,水下地形SAR成像效果最佳;对于同一水下地形,流向相反的两种潮流对应的SAR影像后向散射系数恰好相反,即SAR影像中的明暗条纹不同。相对于潮流流向的顺流与逆流风向的不同对水下地形SAR成像无影响。     

黄、东海环流的数值研究Ⅱ潮及潮致环流数值模拟

该文中数值模拟了黄、东海陆架区的四大天文潮及其潮致拉格朗日环流。运用“流速分解法”将线性三维分潮波问题化为一个分潮潮位及深度平均流的二维问题和一个流速垂向剖面问题求解。其二维问题的底摩擦系数由三维模式导出 ,所导得的线性底摩擦力公式更符合物理意义 ,且避免一般二维模式中底摩擦力的经验假定。结果表明 ,三维模式完全可以通过准二维方法求解 ,以避免一般三维问题的繁重计算     

One-Dimensional Unsteady Analytical Solution of Salinity Intrusion in Estuaries

Based on the one-dimensional salinity transport equation with constant diffusion coefficient, and separated water flow velocity into runoff and tidal current with the single-frequency in an idealized estuary, the simplest unsteady analytical so- lution of salinity intrusion is deduced and the estimation formula of diffusion coefficient is obtained in this paper. The unsteady solution indicates that salinity process in estuaries results from the interaction of runoff and tidal current, and its amplitude is in direct proportion to the product of the velocity of runoff water and the amplitude of tidal flow velocity and in inverse proportion to the diffusion coefficient and the tidal angular frequency, and its phase lag tidal flow with 7/2 which reveals the basic features of the maximum salinity appearing after flood slack and the minimum salinity appearing before ebb slack under the effect of runoff （the advance or lag time is relative to the magnitude of runoff and tidal flow）. According to the measured flow velocity and salinity data, the salinity diffusion coefficient could be estimated. Finally, with the field data of observing sites on the deepwater navigation channel of the Yangtze Estuary, the diffusion coefficient is calculated and a comparative analysis of simulated and measured of salinity process is made. The results show that the solution can comprehensively reflects the basic characteristics and processes of salinity intrusion under the interaction of runoff and tidal flow in estuaries. The solution is not only suitable for theoretical research, but also convenient for estimating reasonable physical parameters and giving the initial condition in the salinity intrusion numerical simulation.     

崇明岛南侧盐沼潮滩消能状态研究

沿海盐沼潮滩可以有效降低波浪高度,耗散波浪能量,在海岸防护和沿海城市安全中扮演着重要角色。以长江河口崇明岛南侧盐沼潮滩为对象,基于不同潮间带实测波浪变化数据,采用波能衰减模型对波浪横向沿潮滩衰减状态进行定量分析,由此探讨波浪衰减主控要素。结果表明:波浪沿盐沼潮滩向岸传播过程中,波高以及波能大幅下降,其中光滩—芦苇前部区域波能平均下降19%,芦苇区域波能平均下降71%,有植被覆盖区域对波浪的衰减效应更为显著。同时,水深、入射波高及阻力是影响盐沼潮滩波浪衰减的主要因素,波浪衰减强度随水深增大而减小,入射波高增加以及阻力的增大而增强。     

Quantification of dune dynamics during a tidal cycle in an inlet channel of the Danish Wadden Sea

High-resolution swath bathymetry measurements at centimetre-scale precision conducted during a tidal cycle in the Grådyb tidal inlet channel in the Danish Wadden Sea reveal the short-term dynamics of a large, ebb-directed compound dune with superimposed small to medium dunes, all composed of medium sand. Dune dynamics were related to simultaneous measurements of flow using an acoustic Doppler current profiler. Spatially, dune crests displayed greater mobility than did dune troughs, due to higher flow velocities at the crests than in the troughs. Temporally, superimposed lower lee-side dunes migrated more during the flood than the ebb tide, due to higher near-bed trough flow velocities during the flood phase, resulting in varying exposure to flow. Net dune migration was flood-directed over the tidal cycle, despite annual net migration being ebb-directed. Hence, extrapolation of short-term migration rates is not possible in this case. The superimposed dunes reversed direction during each half tidal cycle whereas the compound dune only developed a flood cap during flood tide, i.e. the time required for complete reversal of the compound dune was much longer than that available in a half tidal cycle. Over the tidal cycle, the bed level was stable but significant erosion and accretion occurred during the tidal phases. During the ebb tide, bed material was brought into suspension with accelerating flow and settled with decelerating flow, resulting in an average erosion and accretion of the bed of ~7 cm in each case. During the flood tide, the bed of the compound dune was overall stable, although bed material was eroded from the exposed lower lee side, being partly transported to the crest in bedload and partly brought into suspension. In general, dune height fluctuated during the tidal cycle whereas dune length remained stable. The height of the compound dune responded to changes in water depth, which acts as a limiting factor to dune growth. By contrast, the height of the stoss-side dunes responded to flow velocity, i.e. the stoss-side dunes were water depth-independent.     

海洋倾倒区容量评估模型的构建

倾倒区容量主要受海水动力过程(潮流输沙、风暴潮和风浪掀沙等)、倾倒区面积和水深地形等因素影响。本文基于FVCOM(Finite Volume Coast and Ocean Model)三维数值模型和随机动态统计分析模型, 利用倾倒区地形演变和倾倒量资料, 探讨海水动力过程(潮流输沙、风暴潮和风浪掀沙等)和倾废活动对海底地形变化的影响, 构建海洋倾倒区容量长期演变评估模型。利用FVCOM水动力和泥沙模型计算自然状态下潮流输沙引起的地形变化, 同时结合倾倒区多年实测水深和倾倒量资料, 分析倾倒量、潮流输沙和地形变化的统计关系, 通过实际资料拟合修订系数, 作为该倾倒区海浪和风暴潮等因素输沙所造成地形变化的参考值, 以此评估倾倒区容量长期演变。在设定实际地形变化阈值的前提下, 计算倾倒区容量。以长江口1#倾倒区为例, 1#倾倒区地形抬升0.5m/a,倾倒区容量约为670万方/a,模型结果和实际批复结果吻合。同时在甬江口2#倾倒区、罗源湾倾倒区、嵊泗上川山、东碇倾倒区和温州港倾倒区等验证, 模拟结果同实际观测结果相近。     

苏北近岸海域表层沉积物粒度及其对环境动力的响应

对2007年9—11月在南黄海辐射沙脊区和江苏北部潮滩采集的表层底质样品进行粒度分析,获得了平均粒径、分选系数、偏态、峰态等粒度参数,并对其进行了聚类分析。结果表明,9 m以浅和20 m以深的样品可归为两种类型的沉积物,而水深9～20 m之间的沉积物两种类型都有,多样性较大。由Gao-Collins粒径趋势分析模型获得的沉积物净输运趋势显示,除外毛竹砂处沉积物有向外海输运的趋势之外,其他外围的断面均显示泥砂向辐射沙洲中心输运,这与历史资料中记录的结果相一致,表明粒径趋势分析适用于大型辐射沙洲海域。根据Stern-berg图分析,粒度参数的空间分布是由差异性输运造成,沉积物从射阳河口岸外向大丰潮间带上部输运的过程中,众数粒径几乎全部以悬移质的形式输运,而小庙洪向东灶潮滩上部输运的众数粒径以悬移方式输运的概率只有60%,从而使射阳河口岸外与大丰潮间带上部的沉积物粒度参数相同,而小庙洪与东灶潮间带上部的沉积物粒度参数有显著差异。     

三门湾外海的潮汐和潮流特征

针对2009年5月-7月三门湾外海D8和D9两个站位布放的防渔网底拖锚系ADCP连续观测获取的流速资料和水位资料,采用调和分析和功率谱分析等研究方法,分析了该海域的潮汐和潮流特征,结果显示:该海域潮汐类型为正规半日潮,近岸的D9站浅水分潮比离岸的D8站显著,潮汐呈现出回归潮特征。三门湾外海潮流半日分潮能量最大, 各层潮流呈现出旋转流性质;椭圆率随水深增加;M₂、K₁分潮流最大流速均在次表层最大;最大分潮流速发生时刻底层比中、上层提前约半小时;该海域潮流的半日分潮流以正压为主,全日分潮流则表现出较为明显的斜压性。     

珠江河口盐度和输运过程对未来海平面上升的响应

研究海平面上升对河口的影响情况有助于了解输运过程的变化,基于21世纪海平面上升预测研究(陈长霖,2012;张吉,2014),本文选取珠江河口这一径优型与潮优型并存的河口为研究区域,利用数值模拟的方法,研究其在未来海平面上升后可能出现的响应。结果表明,河口的平均盐度、咸潮上溯距离和层化强度都将随着海平面的上升而增加,这些因素的变化有着明显的季节性。伶仃洋平均盐度在4月和10月增加更多;伶仃洋枯水期咸潮上溯距离的增量大于丰水期,磨刀门则相反;伶仃洋丰水期层化强度及其增量都要大于枯水期。海平面上升后的输运过程响应结果显示:(1) 垂向输运时间将增加,虽然海平面上升带来的潮差潮流的增强将加强垂向混合,但是层化的加强会削弱垂向交换。垂向输运时间的增加是由于层化的加强,层化加强抑制了潮汐变化带来的影响,表层水更难交换到底层; (2) 南北向河口环流将加强,表层余流向海加强,底层余流向陆加强,南北向余流整体向海减小。造成这些现象的主要原因是海平面上升后水深增加带来的河道比降的减小和压力梯度力的改变。     

九龙江河口湾泥沙运移特点与沉积动力机制

本文研究了九龙江河口湾的泥沙动物特点与沉积动力机制。结果表明：（１）泥沙主要来地河流输沙和潮流输沙;潮流输沙星明显大于河流输沙星;涨潮输沙星通常大于落潮输沙量;潮流输沙在枯水期尤为显著,而河流输沙则集中在洪水期。（２）底沙推移运动主要发生在水道床面,系局部冲刷所致;推移质输沙表现为沙洲推移,沙嘴延伸或水下沙体游移,研究发现,在涨潮流占优势的鸡屿北水道有反向,推移质输输沙的迹象。（３）自６０年代以来     

悬浮体粒度特征所反映的南黄海辐射沙脊群泥沙扩散趋势

基于大量的悬浮体现场粒度和浓度数据,借助细颗粒悬浮体作为示踪物,分析了潮流作用下南黄海辐射沙脊群海底沉积物的再悬浮和扩散特征,并探讨了沙辐射沙脊群以北泥质区的形成机制。研究结果表明：（1）在辐射沙脊群以北,近岸悬沙在离岸方向上的扩散受到限制,向南又被辐射沙脊群中心浅滩所阻挡,只能在辐射沙脊群与废黄河口之间形成沿岸分布的高浓度浑水团。（2）辐射沙脊群以北的往复潮流对海底沉积物有分选作用,倾向于把海底沉积物中的粗颗粒分选搬运至沙脊群,把细颗粒沉积物向北输送,从而在沙脊群以北形成泥质区。（3）在正常海况下,沙脊表层沉积物再悬浮作用十分微弱,沙脊上覆水体中的悬沙主要来自于临近沟槽海底沉积物的水平扩散。     

潮流能发电装置支撑结构对水轮机水动力学性能影响研究

水平轴潮流能水轮机在工作过程中,由于支撑结构的存在,会使水轮机周围流场中的潮流流向、流速等参数发生不同程度的改变,进而影响水轮机的性能和发电装置的稳定性。为了研究支撑结构对水轮机水动力学性能的影响规律,以某100 k W单立柱座底式潮流能发电装置的支撑结构为研究对象,采用CFD方法,分别在正、反向来流时采用不同支撑结构的共六种工况下,对潮流能水轮机模型的获能和受力进行数值模拟。通过水槽模型试验,验证数值模拟的可靠性。研究结果表明:支撑结构对水轮机的水动力学性能的影响不容忽视,针对所研究的支撑结构,在正向来流时水轮机的获能系数降幅约30%,轴向力系数降幅约28%;反向来流时的降幅更大,分别约为63%和41%。     

长江河口拦门沙河床淤积和泥沙再悬浮过程

利用近２０年来长江河口所观测的地形、水文、悬沙和河床沉积物资料,着重对１９８８、１９８９、１９９６和１９９７年最新观测资料进行计算分析。结果表明,长江河口航道拦门沙河段来水沙量大,潮流作用强,潮波变形明显,水流挟沙力强。该河段潮流速随时间和空间变化,又处在盐淡水交换地带,流域和海域来沙在此河率时淤时冲,悬沙与床沙交换频繁,表现在涨急、落急时可床淤积层泥沙再次起动悬浮,憩流时只河床,在一个潮周期中含     

广利河口航道整治研究

广利河口拦门沙航道水深较浅,用双导堤结合航道疏浚进行整治。通过潮流定床模型试验对航道走向、导堤间距、高程、水流流态和堤头布置等进行了方案优化,同时采用局部动床定性试验进行了验证。推荐方案沿程流速、流态分布合理,基本能维持航道水深并满足设计船型的航行条件,可供类似河口治理参考。     

Bed load transport on the shoreface by currents and waves

Tide-driven bed load transport is an important portion of the net annual sediment transport rate in many shoreface and shelf environments. However, bed load transport under waves cannot be measured in the field and bed load transport by currents without waves is barely measurable, even in spring tidal conditions. There is, consequently, a strong lack of field data and validated models. The present field site was on the shoreface and inner shelf at 2 to 8.5 km offshore the central Dutch coast (far outside the surfzone), where tidal currents flow parallel to the coast. Bed load transports were carefully measured with a calibrated sampler in spring tidal conditions without waves at a water depth of 13–18 m with fine and medium sands. The near-bed flow was measured over nearly a year and used for integration to annual transport rates. An empirical bed load model was derived, which predicts bed load transports that are a factor of > 5 smaller than predicted by existing models. However, they agree with laboratory data of sand and gravel transport in currents near incipient motion. The damped transport rates may have been caused by cohesion of sediment or turbulence damping due to mud or biological activity. The annual bed load transport rate was calculated using a probability density function (pdf) derived from the near-bed current and orbital velocity data which represented the current and wave climate well when compared to 30 years of data from a nearby wave station. The effect of wave stirring was included in the transport calculations. The net bed load transport rate is a few m²/year. This is much less than predicted in an earlier model study, which is partly due to different bed load models but also due to the difference in velocity pdf. The annual transport rate is very sensitive to the probability of the largest current velocities.     

台湾浅滩大型沙波、潮流结构和推移质输运特征

对2006年8月所获台湾浅滩的底质、水深、多层位流速、流向以及CTD观测数据进行了分析,探讨了台湾浅滩大型沙波区水流的时空分布特征、沉积物输运过程及影响因素,结果表明,台湾浅滩动力作用较强,底质为粗砂,其上发育的沙波波长为325~822 m,波高为14.4~20.3 m,较接近由前人总结的沙波波高、波长的关系式计算出的波高和波长。沙波波峰、波谷、迎水面和背水面流速以12.5 h为周期沿顺时针方向旋转;底部最大流速出现在半日潮周期的同一时段,对应的方向均为偏南方向,且沙波迎水面的流速大于背水面的。在两个半日潮过程中研究区域的沉积物输入量大于输出量,处于淤积状态。在潮流作用下沉积物输运量较少,沙波脊线移动较小,而台湾浅滩有较大规模的沙波运动,故认为改造沙波的主要作用力应该是风暴流。在观测的断面中涨潮推移质输运量大于落潮的,且第一个半日潮涨落潮的输运能力均较第二个半日潮的大,这可能与潮流的流速-时间不对称特征及潮能变化形式有关。