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珠江磨刀门河口径潮动力耦合条件下余水位的多时空尺度分析 总被引：3，自引：3，他引：0
本文通过构建径潮动力耦合条件下潮波传播的一维水动力解析模型，从理论机制上探讨珠江磨刀门河口径潮动力非线性作用下余水位的多时空尺度变化。结果表明:余水位变化呈现明显的大小潮和洪枯季变化，枯季余水位大小潮的变化幅度介于0~0.4 m，而洪季余水位与上游径流紧密相关，增幅大枯季一个量级（介于0~6 m）；解析模型可分离控制余水位变化的3个主要因素，即径流、潮流和径潮相互作用因子，计算结果表明河口不同区段余水位的主控因素有明显的洪枯季变化，上游段，枯季余水位受径潮相互作用因子控制，洪季受径流因子控制；枯季下游段余水位受潮流控制，而洪季余水位主要受径潮相互作用因子控制。 相似文献
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河口环流结构关系到物质输运、泥沙沉积和地貌变化等物理过程。根据2019年磨刀门河口原型观测平台洪枯季连续观测分层潮流资料,统计洪枯季、大小潮河口东、西汊的涨落潮流及历时变化特征,利用理论方法解析河口东西汊平面环流和重力环流结构,进一步引入混合参数研究河口纵向环流中的潮汐应变环流。研究发现枯季东、西汊在转潮时刻存在东涨西落的平面环流结构,洪季平面环流特征较不明显;枯季重力环流强度整体略大于洪季,西汊重力环流强于东汊,表层向海环流流速可达0.2～0.25 m/s,而底层向陆环流流速相对较小。洪季大潮期由潮不对称性驱动的潮汐应变环流相对较大,进而增强了纵向环流的强度。河口垂向余流结构同样表现洪枯季、大小潮的变化规律。洪季余流整体较大,西汊在小潮期表层余流流速超过0.6 m/s,而东汊余流则明显呈现表层向海、底层向陆的分布特征,枯季余流整体较小,表明其对物质输运和河口地形塑造作用较弱。 相似文献
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河控型河口盐度混合和层化是控制悬沙输移扩散的重要动力机制。以珠江磨刀门河口为研究对象,基于2017年洪季三船同步大、小潮水文泥沙观测数据,分析河控型河口水体盐度层化结构的时空变化对悬沙分布的影响机制。结果表明:受径潮动力耦合时空变化影响,河口盐度垂向分布表现出时空差异,即受径流主导的M1站(挂锭角),河口盐度在涨落潮周期内垂向混合均匀,受径潮控制的M2站(口门)在整个潮周期内盐度层化结构明显,口门外侧的M3站,潮动力作用较强,盐度垂向分布随涨落潮变化而变化;悬沙空间分布与盐度分布关系密切,盐度混合均匀利于悬沙垂向均匀分布,而盐度层化则使悬沙倾向于滞留在底层水体中,且在盐度层结界面之下出现高悬沙浓度,悬沙浓度垂向分布曲线呈L字型或抛线型,纵向上表现为高浓度悬沙团抑制在盐水楔前端,盐度层化对悬沙的捕集效应明显。通过对比水体标准化分层系数与水流垂向扩散强度系数发现,两者呈现负相关关系,即标准化分层系数愈大,垂向扩散强度愈小,表明水体层化抑制悬沙垂向扩散强度,而且水体层化程度越高,悬沙垂向扩散抑制程度越大,进而促进了河口水体盐度层化对悬沙捕集作用。本研究有助于揭示河口细颗粒泥沙运动机制及河口拦门沙演变机制,并为磨刀门河口拦门沙治理提供科学依据。 相似文献
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基于伶仃洋河口2007年洪季（8月）潮流和泥沙现场观测资料,通过实测资料分析结合二维泥沙数值模型的方法,分析其悬沙浓度平面分布特征。结果表明,悬沙浓度从伶仃洋湾顶虎门至湾口沿西槽向海在纵向上呈现出先减小再增大后减小的变化趋势;横向上,西槽最大,东槽和中滩次之;内伶仃岛西北侧海域为含沙量高值中心。悬沙纵向输移机制分析表明,伶仃洋洪季输沙主要贡献项为平流向海输沙、潮汐捕集和垂向环流的向陆输沙,其中后两项在内伶仃岛附近的贡献较大。潮流、径流来沙、径潮强度对比以及地形边界作用为悬沙场平面分布差异的主要成因。 相似文献
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长江分汊河口涨、落潮悬沙不对称特征及季节性差异 总被引：1，自引：1，他引：0
入海河口由于径流的存在以及河口地貌形态的影响，存在涨、落潮水动力、悬沙以及盐度分布等不对称现象，同时这一不对称现象还存在显著的区域性和季节性差异。根据2013年7月和2014年1月洪、枯季长江口定点准同步水文泥沙调查结果，发现长江口分汊型河槽悬沙浓度在时间上存在洪枯季、大小潮不对称特征，在空间上存在东西向沿程分布、南北向横向分布以及垂向上表底层分布不对称特征。河势演变形成南、北支河口涨、落潮悬沙浓度不对称分布的整体格局；洪、枯季变化影响河口涨、落潮悬沙分布的再分配过程；大潮涨、落潮过程对悬沙分布不对称影响显著大于小潮；季节性风浪作用影响河口最大浑浊带涨、落潮悬沙不对称南北差异；底部高含沙浓度对口门段涨、落潮悬沙不对称性贡献显著。 相似文献
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河口水流是河口生态环境、河道演变、物质输运等物理过程的根本动力。由于径流、潮波、地形以及气象等因素的影响,河口水流呈现复杂的三维结构。其中既包括淡水注入形成的余流,也包括周期性的潮流、风生流、斜压流及河口非线性作用导致的流动等。为探究河口水流的组成及其潮内变化,基于瓯江口实测资料,利用主成分分析（Principal Component Analysis, PCA）法对河口水流进行分解,探讨了PCA法对河口水流的分解性能及斜压分潮流的高频特征。研究认为,PCA法在河口水流结构研究中既可采用原始数据操作亦可用标准化的数据进行计算。PCA法可分解出斜压成分（河口重力环流型结构）,但不能将正压成分（径流和潮流）分开,径流和潮流二者综合作用的结果体现在主成分的得分之中。主成分的取舍应根据水流结构和累计解释方差综合判断,不宜仅依据累计解释方差。河口斜压流动具有明显的高频特征,近似呈1/4日分潮的周期。 相似文献
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珠江河口伶仃洋水域潮波传播变形及其不对称性关系对河口动力环境和物质输运产生影响。研究根据珠江口伶仃洋及东四口门19个潮位站2011年6月实测逐时潮位, 利用收缩河型沿程潮幅解析理论, 阐释伶仃洋从桂山岛上行沿程潮汐传播规律特征; 在调和分析基础上, 应用偏度理论和分潮组合分析方法, 阐明了伶仃洋东西岸及洪奇门、蕉门内潮汐不对称性分布特征, 对照数值研究结果, 指出伶仃洋至虎门之间水域导致潮汐不对称性的主控因素及响应规律。研究表明, 河口平面形态呈近似指数收缩特征的伶仃洋, 沿程潮幅的变化符合指数收缩型河口波幅解析变化规律, 东岸潮幅高于西岸的主要原因是东岸水深大于西岸, 其次是科氏力影响; 行进潮波虽受地形摩擦耗能及非线性作用下不同频率分潮间能量迁移的影响, 但收缩河口能量汇聚效应可以保证收缩段天文分潮潮幅减缓衰减甚至增加, 半日分潮能量汇聚效果强于全日分潮, 各非线性项作用促使浅水分潮产生并持续增能, 保证一定距离内沿程潮幅的增大; 潮汐不对称性的偏度由湾口落潮占优向湾顶涨潮占优发展, 在伶仃洋中部赤湾至金星港一线转为涨潮占优, 产生该现象的原因是自湾口向湾顶不同频率间天文分潮K1-O1-M2的相互作用, 导致表现为落潮优势潮的不对称性减弱, 而天文分潮M2和其对应的浅水分潮倍潮M4组合作用使涨潮优势偏度值的不对称性增强; 收缩河口形态属性要素中, 水深是影响潮不对称性的最主要因素。 相似文献
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珠江河口磨刀门水道枯季盐水入侵特性分析 总被引：1，自引：0，他引：1
为探讨磨刀门水道潮流和盐度的三维分布特性,本文建立了磨刀门水道的三维潮流和盐度数值模型,采用2009年枯季磨刀门水道实测潮流和盐度资料对模型参数进行率定和验证。结果显示,枯季由于上游径流量小,磨刀门水道总体涨、落潮流速都不大,表层总体涨潮平均流速都在0.5 m/s以内,总体落潮平均流速在0.8 m/s以内;底层总体涨落潮平均流速都在0.5 m/s以内;从盐度的平面分布来看,磨刀门水道近口门河段总体呈现涨潮时水道东侧盐度高于西侧,落潮时东侧盐度小于西侧的趋势。大潮和中潮期间,落潮时盐水向上游的入侵距离反而较涨潮时更远,主要原因是,落潮时的底层盐水向上游的补偿流动以及地形阻拦形成更为强烈的紊动扩散。潮汐动力弱(小潮)时,整个水道内水流流速很小,流态平缓,紊动较弱,总体仍呈现涨潮时入侵距离大于落潮,显示枯季磨刀门水道盐水入侵的主要影响因素取决于地形和潮动力。 相似文献
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长江河口盐水入侵对大通枯季径流量变化的响应时间 总被引：4，自引：3，他引：1
应用河口海岸三维数值模式, 计算区域包括大通至长江河口及其邻近海域, 设计高分辨率网格, 数值模拟和分析不同潮型下长江河口盐水入侵对大通径流量变化的响应时间。计算结果表明, 不同潮型期间大通径流量的增加, 河口盐度响应的时间在4.0～6.2 d之间, 但小潮期的响应时间明显长于其他潮型期的响应时间。本文给出了长江河口盐水入侵对大通枯季径流量变化的响应时间, 可为河口水文、泥沙和环境等研究中取何时径流量提供了依据。 相似文献
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近20 a来，受高强度人类活动影响，珠江伶仃洋滩槽已发生远超自然过程的异变，其河口动力结构必然发生响应，影响物质输运过程。本研究利用三维水动力数值模型，探讨了伶仃洋河口小潮期余环流结构的变化特征及原因。结果表明：近20 a来伶仃洋底层余流强度提高，沿深槽上溯时向中滩偏转，易引起泥沙汇聚于此。中滩存在表层向西，底层向东的横向余环流结构，主要由非线性对流项和科氏力项驱动。中滩大规模采砂后引起对流项变化，造成余环流结构东移，表、底层余流增强，可加快表底层物质交换。西槽内存在表层向海、底层向陆的纵向余环流结构，主要由正压和斜压梯度力驱动。受浚深影响，向陆斜压梯度力和非线性对流项均增强，引起表层余流减小22%，而底层增大24%，这将削弱小潮期西槽内水体交换能力，即减慢物质输出，易造成西槽淤积、水环境恶化等影响。研究成果对研究人类活动干扰下的河口余环流结构及物质输运响应具有一定借鉴意义。 相似文献
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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
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基于珠江河口水文实测资料和三维水动力数值模型,利用有限时间李雅普诺夫指数提取分析了流场中的拉格朗日拟序结构(LCSs),并结合卫星遥感图像探讨珠江河口LCSs时空分布与其浊度锋的关系。结果显示,河口浊度锋与LCSs在时空上存在很好的契合,LCSs所形成的输运通道与壁垒对河口浊度锋的位置、形态及变化过程有显著影响。落潮时,泥沙随蕉门、洪奇门和横门的落潮射流注入伶仃洋,与虎门下泄的冲淡水对峙形成了一条明显的FTLE脊线,制约着浊度锋的形成和分布形态。涨潮时,来自西北三口门的淡水径流受口门外涨潮流的顶托作用,强烈的水平速度与密度梯度在此处形成LCS,阻碍径流挟带悬浮泥沙的输运而产生浊度锋。由于LCSs很好地勾画了不同动力性质的水体边界,因此可以用来对河口浊度锋进行识别、追踪和动力解释。 相似文献
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珠江伶仃河口湾及邻近内陆架的纵向环流与物质输运分析 总被引：1，自引：0，他引：1
根据实测资料分析了珠江伶仃河口湾与邻近内陆架在不同径流影响下的水体混合空间状态和季节变化特征。主要由河口湾表、中层冲淡水和内陆架底层上溯的高盐补偿流构成了河口湾和内陆架之间的净环流,在高径流量和西南大风的情况下,环流下移向内陆架扩展增强。计算表明,7月纵断面上的净环流输运是盐分纵向净通量的控制因素,输运方向指向上游,而其余季节则以向海的净平流输运为主。悬沙净通量主要受净平流及潮抽吸输运控制,潮抽吸输运强度与大小潮有较密切关系。 相似文献
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珠江河口西南风强迫下潮流场的数值模拟 总被引：1，自引：0，他引：1
采用Backhaus三维斜压模型模拟了均匀西南风场对珠江口近岸海域的影响，并与无风情况作了对比；通过对珠江河口盐度场及风生环流的分析比较，结果表明，模型较为真实地再现了夏季珠江河口的水动力学特性。 相似文献
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Morphology, hydrography and sediment dynamics in a mangrove estuary: The Konkoure Estuary, Guinea 总被引：1，自引：0，他引：1
The Konkouré Estuary in the Republic of Guinea is a poorly understood atypical mangrove system. Sediment dynamics in tropical estuaries are controlled by a combination of processes including river discharge, morphology, salinity, erosion and deposition processes, the settling of mud, physico-chemical processes and mangrove swamps. Here we present a consistent set of data aimed at characterising the estuary and thus, increasing our understanding of tropical systems, as well as studying the impact of human intervention in the region. Water elevations, current measurements, salinity, suspended sediment concentrations, bathymetry and sediment cover are presented following a 3 year survey of the Konkouré Estuary. Here we provide conclusive evidence that the Lower Konkouré is a shallow, funnel shaped, mesotidal, mangrove-fringed, tide dominated estuary, well mixed during low river discharge. The estuary becomes stratified during high river flows and spring tides whereas a salt wedge appears during neap tides. The Konkouré Estuary has been described as hypersynchronous, and has three terminal outlets, two of which are landward-directed, attesting to a tidal pumping effect, while the third one is seaward-directed, and is controlled by the mangrove. The suspended matter is transported by the tidal effect within the middle estuary and is therefore trapped in the Turbidity Maximum zone (TMZ). The location of the TMZ is river-controlled and is correlated with residual currents but not with salinity front. A dam, constructed 130 km upstream, impacts on the hydrodynamics, and reduces the salinity intrusion by about 25%. It causes an increased low river discharge whereas its efficiency over high river flows is unclear. 相似文献
17.
The dynamics in the transition zone between the North Sea and Baltic Sea are analyzed here using data from a 22-year-long climatic simulation with a focus on the periods 1992–1994 and 2001–2003 when two recent major inflow events occurred. Observations from gauges and in situ measurements are used to validate the model. Parameters, which cannot be easily measured, such as water and salt transports through straits, have been compared against similar previous estimates. The good performance of simulations is attributed to the finer resolution of the model compared to earlier set ups. The outflow in the Kattegat, which is an analogue of the tidal outflows, tends to propagate to the North over the shallows without showing a substantial deflection to the right due to the Earth's rotation. The inflow follows the topography. The different inflow and outflow pathways are explained as a consequence of the specific combination of bathymetry, axial and lateral processes. The circulation in Kattegat is persistently clockwise with an eastern intensification during inflow and a western one during outflow regimes. The tidal wave there propagates as Kelvin wave, keeping the coast on its right. The flows in the two main straits reveal very different responses to tides, which are also highly asymmetric during inflow and outflow conditions. The circulation has a typical two-layer structure, the correlation between salinity and velocity tends to increase the salt transport in the salinity conveyor belt. The transversal circulation in the entrance of the Sound enhances the vertical mixing of the saltier North Sea water. The long-term averaged ratio of the water transports through the Great Belt and the Sound is ∼2.6-2.7 but this number changes reaching lower values during the major inflow in 1993. The transports in the straits are asymmetric. During inflow events the repartition of water penetrating the Baltic Sea is strongly in favor of the pathway through the Sound, which provides a shorter connection between the Kattegat and Baltic proper. The wider Great Belt has a relatively larger role in exporting water from the Baltic into the North Sea. A demonstration is given that the ventilation of the Baltic Sea deep water is not only governed by the dynamics in the straits and the strong westerly winds enhancing the eastward propagation of North Sea water (a case in 1993), but also by the clockwise circulation in the Kattegat acting as a preconditioning factor for the flow-partitioning. 相似文献
18.
长江河口波-流共同作用下的全沙数值模拟 总被引：15，自引：1，他引：15
针对长江河口地形、水文、泥沙运动等复杂的特点,建立了波-流共同作用下的二维全沙及河床演变模型.在合理计算研究区域流场等的基础上,利用切应力概念确定悬沙扩散方程中的源函数;通过系列数值试验和实测资料的统计分析,在经典的泥沙临界起动速度中引入反映河床底质结构及固结程度的局地系数;选用由流速、盐度、含沙量浓度确定的泥沙颗粒絮凝沉降速度,从而提高长江口悬沙场数值模拟精度.在底沙输运计算中,提出一种较为合理确定有关参数的方法.通过洪、枯季大、中、小潮水文、泥沙资料和典型台风引起航槽冲淤变化的实测资料验证,表明该文提出的模型能较合理地反映长江河口流场、泥沙场及地形的演变. 相似文献
19.
采用改进的盐度场数值格式模拟珠江口盐度分层现象 总被引：7，自引：0，他引：7
采用基于Backhaus的三维斜压模式计算珠江口水动力特性，重点模拟了夏季丰水期盐度分层现象；改进了原模式的盐度差分格式和方程，采用二阶精度差分格式并引入了物理扩散项。结果表明，改进后的盐度差分方程能较好地反映珠江口盐度成层现象。 相似文献