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1.
近40年来珠江口的海平面变化   总被引:5,自引:0,他引:5  
利用大万山附近1°×1°经纬度网格的卫星高度计资料(1993—2006),计算出珠江口绝对海平面的上升速率为0·30±0·05cm/a,与由卫星高度计得出的全球平均海平面的上升速率一致。珠江口各验潮站近40年的潮位变化趋势分析表明,珠江口海平面正加速上升,为全球气候变暖所致;珠江口海平面与全球温度变化和ENSO活动密切相关,一般在ENSO年海平面相对较低。以IPCC有关全球温度上升幅度的预报值和海平面与全球温度变化的关系为依据,预计到2030和2050年珠江口绝对海平面将分别上升6~14和9~21cm,若考虑地面沉降以及波动值,珠江口部分岸段相对海平面将可能分别上升30和50cm。  相似文献   

2.
运用三层嵌套网格的ROMS模式较好地模拟了2009年冬季珠江口的主要水动力过程和盐度分布。结果表明,珠江口盐度层化具有明显的潮周期变化特征,涨潮时表底层盐度差较小,层化较弱;落潮时层化较强。利用势能异常变化平衡方程分析影响层化的贡献项,结果表明势能异常的平流项和应变项是影响珠江口势能异常变化的主要因素。  相似文献   

3.
基于FVCOM模型,将珠江河网、河口和口外海区作为整体,建立完全三维数值模式,对珠江河口及其邻近海域的潮汐进行数值模拟.采用23个潮位站的潮汐表水位资料对模式进行验证,结果表明模式能比较准确地重现珠江河口的潮汐变化过程.通过对计算结果进行潮汐调和分析,给出了珠江河口区域及近岸海域8个主要分潮的同潮图,讨论了潮波的传播特征.珠江河口潮汐属于混合潮类型,潮型系数介于0.8—1.5.浅水分潮成分很小,最大振幅不超过5cm.对珠江河口的潮差进行统计,给出了珠江河口大潮和小潮期间的潮差大小及分布,大潮时潮差介于2.2—3.1m,小潮时减小到0.6—1.1m.  相似文献   

4.
渤海垂直湍流混合强度季节变化的数值模拟   总被引:5,自引:1,他引:4  
渤海为极浅陆架海 ,其中湍流耗散作用显著。将三维斜压陆架海模式 HAMSOM应用于渤海 ,以渤海周边台站每天 4次的常规气象资料作为风和热驱动 ,渤海海峡开边界以 5个主要分潮调和常数计算水位强迫 ,计算了渤海 1982年水文要素和流场变化 ,并用模式以湍的局地平衡理论封闭计算出垂直湍流粘性的时空分布。结果表明 :渤海湍流混合冬强夏弱 ,变化幅度较大 ( 10~ 2 0 0 cm2 / s) ,这是风搅拌和潮混合的湍流输入在密度层化调整下的结果 ;风的作用在冬季强于潮的作用 ,而底层则由潮混合控制呈现半月周期 ;渤海湍粘性系数的空间分布十分复杂 ,这是在渤海地形和岸形轮廓限制下 ,由一定大气条件驱动的流场和密度场导致的湍流混合强度不同所致  相似文献   

5.
珠江河口底边界层湍流特征量研究   总被引:3,自引:0,他引:3  
通过高频流速仪ADV和脉冲相干声学多普勒剖面仪PC-ADP对珠江河口崖门底边界层进行了三个测次潮内(25 h)顶点连续观测,利用观测数据计算分析了潮流底边界层内的湍流特征量及其时空变化.结果表明:1)对于半日潮流占优的河口,各湍流特征量均具有明显的四分之一周日的变化规律;2)湍流强度、床底应力和摩阻流速在潮内的平均值以位于河口湾的测点所测值最大,依次向上游递减,而湍动能耗散率则沿河口湾至上游逐渐增大;3)三个测次边界层内涡动粘滞系数的平均值分别为2.42×10 -3 m 2/s、2.20×10 -4m 2/s和6.16×10 -4 m 2/s,拖曳系数的均值为7.89×10 -3、1.63×10 -3和1.99×10 -2,两者潮内的变化均非常显著,相差可达一到两个数量级;4)在充分混合的潮流底边界层内,湍动能生成与耗散基本处于局部平衡状态,三个测次湍动能耗散率均值在8.89×10 -5 W/kg~7.43×10 -6 W/kg之间.  相似文献   

6.
基于2009年8月17~18日连续25h的21船同步海温观测资料,描述了胶州湾夏季海温的潮内变化特征。观测发现,夏季胶州湾海温自湾口至湾顶的差异显著(ΔT>2.0℃),潮内变化明显(约2.0℃)。海温潮内变化与年际变化幅度相当,这表明使用多船同步观测研究潮内及年际以上尺度变化非常必要,而在使用传统单船非同步观测资料时,需做潮汐订正。经验正交函数和热收支分析表明,海温潮内变化有显著的半日周期,与潮位变化呈明显的负相关关系,潮是海温和胶州湾水体热含量潮内变化的主因,而热含量的潮际变化则受到与黄海的水交换和太阳短波辐射的共同作用。另外,海温的水平分布还受到地形、岸线诱导的海流影响,涨、落潮时黄海水入侵的范围不同即为其主要表现特征之一。  相似文献   

7.
河口湍流数据现场采集和后处理   总被引:1,自引:0,他引:1       下载免费PDF全文
刘欢  吴超羽 《海洋工程》2011,29(2):122-128
利用声学多普勒流速仪ADV,在珠江河口崖门底边界进行了一个潮周期的湍流观测,并选取了急流和憩流两个典型时刻对数据进行后处理分析.后处理方法包括信号检查、过滤和去噪,每个步骤都包含无效数据的剔除和替换.结果表明,后处理对平均流速影响不大,但会显著改变脉动流速统计分布特性.对于河口非定常流动,未经处理的原始数据不适宜用于分析湍流特征量.  相似文献   

8.
任杰  张颖 《海洋学报》2019,41(9):105-113
本文利用2010年枯季在珠江口进行的大、中、小潮LISST剖面及底边界层观测资料,分析了磨刀门河口枯季稳定存在的絮团三峰结构,即构建絮团的基本粒子的平均粒径约为8.3~9.0 μm,小絮团为36~100 μm,大絮团大于180 μm。小潮期,盐跃层捕集的悬浮泥沙以强絮凝过程为主,大絮团含量占优;中、大潮期,平均粒径普遍增大,絮凝占优。潮内的动力变化对絮团多峰结构及形态参数的影响不明显,絮凝与解凝处于动态平衡。结合坐底三角架的湍流资料和简化的群体平衡模型(Population Balance Equation,PBE),进一步揭示了絮团变化的湍流动力机制。高流速下的强紊动剪切力,直接导致大絮团被破坏形成小絮凝体,絮凝体平均粒径减小,反之絮凝强于解凝作用。同时,基于高斯矩积分方法求解PBE,得到的粒径分布基本与观测值吻合,说明在有较好的现场湍流与粒径观测资料的条件下,PBE包含的湍流动力机制可以用来研究黏性泥沙的絮凝过程。  相似文献   

9.
基于ADV声学泥沙反演与扩散机制分析   总被引:4,自引:1,他引:3  
利用座底三脚架观测系统于2012年洪季对珠江黄茅海河口湾底边界层沉积动力过程进行了系统观测,建立了基于现场ADV探测的高频泥沙声学反演方法,分析了泥沙浓度、泥沙扩散通量及泥沙扩散系数随潮汐变化的特征,探讨了泥沙再悬浮的湍流猝发机制。泥沙浓度、泥沙扩散通量、涡动扩散系数及泥沙扩散系数具有明显的潮汐变化特征,主要表现为急流时较大、憩流时较小。泥沙沉降速度与泥沙浓度之间的幂函数关系可以很好地描述潮周期内沉降速度的变化。湍流猝发过程中,喷射和扫射事件是泥沙垂向扩散的主要动量来源,大振幅的猝发事件对泥沙垂向扩散具有决定性影响。  相似文献   

10.
珠江河口潮能通量与耗散   总被引:4,自引:1,他引:3       下载免费PDF全文
珠江河口三角洲是我国一个极其复杂的大尺度河口系统,具有独特的河网体系和河口湾.为探讨珠江河口三角洲的潮能通量和潮能耗散机制,基于SELFE模型,建立了珠江河网-河口湾的三维数值模型,计算了河网-河口湾区的潮能通量和潮能耗散.研究表明:珠江河口的潮能通量平面上表现出主槽大,滩地较小;在总能耗中,底摩擦能耗最大,其次是垂向扩散耗散能耗,水平扩散能耗最小;存在‘门’、分汊汇流区和弯曲河道区等典型的高能耗区,高能耗区的单位面积能耗比附近水域的高数倍甚至1~2个数量级.  相似文献   

11.
各向同性均匀湍流近壁结构及泥沙起动   总被引:4,自引:1,他引:3  
采用振动格栅产生的各向同性均匀湍流研究了泥沙的起动。应用PTV技术和局部光学放大技术对湍流场进行了测量,发现近壁面湍流动能的指数分布规律。分析了泥沙在均匀同性湍流中的起动机制,并用概率统计理论对泥沙的起动进行了定量的描述。通过测定泥沙起动事件的概率,得到了同种泥沙在不同流动参数下起动的临界湍流动能。  相似文献   

12.
The treatment of diffusion due to the tidal current in the near-shore ocean, and the similitude in the hydraulic model experiment are studied.In broad and shallow tidal bays and in the coastal seawaters near irregular boundaries, horizontal eddy-currents induced geometrically and turbulence caused by their cascading have predominant effect on dispersion of river and waste waters. These turbulent diffusion processes are similarly reproduced in the Froude models of turbulent resume, by adding the similitude for the self-similar structure of the spectral density of turbulence, or the eddy diffusivity. The similitude means to take the scale ratios of the time and the vertical length as the two-thirds power of the scale ratio of the horizontal length.Similitudes are also derived for the system of the gravitational circulation, the stratification and the salt-mass transport in partially and well-mixed estuaries. Generally, the vertical eddy diffusivity must be exaggerated by a half power of the model distortion externally by some methods of agitation. When the tidal bay is broad and very shallow, the Rayleigh number and the Hansen number are small, and the effect of density current and stratification on the flushing is small. Instead the effect of local eddies, geometrically induced tidal residual circulations become predominant. In this special case, there is no need to satisfy the similitude for density difference and vertical shear effects on dispersion.  相似文献   

13.
Channel constrictions within an estuary can influence overall estuary-sea exchange of salt or suspended/dissolved material. The exchange is modulated by turbulent mixing through its effect on density stratification. Here we quantify turbulent mixing in Hikapu Reach, an estuarine channel in the Marlborough Sounds, New Zealand. The focus is on a period of relatively low freshwater input but where density stratification still persists throughout the tidal cycle, although the strength of stratification and its vertical structure vary substantially. The density stratification increases through the ebb tide, and decreases through the flood tide. During the spring tides observed here, ebb tidal flow speeds reached 0.7?m?s?1 and the buoyancy frequency squared was in the range 10?5 to 10?3?s?2. Turbulence parameters were estimated using both shear microstructure and velocimeter-derived inertial dissipation which compared favourably. The rate of dissipation of turbulent kinetic energy reached 1?×?10?6?m2?s?3 late in the ebb tide, and estimates of the gradient Richardson number (the ratio of stability to shear) fell as low as 0.1 (i.e. unstable) although the results show that bottom-boundary driven turbulence can dominate for periods. The implication, based on scaling, is that the mixing within the channel does not homogenise the water column within a tidal cycle. Scaling, developed to characterise the tidal advection relative to the channel length, shows how riverine-driven buoyancy fluxes can pass through the tidal channel section and the stratification can remain partially intact.  相似文献   

14.
We observed tidal currents, turbulent energy dissipation and water column stratification at the entrance of a narrow strait (Neko Seto) in the Seto Inland Sea, Japan, using a free-falling turbulent microstructure profiler (TurboMAP) and acoustic Doppler current profiler (ADCP). The variation in turbulent energy dissipation at the entrance of the strait was not at quarter-diurnal frequency but at semi-diurnal frequency; turbulent energy dissipation was enhanced during the ebb tide, although it was moderate during the flood tide. This result is consistent with the results of Takasugi (1993), which showed the asymmetry of tidal energy loss during a semidiurnal tidal cycle using control volume analysis. It is suggested that significant turbulent energy dissipation is generated in the strait, which influences the properties of water outside the strait when tidal currents flow out from the strait.  相似文献   

15.
The bedforms and the local scour at the base of a cylindrical pile were studied in a tidal inlet in the Wadden Sea, southern North Sea, using high-resolution multibeam bathymetry data from four surveys. The observed changes in scour and bedform dimensions were interpreted in terms of hydraulic forcings varying periodically at different time scales. It appears that bedform orientation reacts to changing flow conditions on a semidiurnal basis, whereas bedform height and steepness reflect the spring-neap cycle as well as seasonal signals. The scour depth carries a strong overprint of the semidiurnal tidal cycle, which is at a maximum during the strongest tidal flow. Subtler variations in scour depth can possibly be attributed to the spring-neap tidal cycle. Based on these data on bedform and scour dimensions, correlation functions were established between scour depth and dune height as well as dune length. In measuring the scour depth under mobile bed conditions, establishing the seabed level based on the trough level of the bedforms nearest to the scour proved useful. These findings suggest that the dimensions of bedforms in dynamic equilibrium with prevailing hydraulic flow conditions can be used to estimate scouring in tidal environments.  相似文献   

16.
远海航渡式水深测量水位改正方法研究   总被引:1,自引:0,他引:1  
针对远海航渡式水深测量作业中的潮汐改正难题,基于全球潮汐场DTU10模型及GPS无验潮测深两种改正模式,通过潮汐场预报精度评估、验潮站实测数据比对分析以及GPS大地高计算潮汐值等多种手段,开展了大范围、长时段、单测线情况下水深测量水位改正研究,形成了一套适用性强的航渡水深测量水位改正方法与流程,为面向全球的海洋水深测量资料处理提供了潮汐、垂直基准和水位归算的方法和技术支持。  相似文献   

17.
天然感潮河道水流紊动特性分析   总被引:5,自引:0,他引:5  
采用多谱勒三相流速仪,在长江口徐六泾水文观测断面分别进行了涨潮、落潮时中泓与近岸垂线的流速观测,根据这些观测资料,对天然感潮河段潮流紊动的周期、频率、概率密度函数等进行了定量的数学描述,并对时均流速、紊动强度、雷诺应力等沿垂线分布进行了分析计算。  相似文献   

18.
湍流数值模拟中封闭模式应用的局限性   总被引:1,自引:0,他引:1  
通过对琼州海峡的潮流场特征进行数值模拟,指出了选择不同的特征混合长度表达式对数值模拟结果的影响,表明了基于特征混合长度理论的流封闭模式在近海湍流数值模拟中应用的局限性。  相似文献   

19.
将一个三维湍能封闭模型应用于渤海潮流模拟,通过流速分解的初边值方法,计算了渤海全海区潮波系统、潮流结构,结果与观测符合较好。计算同时给出了湍粘性系数和湍动能的时空分布,比较常湍粘性系数和湍的垂直抛物分布及湍能封闭模拟表明,湍粘性系数的不同选取会对流场结构有显著影响。  相似文献   

20.
The paper presents an analysis of laminar and turbulent flow in porous stone material in order to evaluate the order of magnitude of scale effects in hydraulic models. Hydraulic model tests, such as for example breakwater model tests, are normally carried out at such small scales that the flow through the various layers of the breakwater is not completely turbulent. For this reason scale effects occur. A well-known method to compensate for the scale effects is to use larger stones than calculated by Froude's model law in certain regions of the model. The paper presents formulae for the calculation of the compensated stone sizes based on earlier work by Engelund. Further an evaluation of the energy dissipation in hydraulic models is made in order to determine the scale effect due to “laminar” flow.  相似文献   

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