共查询到20条相似文献，搜索用时 78 毫秒
1.
Yukio Oonishi 《Journal of Oceanography》1977,33(4):207-218
A fundamental mechanism of generation of the tidal residual flow, the steady or quasi-steady flow induced in the tidal current system, is studied by numerical methods. The model basin is a very simple one, a rectangular basin of 5m×10m of constant depth and with a cape of 4 m length jutting out at a right angle from the center of the longer side wall. This basin has the same topography as that studied byYanagi (1976) by means of the hydraulic model experiments.The steady, circular, horizontal current is found to be induced through the following processes. Horizontal friction at the coast makes the vorticity of vertical component in the oscillating flow. Self-interaction of this flow causes the vorticity transfer to the steady flow in frequency domain. This vorticity transfer is confined in the narrow coastal boundary layer. The steady flow advects the transferred vorticity and makes itself develop fully wide over the bay. In other words, there are two kinds of cascade-up, one with regard to time scale and the other with regard to horizontal space scale.When the tidal range, the tidal period and the horizontal eddy viscosity change under the condition that the model geometry is fixed, the nondimensional parameter which controlls the steady flow is found to be the Reynolds number of the oscillating flow. 相似文献
2.
To analyse material transport in inland seas, a horizontal two-dimensional dispersion equation is derived, and the dispersion coefficient due to the combined effect of vertical turbulent mixing and vertical shear of both a steady current and a tidal current is studied. In the present study, the assumption that velocity is uniform in horizontal planes is not necessary, and velocity has a free vertical profile; thus the dispersion coefficient formulated is general, and is represented by a tensor of the second order. The properties of the dispersion coefficient in the horizontal two-dimensional dispersion model are also investigated, and it is shown that the time-averaged dispersion coefficient due to the tidal current over a tidal period is approximately half that due to the steady current, if the velocity amplitude and the vertical profile of the tidal current are the same as those of the steady current (a similar result was presented byBowden (1965) for horizontal one-dimensional models). Finally, the dispersion coefficient in Hiuchi-Nada (Hiuchi Sound) in the central part of the Seto Inland Sea is evaluated by using the model. The values of the dispersion coefficient in that region range from 103 cm2 s–1 to 105 cm2 s–1 when vertical turbulent diffusivity is taken to be 50 cm2 s–1. 相似文献
3.
为了研究人工鱼礁区基本水动力特征,本文利用人工鱼礁投放区的座底海床基获取半年以上的水动力观测资料,通过谱分析、调和分析、滤波等方法分析了该海区潮汐、潮流特征,并讨论了余流特征。结果表明,该海域属于不规则半日潮,具有显著的全日潮周期和半日潮周期,潮汐性质指数为0.98,平均潮差为0.95m,最大可能潮差为2.25m。潮流为典型的往复潮,潮流主向为NNE-SSW,优势分潮为M2分潮。垂向上,流速大小随深度增加显著降低,海底1m的流速较表层降低约30%,流向向沿鱼礁布设方向偏转。该海域余流较小,欧拉余流与斯托克斯余流大小相当,分别为1.35cm/s,1.41cm/s,均为向岸输运,欧拉余流表层受风影响较大,拉格朗日余流为2.76cm/s,方向SEE。该海域流场垂向结构与人工鱼礁投放后底摩擦增加、鱼礁对近底层水流的阻滞作用有关。底层温度具有显著的季节变化与日变化特征,短期高频变化存在显著的全日周期与半日周期,冬春季由于垂向混合加强,全日信号更为显著。底层浊度的升高主要由大风过程加强垂向混合的引起。 相似文献
4.
Two numerical studies (Endoh, 1977;Harashima
et al., 1978) have been proposed on a front formed by a coupling effect of cooling of the sea surface and inflow of the fresh water in a vertical two-dimensional plane without the rotation of the earth. It is, however, not easy to interpret their numerical results. A simple interpretation will be proposed by an analytical study in this paper.It is found that local convection due to the density inversion, which is expressed by the convective adjustment of the vertical diffusion coefficient in the actual numerical calculations, plays an important role on the front formation.The characteristics of the front is also clarified in the case of steady state. Namely, simple functional dependences are obtained of the position and the width of the front, the horizontal and the vertical velocities and the distribution of the buoyancy and the salinity in the neighborhood of the front on the horizontal coordinate, the cooling rate, the eddy coefficients of diffusion and viscosity, the water depth and the vertically averaged horizontal fluxes of buoyancy and salinity. 相似文献
5.
基于长期观测的辽东湾口东部海域水动力特征研究 总被引：1，自引：0，他引：1
辽东湾口东部海域是辽东湾与渤海中部进行物质和能量交换的主要通道之一。本文利用坐底式海床基平台获取的近8个月的水动力连续观测资料,通过谱分析和调和分析方法对该海域的潮汐、潮流特征进行分析,并讨论了余流及底层温度的季节变化规律。研究结果表明:该海域潮汐属于不规则半日潮,平均潮差为0.95 m,最大可能潮差为2.27 m。潮流属于不规则半日潮流,M2分潮流为其优势分潮流。主要分潮流运动形式为往复流,最大流速方向为西南-东北向。余流的季节性特征较为明显:秋季,余流流速在中层达到最大,流向以西南向为主;冬季,余流流速垂向变化较小,并呈西南偏西向流动;春季,流速随深度增加而减小,流向从表层至底层呈现逆时针旋转的特征。受底层潮流、水平温度梯度及海面温度日变化的影响,底层温度表现出短期的高频变化特征:秋季,短期振荡以半日周期信号为主;冬季,全日周期信号较为显著;春季,短期振荡的现象较弱。 相似文献
6.
A thermohaline front is located at the southeastern entrance of the Yellow Sea in winter, and it is generated by the intrusion of warm saline water into the Yellow Sea caused by a strong northerly wind. Recently, a westward transversal current traveling away from the west coast of Korea toward the open sea area along the front was reported. The westward transversal current is dominant in the surface layer during the temperature inversion period. The formation and structure of this current are examined using a numerical vertical ocean-slice model. When two different water masses meet, a front is formed and adjusted geostrophically. In this frontal zone, a horizontal pressure gradient flow by the vertically inclined isopycnal occurs under the thermal wind process in a baroclinic effect, and the cold fresh coastal water moves westward along the front in the upper layer. The barotropic effect across the front and the bottom friction effect strengthen the westward component of the velocity. The velocity of the bottom layer decreases remarkably in the increase of the bottom drag coefficient. This means that the bottom friction with the strong background tidal current causes a reduction in the current in the bottom layer. 相似文献
7.
Ned P. Smith 《Estuarine, Coastal and Shelf Science》1985,21(5):623-632
Current measurements during a 32-day study period in late spring, 1977, are used to quantify the magnitude and relative importance of tidal and wind-driven motion in the interior of the Indian River lagoon, on the Atlantic coast of Florida. Harmonic analysis of the total longitudinal flow along the axis of the lagoon isolates the tidal component of the current; non-tidal flow is revealed by subtracting the tidal current from the total current, and making corrections for non-linear relationships between the current and both surface wind stress and bottom friction. A one-layer, one-dimensional model is developed to simulate wind drift. A quadratic bottom friction term with a drag coefficient of 15 × 10?3 gives results which compare most favourably with observations. Results indicate that tidal forcing explains approximately 45% of the total variance at the study site, 25 km from the nearest inlet. Local wind forcing accounts for 44% of the non-tidal flow. The remainder of the variance is attributed to freshwater outflow through the lagoon and non-local forcing. 相似文献
8.
Three-dimensional structure of tidal current in the East China Sea and the Yellow Sea 总被引：9，自引：0，他引：9
A three-dimensional tidal current model is developed and applied to the East China Sea (ECS), the Yellow Sea and the Bohai
Sea. The model well reproduces the major four tides, namely M2, S2, K1 and O1 tides, and their currents. The horizontal distributions of the major four tidal currents are the same as those calculated
by the horizontal two-dimensional models. With its high resolutions in the horizontal (12.5 km) and the vertical (20 layers),
the model is used to investigate the vertical distributions of tidal current. Four vertical eddy viscosity models are used
in the numerical experiments. As the tidal current becomes strong, its vertical shear becomes large and its vertical profile
becomes sensitive to the vertical eddy viscosity. As a conclusion, the HU (a) model (Davieset al., 1997), which relates the vertical eddy viscosity to the water depth and depth mean velocity, gives the closest results to
the observed data. The reproduction of the amphidromic point of M2 tide in Liaodong Bay is discussed and it is concluded that it depends on the bottom friction stress. The model reproduces
a unique vertical profile of tidal current in the Yellow Sea, which is also found in the observed data. The reason for the
reproduction of such a unique profile in the model is investigated. 相似文献
9.
Takashi Ichiye 《Journal of Oceanography》1970,26(6):340-353
Scaling of the equations of motion of the Antarctic Circumpolar Current indicates that the Rossby number and the Ekman number
are 10−4 to 10−5 but the vertical Ekman number may reach unity in the bottom boundary layer. The equations of motion are integrated vertically
from the surface to the bottom and averaged over a latitude circle. The resulting equation in the meridional direction is
predominantly geostrophic, whereas the main terms of the equation in the zonal direction are the wind stress and the bottom
stress. When the vertical eddy viscosity near the bottom is of the order of 102cm2/sec, the total zonal transport through the Drake Passage computed from the balance of the wind stress and the bottom stress
equals 260×106m3/sec, the amount determined byReid andNowlin (1970) from observations.
The northward transport reduces the eastward transport corresponding to the wind stress of the westerlies in the A. C. C.
through the Coriolis' term in the vertically integrated equation of motion of the zonal direction. South of the Drake Passage,
such reduction reaches about ten percent of the wind-driven transport mainly due to the peripheral water discharge. North
of the Drake Passage, the northward transport may be generated by the effect of the South American coast which prevents free
eastward movement of the A. C. C., causing a wake to the east. This transport may contribute to a part of the northward transport
of the bottom water postulated byMunk (1966). The effect of the horizontal eddy viscosity in the zonal transport equation is negligible except near the Antarctic
coast, if the eddy viscosity is less than 109cm2/sec. 相似文献
10.
长江口浑浊带核心区北槽水动力特征研究 总被引：4，自引：2，他引：2
本文根据2015年长江口洪季浑浊带水域座底三脚架全水深范围观测数据，对北槽中下段纵横向流、余流结构、边界层特征等进行了深入研究，结果显示:（1）大潮潮流矢量特征在垂向上的变化差异最为显著；北槽中下段水流出现明显的横向输移，指向航槽北面；（2）横向流速在大潮期间的变化（垂线平均）为-0.10~0.39 m/s，小潮期间的变化为-0.13~0.25 m/s；横向平流对于北槽纵向物质输运有显著调整作用；（3）余流垂向差异大，底部几乎为0，小潮期间余流更强；周期性再悬浮的细颗粒泥沙可作为北槽最大浑浊带的重要物质来源；（4）传统六点对数流速拟合法获得摩阻流速误差较大，近底1 m区域高分辨流速剖面是准确获取底边界层参数的有效途径。 相似文献
11.
CHEN Yongping 《中国海洋工程》2001,(2):241-252
Based on the fluid motion equations, the physical meaning of eddy viscosity coefficient and the rationality of the Boussinesq hypothesis are discussed in this paper. The effect of the coefficient on numerical stability is analyzed briefly. A semi-enclosed rectangular sea area, with an orthogonal spur dike, is applied in a 2-D numerical model to study the effect of horizontal eddy viscosity coefficient (AH). The computed result shows that AH has little influence on the tidal level and averaged flow velocity, but has obvious influence on the intensity and the range of return flow around near the spur dike. Correspondingly, a wind-driven current pool and an annular current are applied in a 3-D numerical model respectively to study the effect of vertical eddy viscosity coefficient (Av). The computed result shows that the absolute value of Av is inversely proportional to that of horizontal velocity, and the vertical gradient value of Av determines the vertical distribution of horizontal velocity. The distrib 相似文献
12.
Two new types of mechanism for the generation of tidal residual flow are revealed with the use of a hydraulic model experiment. A remarkable anticlockwise tidal residual circulation is formed in a model bay due to the presence of a tidal current, the Coriolis force and a horizontal boundary. A similar circulation is also formed due to the presence of a bottom slope, a horizontal boundary and a tidal current which flows normal to the inclination of the bottom slope. The residual circulation in the Sea of Iyo in the Seto Inland Sea is considered to be due to a combination of the effects of the Coriolis force, a bottom slope, a horizontal boundary and the tidal current. We classified some of the generation mechanisms of tidal residual flow which have been described to date into seven types on the basis of vorticity considerations. 相似文献
13.
Tetsuo Yanagi 《Journal of Oceanography》1979,35(3-4):168-172
Some observations were carried out to understand the structure of the vertical residual flow in Kasado Bay. The results of current measurements at three points in the lower layer indicated that a horizontal counterclockwise tidal residual circulation converges in the lower layer. The velocity of upward residual flow was estimated to be about 4.5×10–3 cm s–1. The distributions of water temperature, salinity and grain size in the sediment support the existence of this upward motion. 相似文献
14.
Effect of hydrodynamic properties of the sea bottom on the tidal dynamics in a rectangular basin 总被引：1，自引：0，他引：1
Expressions derived for the friction coefficient in an oscillatory rotating turbulent bottom boundary layer (BBL) over rough, incompletely rough (smoothly rough), and smooth underlying surfaces are incorporated as an individual module into a two-dimensional nonlinear tidal model, and the standard version of the model and its modified analogue are used to discuss the titular subject. It is established that the dynamics of tides in the Taylor basin can change noticeably under the effect of hydrodynamic properties of the sea bottom. Such changes occur mainly in the influence domains of amphidromies. In the remaining parts of the basin, relative changes in the amplitudes and phases of tidal sea-surface level elevations do not exceed ±10% and ±10°, respectively. The largest discrepancies of tidal characteristics take place in the cases of the incompletely rough and smooth sea bottoms; the smallest discrepancies, in the case of the rough sea bottom. Estimates for the changes in tidal characteristics that are caused by the usually neglected effects of rotation and phase difference between the bottom friction and the tidal velocity at the upper BBL boundary are presented as well. 相似文献
15.
ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｅａｒｌｙ 1 96 0’ｓ,ｔｈｅｔｉｄｅａｎｄｔｉｄａｌｃｕｒｒｅｎｔｉｎｔｈｅＢｅｉｂｕＧｕｌｆｗｅｒｅｏｂｓｅｒｖｅｄａｎｄａｎａｌｙｓｅｄｂｙＣｈｉｎａｉｎｃｏｏｐｅｒａｔｉｏｎｗｉｔｈＶｉｅｔｎａｍ1) .ＴｈｅｓｙｓｔｅｍａｔｉｃｓｔｕｄｉｅｓｏｆｔｉｄｅａｎｄｔｉｄａｌｃｕｒｒｅｎｔｉｎｔｈｅＢｅｉｂｕＧｕｌｆｗｅｒｅｆｉｒｓｔｃａｒｒｉｅｄｏｕｔｂｙＦａｎｇ (1 986 ) .Ｔｈｅｈｉｓｔｏｒｙｏｆｎｕｍｅｒｉｃａｌｓｔｕｄｙｏｆｔｉｄｅａｎｄｔｉｄａｌｃｕｒｒｅｎｔ… 相似文献
16.
在胶州湾湾口、西侧、中心、东侧、北侧湾顶五个区域布设测站,利用2018年冬季至2020年秋季潮位、海流等监测数据,基于最小二乘法进行调和分析计算,并结合垂线平均流速流向、可能最大流速、水质点可能最大运移距离等计算模型,研究分析了胶州湾海流特征。结果表明,各区域潮流类型系数均小于0.5,M2分潮椭圆率绝对值均不超过0.1,接近于0,故胶州湾潮流性质为正规半日潮流,潮流运动形式以往复型为主。湾口区域余流、可能最大流速、水质点可能最大运移位移均最大。不同季节余流流速和流向的差异没有明显的规律性,除湾区西侧测站外,其余位置不同季节余流流向整体上有固定朝向：湾口处东偏北、中心站西偏北、东侧站南偏东、北侧湾顶站东偏北。靠近岸边的湾口、东侧和北侧湾顶站余流流向与邻近海岸垂直。在垂直方向上,各测站可能最大流速和水质点可能最大运移距离由表层至底层整体上呈减小趋势,流向基本一致。 相似文献
17.
D. Myrhaug 《Ocean Engineering》1992,19(4)
The friction velocity associated with the maximum bottom shear stress in neutrally stable tidal planetary boundary layer flow is presented. The directions of the bottom shear stresses for the anticlockwise and clockwise rotating components are also presented. The results are obtained by using similarity theory and are given for flow conditions in the rough, smooth and transitional smooth-to-rough turbulent regime. An approximation for the maximum bottom shear stress by disregarding the rotation of the velocity in the boundary layer as the seabed is approached is also presented. 相似文献
18.
北部湾潮汐潮流的三维数值模拟 总被引：9，自引：1，他引：9
基于二阶湍流闭合模型计算涡动粘性系数的POM三维水动力模式,采用细网格,考虑6个岛屿、海底摩擦系数进行划片取值,模拟北部湾潮汐潮流.所得潮汐调和常数与81个实测站比较,绝对平均误差:K1分潮振幅为46cm,迟角为9°;O1分潮振幅为56cm,迟角为7°;M2分潮振幅为62cm,迟角为15°.由模拟结果分析出该海区潮汐、潮流、余水位和潮余流,以及水平速度垂直分布等特征. 相似文献
19.
A three-dimensional multi-level hydrodynamic model has recently been developed and applied to tidal motion in Singapore’s coastal waters. This paper describes a series of numerical experiments to evaluate the sensitivity of the tidal currents and elevations to model parameters. The results show that the predicted tidal elevations are insensitive to three model parameters: horizontal eddy viscosity coefficient (Smagorinsky constant, ch), bottom friction coefficient (cb) and internal friction coefficient (cv), whereas the effects of these parameters are quite different for tidal current velocities. The velocities are slightly reduced with an increase in ch and cb. The bottom friction effects on velocity profiles increase with water depth. The effect of cv might be significant for the tidal velocities at all levels. The velocities at upper layers of the water column decrease with the increase in cv, whereas the velocities at the bottom layer show the reverse trend. The effects of three model parameters on the magnitude and phase of the simulated currents are in the order (from strong to weak) of cv, cb and ch. 相似文献
20.
The combined tidal and wind driven flow and resulting sediment transport in the ocean over a flat bottom at intermediate water depth has been investigated, using a simple one dimensional two-equation turbulence closure model. This model has been verified against field measurements of a tidal flow in the Celtic Sea. The tidal velocity ellipses and the time series of the horizontal velocity components at given elevations above the bottom are well predicted through the water column although there are some deviations between the predicted and measured velocities near the bottom due to the uncertainty of the bottom roughness. For the combined tidal and wind driven flows the velocity profiles, turbulent kinetic energy profiles and surface particle trajectories are predicted for weak and strong winds. Furthermore, the bottom shear stress and the resulting bedload transport have been predicted; the parts of the particle trajectories in the close vicinity of the bottom where the bedload transport exists are displayed. Finally, the direction and magnitude of the surface drift, the depth-averaged mean velocity and the mean bedload transport are given, and the effect of the bottom roughness on the sea surface drift is investigated. 相似文献