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Yoshihiro Mazda 《Journal of Oceanography》1984,40(3):199-206
The year-to-year change in characteristics of water exchange between Lake Hamana, a semi-enclosed bya, and the adjacent open sea is investigated.The destruction of the bay mouth by a typhoon in 1953 and subsequent stabilization work on the bay mouth from 1954 to 1973 resulted in an increase in the tidal prism volume of the bay (Mazda, 1983). In the present paper, a simple model has been constructed in which the magnitude of water exchange depends on the tidal prism, and using this model, the year-to-year increase in salinity of the bay water after 1953 can be well explained. Consequently, it can be said that the salinity increase after 1953 is a result of a progressive increase in water exchange caused by successive changes in topography of the bay mouth.The extent of water exchange in Lake Hamana, which varies seasonally, has increased gradually since 1953, and became stable after about 1967. For instance, at present the turnover time of the bay for exchange with open sea water reaches a maximum (2.9 months) in January and a minimum (0.9 month) in October, while in 1955 it is estimated to have been about 2.5 times that at the present time. 相似文献
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象山港潮滩坡度对潮动力影响的数值研究 总被引:2,自引:0,他引:2
象山港属于狭长型半封闭港湾,湾内分布有大面积潮滩。多年以来象山港内实施了大量海岸工程及养殖工程,湾内潮滩坡度发生了显著变化。基于非结构网格和有限体积数值模式(FVCOM)建立象山港三维潮动力模型,研究湾内不同区域潮滩坡度变化对象山港潮动力过程的影响机理。结果表明:潮滩坡度下降将增大湾内纳潮量,进而增大M2分潮振幅和迟角,反之则反。铁港潮滩坡度的减小(增大),将改变底部耗散项,进而增大(减小)M4分潮振幅。由于M2和M4分潮的振幅在湾顶较大,所以湾顶(铁港)潮滩坡度对象山港潮动力过程的影响明显大于侧岸(西沪港)。西沪港潮滩坡度对象山港潮动力过程的影响是局部的。铁港、西沪港潮滩坡度对湾内潮汐不对称、余流及潮能影响显著。铁港潮滩坡度的改变均会减弱湾内落潮占优程度。西沪港区域潮滩坡度的减小将减弱湾内落潮占优趋势,反之则反。铁港和西沪港潮滩坡度的减小,将增大余流大小及潮能密度,进而潮能耗散增大,反之则反。研究结果对河口海岸潮滩区域的工程建设及生态修复有重要参考价值。 相似文献
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作为半封闭狭长海湾,铁山湾受风暴潮灾害的影响较为严重。根据多年观测资料和数值模型对铁山湾内的风暴潮水位特征进行了研究。观测资料表明海湾内风暴潮峰值水位受天文潮相位影响较为显著,然后基于ADCIRC风暴潮模型和1409号“威马逊”台风参数,定量评估了天文潮对风暴潮水位的影响。模拟结果表明当考虑天文潮作用时,会显著提高模拟结果精度,然后通过数值实验研究了风暴潮与不同相位天文潮相互作用时的水位变化特征。数值实验结果表明天文潮-风暴潮相互作用引起的非线性水位在涨潮阶段不明显,在高潮位时非线性水位达到负值最大;在落潮时达到正值最大。风暴潮增水峰值由于受到这种非线性效应的影响,在高潮位时数值最小。海湾内非线性作用要远大于外部,非线性效应越强,总水位峰值相对于天文潮高潮位的延迟时间也就越长。 相似文献
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海湾内外的潮波变形及其不对称性影响海湾内外动力输送和水体交换。利用乐清湾内外共9个测站连续潮位进行调和分析,得到该海湾内外各分潮变化规律,利用潮不对称性偏度计算方法确定湾内外潮汐不对称性时空变化特征,比较了主要分潮组合对潮汐不对称性的贡献度,通过数值研究探讨了湾内偏度比湾外偏度值更小的主要成因,分析了湾内外围垦工程对潮不对称偏度的影响。研究发现:乐清湾内潮汐不对称偏度值为负,表现为落潮占优,同期湾外洞头站偏度值为正,与邻近瓯江、飞云江河口的潮不对称偏度变大、表现涨潮占优的变化规律相反;湾外沿岸各站偏度由东北向西南逐渐增大,由落潮占优向涨潮占优变化;潮汐不对称性偏度呈周期性变化,分析确定M2-M4、M2-S2-MS4分潮组合对潮不对称贡献大,该海域潮汐不对称的强度主要由浅水分潮振幅控制,而相对相位则决定潮汐不对称的方向;数值研究探讨表明,湾内大范围的浅滩地形是其潮汐不对称落潮占优的主要原因,围垦将削弱湾内的落潮占优。 相似文献
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象山港内三维动边界潮流的数值模拟 总被引:1,自引:1,他引:0
象山港是一具有广阔潮滩和大潮差区域的半封闭型海湾,进行数值模拟时必须引入动边界技术来考虑露漫滩的影响.在二维模式中引入动边界技术相对成熟一些,而将这些二维模式使用的露漫滩处理方法简单地搬入三维模式中,常遇到由于边界不连续变动而产生的数值"噪音"及计算不稳定现象.原始POM(Princeton ocean model)模型采用固定边界,没有使用动边界技术,故无法模拟漫滩流.借鉴BURCHARD et al 2004年的研究工作,在原始POM模型的基础上,突破其为固定边界模式的局限,基于尽量使模式物理上满足流动简化需要的原则,引入了一种较为自然的动边界处理技术,使得在非常浅水处和复杂的地形情况下,应用合理的数学表达式体现该物理过程.当总水深大于设定的临界水深时,体现的数学方程是通常形式的动量方程;而当总水深接近设定的最小允许水深时,模型的动量方程被简化为变化率、摩擦力和正压梯度等项之间的平衡关系,此时由于摩擦力占优,相应的流速也会趋于0,这样可以有效避免计算中出现负水深.除在非常浅水处对动量方程作简化外,对于陡坡地形附近的露漫滩问题,当发生一个网格点上的水位低于相邻格点海床的现象时,还需对正压梯度的求解作一个简单的数值处理,以避免不合理值的出现.此外,通过修改原始POM模型的底摩擦系数表达式,可使模型在模拟露漫滩过程时计算更加稳定.改进后的POM模型被用来模拟象山港海域内的三维潮流场,模型计算结果与2个潮位站、1个锚系站和2个船测连续站资料进行了比较,符合良好.整个模型很好地再现了象山港内大区域三维涨、落潮流特征和变化规律,同时象山港顶区域涨憩、落急、落憩和涨急4个特征时刻的流场水平和垂直分布变化过程反映该模型能很好地反映涨、落潮造成的潮间带的露漫滩过程,由此说明对原始POM模型所作的修改是十分有效和可行的,有利于进一步扩充POM模型的应用范围. 相似文献
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The Princeton Ocean Model with realistic bottom topography has been used to investigate the summer temperature decrease in
the past 25 years in Fukuoka Bay. The vertical mixing of the model is expressed by a scheme that effectively includes the
influences of interannual variations of tidal currents and wind. The results show that the historical temperature decrease
in summer has been caused by tidal currents and wind weakening in the past 25 years in Fukuoka Bay. The weakening of tidal
currents and wind gives rise to weakening of the vertical mixing, and to enhancement of the estuarine circulation in the bay.
The enhancement of the estuarine circulation activates the inflow of open-ocean water toward Fukuoka Bay. Coastal water in
summer has therefore tended to be colder and more saline in the past 25 years. This interannual variation in coastal waters
is called “open-oceanization” in this study. On the basis of the numerical model, it is anticipated that the temperature will
decrease by 0.2°C in the next 25 years in Fukuoka Bay if the tide and wind weaken persistently as in the present bay. 相似文献
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A Computational Model for Velocity Separation in Shallow Sea 总被引:1,自引:0,他引:1
Based on the hydrodynamical feature and the theoretical velocity profiles of tidal flow and vvind-induced flow in shal-low sea, a computational model is established for the first time, which can separate observed velocity into tidal velocity and wind-induced velocity by use of the least square method. With the model, not only the surface velocities of tidal flow and vvind-induced flow are obtained, but also the bed roughness height is determined and the wind velocity above the wa-ter surface is estimated. For verification of the model, the observed velocity in the Yellow River Estuary and the laborato-ry test is separated, then it is applied to the Yangtze River Estuary. All the results are satisfactory. The research results show that the model is simple in method, feasible in process and reasonable in result. The model is a valid approach to analysis and computation of field dala, and can be applied to separate the observed velocity in shallow sea; at the same time, reasonable boundary conditions of th 相似文献
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1 .IntroductionThe development and application of hydrodynamic models to predict circulation in estuarine ,coastal ,and shelf waters has been extremely active over the past three decades (Spauldinget al .,1992 ,1994) . However , most of these models are b… 相似文献
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To clarify the time change in water exchanges between Ise Bay and the adjacent ocean, repeated hydrographic observations were
conducted along the longitudinal section in Ise Bay. The results show that the mixing condition at the bay mouth (Irago Strait)
changed fortnightly in summer. During the spring tides, the strait water below the pycnocline was well-mixed and nearly homogeneous.
By contrast, it was weakly stratified during the neap tide. There is a strong negative correlation between the tidal range
and the density difference between the upper and lower layers at the strait. In summer, the intrusion depth of oceanic water
into the bay and consequent hydrographic conditions inside the bay changed frequently according to the tidal strength. During
the spring tides a prominent bottom front was created at the bay mouth, indicating that the strait water, which is a mixture
of oceanic and bay waters, intruded through the middle layer. On the other hand, during the neaps, cold and saline oceanic
water intruded through the bottom layer into the bay. The intrusion depth is significantly correlated with the tidal range.
It is considered that the wellmixed strait water, which has a density equivalent to the middle layer inside the bay, is lighter
than the bottom bay water and thus intrudes through the middle layer during the spring tides, while insufficient mixing makes
the bottom water at the strait heavier than the bay water, leading to the bottom intrusion during the neap tides. 相似文献
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象山港水交换数值研究 Ⅱ.模型应用和水交换研究 总被引:25,自引:4,他引:21
使用水平二维对流-扩散型水交换模式模拟研究了象山港的水交换,对不同区域的水交换控制机理作了初步探讨,象山港水交换状况与其控制机制的区域性变化很大。牛鼻水道至佛渡水道是一个潮流较强的潮通道;90%水交换周期为5天左右。象山港狭湾内水交换周期较长,湾顶处90%水交换的周期约为80天左右。 相似文献
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一个概化的潮汐河口羽状流动力学的初步研究 总被引:1,自引:0,他引:1
基于区域陆架海水动力-生态耦合模型(COHERENS)中的三维水动力模型,对一个概化的潮汐河口羽状流动力学进行了初步研究。在均一水深和无风的理想条件下,模拟得到了一个潮周期内概化的潮汐河口表层水体:a)羽状流流场和盐度场的平面分布;b)3种不同河流径流量作用下的羽状流流场和盐度场的平面分布;c)4种不同底床粗糙长度下的羽状流流场和盐度场的平面分布。结果分析表明:a)羽状流的长度在潮汐的作用下递增,而其最大宽度近似呈周期性的变化;b)羽状流的长度和最大宽度都随着河流径流量的增大而分别变长和变宽;c)羽状流的长度和最大宽度都随底床粗糙长度的增大而变小;d)无潮情况下羽状流的凸起明显并存在沿岸流,然而在有潮情况下凸起不明显且无沿岸流;e)水平扩散可能限制了沿岸羽状流的发展。 相似文献
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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
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基于非结构三角形网格、干-湿判别技术和有限体积法的FVCOM(finite volume coastal oceanmodel)海洋数值模式,建立了厦门湾及其周边海域高分辨率(30 m)的三维潮汐、潮流数值模型.模拟结果同该海域2个验潮站和4个连续海流站的观测资料符合良好,较好地反映了厦门湾及其周边海域潮汐、潮流运动的变化状况和分布特征,并给出了M2、S2、K1、O1共4个主要分潮的同潮图、表层潮流椭圆、最大可能潮流流速及表、底层潮余流分布.厦门湾及其周边海域属正规半日潮类型,4个分潮的最大潮汐振幅分别为200、65、36、29 cm,厦门湾内外迟角差分别为20°、25°、18°、10°;镇海角至围头角连线东南侧湾口区为逆时针旋转的驻波,西北侧湾内为前进潮波.湾内潮流属正规半日潮流,湾口区潮流以逆时针方向的旋转流运动为主,湾内各水道为往复潮流,椭圆长轴与水道走向一致,4个分潮流表层最大流速分别为201、51、34、25 cm/s;九龙江口区3条港道内的流速以南港最大;表层余流大于底层余流,二者水平分布形态基本一致,都为北进南出. 相似文献