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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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ECOM模式在丁字湾的应用 总被引：3，自引：3，他引：3
应用河口、陆架和海洋模式 (ECOM模型 ) ,引入干湿网格法模拟潮滩涨落的改进 ,并建立丁字湾及近岸海域的三维变动边界潮流模型。该模型考虑了湾口拦门沙、湾内水道和人工围海等地形特点。计算结果与实测值比较符合良好 ,较好地刻画出丁字湾 M2 分潮潮流场的时空分布特点。 相似文献
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《中国海洋大学学报(自然科学版)》2010,(Z1)
采用有限体积三维近岸海洋模型,建立无结构三角形网格,对当今地形下的黄河口海域进行高分辨率数值模拟,在成功模拟渤海潮汐潮流的情况下,重点研究了黄河口海域。当前黄河口附近海域潮汐为不规则半日潮,潮流为往复流,方向近似平行于岸界,潮致欧拉余流在岬角两侧存在成对的涡旋,涡旋的方向为南顺北逆,黄河径流对此涡旋有加强的作用。由于地形等复杂因素的影响,河口海域附近在涨落潮转换过程中存在内涨外落型和内落外涨型切变锋,其首先出现在浅水区域,然后向深水区域传播,1~2 h后消失,它的产生是由于近岸海域潮汐相位领先于外海海域潮汐相位。 相似文献
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基于对POM(Princeton Ocean Model)模式的改进,采用Flather-Heaps干湿网格法和两重网格嵌套的数值计算格式,针对天津近岸海域的地形和易受风暴潮漫滩灾害侵袭的特点,建立了天津近岸海域三维动边界风暴潮漫滩模型,对天津近岸区域台风影响下的风暴潮漫滩进行了数值模拟研究。选取7203,8509,9216,9711号典型台风过程,计算了风暴潮漫滩水位变化,通过与塘沽站点实测数据的比较,计算的增水曲线过程与实测结果吻合较好,基本能够真实反映天津近岸的风暴潮水位变化情况及漫滩范围。研究结果验证了改进POM模式为动边界数值模型并应用于浅海区域是可行性的。 相似文献
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《海洋通报(英文版)》2016,(1)
采用有限体积三维近岸海洋模型,建立无结构三角形网格,对当今地形下的黄河口海域进行高分辨率数值模拟,在成功模拟渤海潮汐潮流的情况下,重点研究了黄河口海域。当前黄河口附近海域潮汐为不规则半日潮,潮流为往复流,方向近似平行于岸界,潮致欧拉余流在岬角两侧存在成对的涡旋,涡旋的方向为南顺北逆,黄河径流对此涡旋有加强的作用。由于地形等复杂因素的影响,河口海域附近在涨落潮转换过程中存在内涨外落型和内落外涨型切变锋,其首先出现在浅水区域,然后向深水区域传播,1~2 h后消失,它的产生是由于近岸海域潮汐相位领先于外海海域潮汐相位。 相似文献
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基于MIKE FLOOD建立秦皇岛入海河流及其近岸海域一维、二维耦合河流-海岸水动力和水质模型,研究了秦皇岛海域和入海河流的水动力和污染物分布规律。结果表明:(1)海域潮流为半日潮,其中石河口南北支入海口流速变化过程差别较大,但水位变化过程基本一致;(2)整体上河流入海口化学需氧量(COD)与流速呈正相关关系;(3)COD在近岸海域的扩散方向与涨落潮潮流方向一致,各入海河口海域落潮流期间的COD高于涨潮流。如上结论为赤潮爆发机理和应急处置研究提供科学依据和技术支持。 相似文献
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基于美国普林斯顿大学的POM(Princeton Ocean Model)模型,将干湿网格技术引入到模型中,利用模型的外模式(二维)对深圳湾海域的潮汐、潮流和余流进行了数值模拟研究。模拟结果与实测值吻合较好。计算结果表明:深圳湾海域属不正规半日潮,水平潮流具有明显的往复流性质,主要呈西南—东北走向;落潮流速略大于涨潮流速;受地形及陆地河流径流的影响,湾中到湾口及航道附近流速较大,湾顶和靠近香港的滩涂部分流速较小;深圳湾余流场较弱,余流流向指向湾外;整个深圳湾水交换较弱,海域自净能力较差。 相似文献
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针对河口地区潮流特点,建立了潮流量推算一维水动力数学模型。该模型将Sa in t-V enan t方程组进行求解,并根据涨、落潮流的水动力特性,分别进行涨、落潮糙率率定,准确计算出逐时段河道各断面的水位和流量。应用该模型对宁波三江口地区的潮流量进行推算,结果表明,计算的潮流量与该地区实测的潮流量吻合得较好。 相似文献
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Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
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Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations. 相似文献
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Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans 总被引：1，自引：0，他引：1
A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level. 相似文献
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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献