A three-dimensional multi-level turbulence model for tidal motion

A three-dimensional multi-level turbulence model is developed to simulate tide induced circulation in coastal waters. Based on the bathymetry data, the coastal waters are divided into a number of layers. In every layer, the velocities are integrated along the layer depth. The eddy viscosity and diffusivity are computed from the Prandtl mixing length turbulence model. This multi-level model solves for the water surface elevations and currents in different water depths. Comparison of numerical results with the measured data shows good conformity.     

Seasonal Variation in Lower Trophic Level Ecosystem of Hakata Bay, Japan

The seasonal variation in lower trophic level ecosystem of Hakata Bay, Japan is investigated using observed data from April 1993 to March 1994 and a numerical ecosystem model. Primary production was largest in September 1993 due to high DIP concentration but secondary production was largest in August 1993 due to high water temperature. Yearly averaged primary production in Hakata Bay is larger than that in the Seto Inland Sea but yearly averaged secondary production in Hakata Bay is smaller than that in the Seto Inland Sea. New production was nearly the same as regenerated production in summer but the former was larger than the latter in winter. Yearly averaged ratio of new production to regenerated production in Hakata Bay is larger than that in the open ocean.     

象山港围隔生态系水质模型研究

在美国环保局开发的WASP(the water quality analysis simulation program,水质分析模拟程序)中的概念模型基础上,运用系统动力学软件Stella9.0.2建立了适用于海洋围隔生态系水质动力学模型.模型包括浮游植物、磷循环、氮循环、碳生化需氧量-溶解氧4个模块,涉及叶绿素a、有机磷、无机磷、有机氮、氨氮、硝酸-亚硝酸盐氮、生化需氧量、溶解氧8个水质指标.利用2010年10月初象山港围隔生态实验数据进行了模型验证和参数率定工作,成功模拟了不同水温条件下围隔水质情况,并确定了30余个模型参数,展现了系统动力学模拟的优势,为揭示象山港海域生态系统的动力学机制,模拟和预测他的变化提供科学依据.     

湄洲湾海域夏秋季水质状况

１９９２年夏季和秋季对湄洲湾海域水质进行两期的调查研究，除观测主要水文气项目外，重点调查水化学要求，监测项目：盐度、ＰＨ、溶解氧、化学耗氧量、生化需氧量、无机氮、活性磷、石油类等。本文将调查数据整理分析。     

浮山湾帆船基地海域水质变化预测及分析

在对青岛浮山湾帆船基地海域水质现状分析评价的基础上, 利用二维平流-扩散模型, 选取化学需氧量(Chemical oxygen demand, 简称COD)作为水质指标因子, 按麦岛污水处理厂改造扩建前、改造扩建后正常运行及改造扩建后事故运行3 种情况, 对污水排海给帆船基地海域水质带来的影响进行了预测和分析。由3 种情况预测结果可以看出: 1)麦岛污水处理厂改造扩建后, 大大改善浮山湾帆船基地周围海域的水质情况; 2)麦岛污水处理厂改造扩建后, 正常运行情况下入海COD 对帆船基地海域水质的影响不大, 海水中COD 浓度未出现超一类海域水质要求的情况; 在事故运行情况下入海COD 在排污口附近有超一类海域水质的现象, 面积最大为2 674 m², 未出现超二类以上海域。     

浮山湾帆船基地海域水质变化预测及分析

在对青岛浮山湾帆船基地海域水质现状分析评价的基础上,利用二维平流．扩散模型,选取化学需氧量（Chemical oxygen demand,简称COD）作为水质指标因子,按麦岛污水处理厂改造扩建前、改造扩建后正常运行及改造扩建后事故运行3种情况,对污水排海给帆船基地海域水质带来的影响进行了预测和分析。由3种情况预测结果可...     

A three-dimensional water quality model and its application to Jiaozhou Bay, China

A three-dimensional coupled physical and water quality model was developed and applied to the Jiaozhou Bay to study water quality involving nutrients, biochemical oxygen demand, dissolved oxygen, and phytoplankton that are closely related to eutrophication process. The physical model is a modified ECOM-si version with inclusion of flooding/draining processes over the intertidal zone. The water quality model is based on WASP5 which quantifies processes governing internal nutrients cycling, dissolved oxygen balance and phytoplankton growth. The model was used to simulate the spatial distribution and the temporal variation of water quality in the Jiaozhou Bay for the period of May 2005 to May 2006. In addition, the effect of reduction of riverine nutrients load was simulated and evaluated. The simulated results show that under the influence of nutrients discharged from river, the concentrations of nutrients and phytoplankton were higher in the northwest and northeast of the bay, and decreased from the inner bay to the outer. Affected by strong tidal mixing, the concentrations of all state variables were vertically homogeneous except in the deeper regions where a small gradient was found. Obvious seasonal variation of phytoplankton biomass was found, which exhibited two peaks in March and July, respectively. The variation of riverine waste loads had remarkable impact on nutrients concentration in coastal areas, but slightly altered the distribution in the center of the bay.     

Water quality in Sepetiba Bay,Brazil

Sepetiba Bay is located at 23 degrees S, 44 degrees W in Rio de Janeiro State, Brazil. Water samples were taken at eight locations adjacent to the north shore of the Bay, near to villages and towns without sewage treatment provision. The samples were analysed and total and faecal coliform concentrations determined. A hydrodynamic model of the Bay was used together with a species dispersion model based on an adaptive quadtree mesh to predict faecal concentrations in the Bay. Effluent sources used in the model were defined using population data from census returns with flow and concentration values estimated using standard values recommended by the World Bank (WB) and the World Health Organisation (WHO). Sufficient agreement was obtained between the measured and predicted concentrations to support the use of WB and WHO summary statistics to estimate sources of sewage.     

A study of hydrodynamics of three-dimensional planing surface

The hydrodynamic problem of 3D planing surface is studied by a finite element approach. The planing surface is represented by a number of pressure patches whose strengths are constant at each element. The unknown pressure strength is obtained by using the free surface elevation condition under the planing surface and Kutta condition at the transom stern. Previous studies indicate that, when the constant pressure distribution method is used, the number of buttocks should be less than five or six, otherwise the calculated pressure distribution will start to oscillate and even become divergent. In the present study, after careful examination of the influence coefficients, it is found that the accuracy of the influence coefficients matrix is very important to the convergence of the solution, especially when the number of elements is relatively high. The oscillation of the pressure distribution can be avoided by constant element method if the influence coefficients are sufficiently accurate. The predicted results of the present paper with more number of buttocks are in good agreement with other researchers'. It is concluded that the irregularity of the pressure distribution found in previous studies is most likely caused by the low accuracy in their calculation of the influence coefficients, not by the method itself.     

水东湾潮流特征分析及三维数值模拟

基于水东湾海域利用现状及水环境综合整治工作的迫切需要,对其海洋水文要素开展野外调查,以清晰理解其潮流特征,并据此进行潮流三维数值模拟.调查结果显示,水东湾观测期间的实测潮差在2.6~2.9 m之间,平均潮差约2.8 m,湾口潮差最大,湾顶海域潮差最小,涨潮历时略长于落潮,属不正规半日潮;各观测站位的最大流速相差较大,最高值出现在湾口深槽,为134 cm/s,最低值出现在湾顶浅海海域,为31 cm/s,最大流速水平分布基本上呈现为从湾口向湾顶递减态势.模拟结果显示,水东湾内潮流基本沿潮汐通道呈往复流动,涨潮流向介于280°~300°之间,流速在0.28~1.36 m/s范围内变化;落潮流向介于128°~180°之间,流速在0.56~1.44 m/s范围内变化,流矢受地形限制显著.     

Large scale three-dimensional seepage analysis model test and numerical simulation research on undersea tunnel

During the construction process of Qingdao Jiaozhou Bay Undersea Tunnel, the faults and other unfavorable geological discontinuities were often encountered. To study the water inrush mechanism in the faults, both physical model test and numerical analysis were carried out. The results of crown displacement and hydraulic pressure of the monitoring sections in the physical model and numerical model were analyzed in this paper. It was found that the displacement and hydraulic pressure in the process of tunnel construction are often interacted as both cause and effect, and the lower of hydraulic pressure is often accompanied with the growth of its displacement. The changing of the excavation disturbed zone during the excavation in the undersea tunnel was also studied. The results show that the excavation disturbed zone in fault is larger than that in surrounding rock mass, and the excavation disturbance effects in the filling type fault are both transient and persistent. When the displacement and hydraulic pressure in the undersea tunnel change sharply during excavation, there are relatively slow and continuous change trend of the displacement and hydraulic pressure. For practical purposes, to prevent water inrush in the undersea tunnel, more attentions should also be paid to the undersea tunnel after excavation.     

A numerical study of three-dimensional wave interaction with a square cylinder

In this study, a three-dimensional numerical model is used to study the wave interaction with a vertical rectangular pile. The model employs the large eddy simulation (LES) method to model the effect of small-scale turbulence. The velocity and vorticity fields around the pile are presented and discussed. The drag and inertial coefficients are calculated based on the numerical computation. The calculated coefficients are found to be in a reasonable range compared with the experimental data. Additional analyses are performed to assess the relative importance of drag and initial effects, which could be quantified by the force-related Keulegan and Carpenter (KC) number: KC_f=UT/(4πL). Here U is the maximum fluid particle velocity, T the wave period and L the length of structure aligned with the wave propagation direction. For small KC_f, the effective drag coefficient is proportional to 1/KC_f, provided the wavelength is much longer than the structural length. When wavelength is comparable to the structure dimension, the effective drag coefficient would be reduced significantly due the cancellation of forces, which has been demonstrated by numerical results.     

厦门港潮动力的数值模拟

本文建立了一个计算厦门港潮动力的数值模式,计算方法以ADE方法为原型,用E-L方法加以改造,适用于厦门港动边界模式的计算。经过验证,得到较好的潮汐潮流的模拟结果。计算余流的结构清晰可见,较准确地反映了厦门(?)的潮余流趋势。     

Seasonal Variations in Nutrient Budgets of Hakata Bay, Japan

Seasonal variations in freshwater, salt, phosphorus and nitrogen budgets of Hakata Bay, Japan were investigated from April 1993 until March 1994. The internal sink of dissolved inorganic phosphorus (DIP) and nitrogen (DIN), and the internal source of dissolved organic phosphorus (DOP) and nitrogen (DON) predominate in the bay. This means that the production of organic matter is larger than respiration, and atmospheric CO₂ is absorbed in the water column of Hakata Bay. Denitrification is more dominant than nitrogen fixation in the bay. Compared to Tokyo and Mikawa Bays, Hakata Bay is harder to eutrophicate, mainly due to the shorter residence time of freshwater.     

The study on three-dimensional numerical model and fronts of the Jiulong Estuary and the Xiamen Bay

Applying the methods of on-site observation and dynamic model, the research on the fronts at the Jiulong Estuary has been carried out, during which spatial and temporal distribution, dynamic characteristics and formation mechanism of salinity fronts are analyzed and discussed. The research shows that the estuarine fronts mainly lie in the area from the Jiyu Islet to the Haimen Island, outside of Yuweizai to Hulishan cross-section, the near coast of Yuweizai and the south of the Songyu-Gulangyu Channel. The fronts in the former two regions are formed directly by plume, while the one near the coast of Yuweizai is a tidal intrusion front caused by flood current and the one at the south of the Songyu-Gulangyu Channel is the result of current shear transformation. Under normal circumstances, fresh water of the Jiulong River mainly influences the inside of the Xiamen Bay, and when it is in typhoon seasons, plume front can affect the Taiwan Strait and has an effect on the biogeochemical processes in the strait.     

基于改进的RCA水质模型对珠江口夏季缺氧及初级生产力的数值模拟研究

针对珠江口藻类生长受泥沙遮光限制明显的问题, 对RCA(row and column of Aesop)三维水质模型进行改进, 加入泥沙模块及悬沙遮光对藻类生长的限制作用。应用改进的RCA水质模型, 对珠江口的营养盐、浮游植物及溶解氧进行模拟研究, 结果显示, 改进的RCA水质模型较好地再现了洪季珠江口营养盐、浮游植物和溶解氧在水平及垂向上的空间分布, 这表明该水质模型能较好地反映珠江河口中生态因子的关键过程。珠江口的缺氧现象在物理和生化过程的共同作用下, 被限制在伶仃洋的西滩和中滩及磨刀门海域。在洪季, 大量冲淡水进入珠江口形成锋面, 颗粒态有机物(particulate organic matter, POM)在锋面的影响下, 大量集中沉降在伶仃洋的西滩及中滩特定区域及磨刀门外, 产生较高的底泥耗氧率(sediment oxygen demand, SOD)。而在高SOD的区域, 水体分层通常也较明显, 因而产生缺氧现象。另一方面, 伶仃洋水体中磷的限制作用明显, 加上悬浮泥沙的遮光作用, 不利于浮游植物生长, 使得初级生产力低; 而在陆架上, 悬沙浓度减少使初级生产力增加, 但由于海源颗粒有机碳(particulate organic carbon, POC)的沉积分散于整个陆架上, 无法产生伶仃洋内的高SOD区域, 加上水体分层不明显, 并没有产生缺氧现象。     

辽东湾入海河流水质时空变化与污染物来源分析

基于辽东湾入海河流120个监测断面（含16个入海断面）的水质数据,采用主成分分析−多元线性回归模型等方法,研究其有机物、营养盐和重金属等的污染特征和入海通量,并分析其可能来源。结果表明,水质超标指标主要是高锰酸盐指数（COD_Mn）、氨氮（AN）浓度、总磷（TP）浓度和总氮（TN）浓度,其他指标符合I类地表水水质标准。TN/TP比值较高,严重偏离Redfield比值,陆源高含量氮和低含量磷的输入是造成渤海海水TN/TP升高的主要因素。非汛期的溶解氧（DO）浓度、电导率（EC）、AN浓度和TN浓度显著高于汛期,而非汛期的pH、浊度、COD_Mn和TP浓度显著低于汛期。2021年河口有机物和营养盐浓度受河流穿行农业区等因素的影响,重金属浓度则与域内工业企业分布有关。TN、TP、化学需氧量（COD）、AN和石油类年入海通量分别为3.63 × 10⁴ t、1 608.5 t、14.8 ×10⁴ t、3 086.6 t和221.9 t,Hg、Cd、Pb、As和Cr⁶⁺分别为0.264 t、0.253 t、1.978 t、20.434 t和31.651 t。研究区主要的污染源按照其贡献大小依次为生活污水和工业废水、水动力条件等水文因素所致的污染源、水−气界面物质交换及二次转化源和农田地表径流与交通运输产生的非点源。     

胶州湾高分辨率三维风暴潮漫滩数值模拟

基于海表气压项改进的FVCOM(Finite-Volume Coastal Ocean Model)海洋模式,研发胶州湾高分辨率三维风暴潮漫滩数值模式(JS-FVCOM).利用 JS-FVCOM 模式通过对天文潮、台风强度和径流3要素的不同组合,共设计了5个试验,分别进行风暴潮漫滩模拟实验.分析各试验结果得到如下结论:(1)随着台风最大风速的增加,风暴潮增水迅速增加,当综合水位超过防潮堤高程后增水速度明显减慢.海水淹没范围和淹没深度受综合水位超防潮堤高程时间影响明显.(2)在入海河流的河口区,当洪水位与高潮位相遇时,由于高潮位的顶托作用,洪水下泄不畅,造成综合水位上升明显,极易发生海水漫溢现象.JS-FVCOM 的模拟结果清楚地再现了海水漫堤的淹没过程,可为紧急情况下的人员疏散提供科学的基础数据.     

Green water overtopping analyzed with a SPH model

Wave overtopping on the decks of offshore platforms and ships can cause severe damage due to the high forces generated by the water. This phenomenon is analyzed within the framework of the Smoothed Particle Hydrodynamics (SPH) method. The presence of a fixed horizontal deck above the mean water level modifies strongly the wave kinematics. In particular, the flow in the wave crest is split into two, showing a different behavior above and below the deck. Numerical results generated by the SPH method are compared to laboratory experiments. The formation of a jet in the rear of the deck after overtopping is observed under extreme conditions.