流速逆变张量隐式求解方法及其在航道港池流场计算中的应用

运用高分辨率的边界适应网格进行流体动力学数值计算时,如何提高计算稳定性和减少计算量成为数值求解的关键性问题.在非正交的边界适应坐标系中,每个动量方程中同时出现了两个交叉方向的水位偏导数项,给隐式求解带来困难,而显式格式下的时间步长由于受与空间步长有关的Courant-Friedrichs-Lewy条件限制,计算量成倍增加.本文从广义曲线坐标系下浅海动力学方程组出发,导出了流速的逆变张量所满足的动量方程组,使方程中的水位偏导数项变成了沿某一协变基向量方向占优的形式,方便地采用了交替方向隐式差分格式,从而提高了计算稳定性并减小了计算量.本文通过对澳门海域航道和港池中流场的计算,证实了该模式是一种进行高分辩率数值计算的有效方法.     

An efficient mode-splitting method for a curvilinear nearshore circulation model

A mode-splitting method is applied to the quasi-3D nearshore circulation equations in generalized curvilinear coordinates. The gravity wave mode and the vorticity wave mode of the equations are derived using the two-step projection method. Using an implicit algorithm for the gravity mode and an explicit algorithm for the vorticity mode, we combine the two modes to derive a mixed difference–differential equation with respect to surface elevation. McKee et al.'s [McKee, S., Wall, D.P., and Wilson, S.K., 1996. An alternating direction implicit scheme for parabolic equations with mixed derivative and convective terms. J. Comput. Phys., 126, 64–76.] ADI scheme is then used to solve the parabolic-type equation in dealing with the mixed derivative and convective terms from the curvilinear coordinate transformation. Good convergence rates are found in two typical cases which represent respectively the motions dominated by the gravity mode and the vorticity mode. Time step limitations imposed by the vorticity convective Courant number in vorticity-mode-dominant cases are discussed. Model efficiency and accuracy are verified in model application to tidal current simulations in San Francisco Bight.     

无结构网格二维河口海岸水动力数值模式的建立及其应用

为完全拟合河口近海复杂岸线和工程结构以及有效局部加密,设计并建立了一个无结构三角形网格二维河口海岸水动力数值模式。空间离散主要基于有限体积法以保证守恒性,时间积分采用预估修正法以提高精度。水位在三角形网格中心通过连续方程求解;水平x方向和y方向的流速U和V均在网格边中点上通过动量方程求解。流速平流项的求解中采用了TVD格式。TVD流速平流通量为一个一阶迎风格式通量和一个二阶格式通量的组合,一阶格式通量和二阶格式通量根据流速的局部分布情况得出配比,最终组合得到TVD通量。TVD格式具有低耗散和无频散的优点,提高了模式的稳定性。应用实测资料验证建立的模式,结果显示水位、流速和流向的计算值与实测值均符合良好。     

基于速度-深度线性模型的时深转换方法及其在南海海盆深水区的应用*

介绍了沉积层速度-深度线性模型的原理及其基本特点,利用沿南海海盆深水区一条多道地震剖面解释的速度谱资料,将沉积层速度-深度线性模型应用于该剖面解释数据的时深转换中,建立了与之相关的一整套工作流程,整个流程实现了可视化,并考虑了沉积地层速度的横向变化,为地震剖面的地质解释提供了直观且更为可靠的素材。最后,分别从理论和实践角度分析探讨了该时深转换模型的应用前景和局限性,借此为后续研究工作提供参考。     

The FUNWAVE model application and its validation using laboratory data

In this paper, the performance of a well known and widespread Boussinesq model is evaluated for its ability to predict deep waters and shoaling zone velocity and elevation, comparing them with laboratory data. The model evaluation places emphasis on the parameters of the wave field that could be used for the prediction of coastal phenomena. It was found that the model proved its ability to predict regular wave velocity and elevation both in deep waters and shoaling zones right up to the breaking region. In contrast to previous works found in literature, the comparisons in this case are not limited to modelled and measured wave elevations, but also involve horizontal velocities. As a result, experimental and computed time series of wave elevations and horizontal velocities and their corresponding phase-averaged values are investigated along the wave channel, showing a good performance of the model.     

Numerical analysis of water exit for a sphere with constant velocity using the lattice Boltzmann method

In this paper, the three-dimensional water exit of a sphere with different vertical velocities is investigated numerically using the lattice Boltzmann method (LBM). In this method, the liquid-gas two-phase flow is simplified as a single-phase free surface flow. To capture the free surface, a mass tracking algorithm is incorporated into the LBM. The gravity as a body force is introduced in the form of calculating the equilibrium distribution with an altered velocity, while the surface tension is neglected. Besides, the employed bounce-back boundary conditions are used for a moving sphere. What’s more, the Wall-Adapting Local Eddy (WALE) viscosity model is employed to capture the turbulent structures of the flow and stabilize the simulation. The accuracy of the numerical results is demonstrated through comparisons with the previous numerical and experimental results in the literature. The results show that the spike height is significantly influenced under the Froude number (Fr) below 4.12 and slightly affected under the Fr varying from 4.12 to 8.24. After the sphere exits water totally, the evolution of the free surface waterfall can be described as two phases and becomes more intense with the Froude number increasing. The non-uniform distribution of velocity results in the breaking of the free surface after the sphere completely exits the water. Moreover, the Reynolds number greatly affects the wake dynamics and hydrodynamics acting on the sphere when it moves beneath the water surface.     

南沙海区珊瑚礁灰岩纵波波速特征及其影响因素 *

珊瑚礁灰岩是孔隙结构复杂、密度变化较大的一类岩石, 但过去对珊瑚礁灰岩纵波波速与孔隙结构的关系及其影响因素研究不够深入。本文测定和分析了南沙海区某岛礁钻孔中珊瑚礁灰岩的纵波波速、孔隙度以及密度特征, 结果显示礁灰岩的纵波波速变化范围为5104~5958m·s^-1, 孔隙度变化范围为1.47%~17.7%, 密度变化范围为2.07~ 2.72g·cm^-3。这些特征表明, 埋藏后的压实作用和重结晶作用, 对珊瑚礁灰岩的孔隙度和密度产生影响。珊瑚礁灰岩弹性波速主要受孔隙度和孔隙结构类型的影响, 礁灰岩横、纵波速比值能有效地确定岩体的结构和稳定性, 因此礁灰岩的声学特性研究成果可为珊瑚岛礁工程建设的稳定性评估提供可靠的数据支撑。     

冲绳海槽中部无井区速度场建立及应用

速度场的建立是冲绳海槽中部深入研究所必需的技术资料。作者选取冲绳海槽中部无井深水区二维地震数据, 以数据处理过程中的叠加速度数据为原始速度, 通过建立双层模型和异常速度识别剔除, 采用Dix 公式方法进行速度转换和沿层速度插值, 建立研究区速度场。从区域速度场问题建立宏观概念, 为冲绳海槽中部提供丰富可靠的速度资料, 变速成图得到的构造图件与地质认识相一致, 实现了由地震资料反映海底构造等地质信息的目的。     

基于构造-流体耦合约束的变速成图方法及其在东海A气田挖潜阶段的成功应用

时深转换是构造解释关键步骤之一,时深转换方法主要包括常速成图与变速成图两大类。常速成图操作简单,应用普遍,但不适合速度场横向变化剧烈的工区。建立一种适应速度场横向变化且符合工区地质及油气藏特征的时深转换方法,是本研究探讨的重点。迭代变速成图技术基于叠加速度反演,综合了流体检测成果,通过不断优化速度场开展变速成图,能较准确地预测地下复杂构造的深度,该方法刻画的构造油气藏含气范围与流体检测分布一致,实现了同一油气藏的分布在不同地震信息维度下的耦合。利用迭代变速成图技术,较好解决了A气田钻前构造气藏面积与“亮点”展布范围之间的矛盾,统一了地质油藏认识,扩大了地质储量,有效推动了A气田的挖潜与调整,实现了增储上产。     

Generation of random waves in time-dependent extended mild-slope equations using a source function method

We develop techniques of numerical wave generation in the time-dependent extended mild-slope equations of Suh et al. [1997. Time-dependent equations for wave propagation on rapidly varying topography. Coastal Engineering 32, 91–117] and Lee et al. [2003. Extended mild-slope equation for random waves. Coastal Engineering 48, 277–287] for random waves using a source function method. Numerical results for both regular and irregular waves in one and two horizontal dimensions show that the wave heights and the frequency spectra are properly reproduced. The waves that pass through the wave generation region do not cause any numerical disturbances, showing usefulness of the source function method in avoiding re-reflection problems at the offshore boundary.     

谱松弛动力降尺度方法及其在吕宋海峡黑潮模拟中的应用

本文采用区域高分辨率海洋数值模型,将谱松弛动力降尺度方法应用于吕宋海峡及其邻近区域,对吕宋海峡黑潮流径的流型特征进行模拟与分析。实验结果显示,应用谱松弛法能够较好地改善区域模型的模拟效果：通过约束大尺度误差,不仅能直接约束区域内的大尺度海洋状态,也间接调整了小尺度过程的演变规律,改善了吕宋海峡黑潮流径的模拟效果。     

二维赤潮生态数学模型及其在渤海的应用

采用ADI的有限差分方法对不可压缩流体二维浅水环流方程离散和求解,建立水动力数学模型,用迎风格式离散赤潮生物动力学方程,通过水动力学和生物动力学相结合的方法,建立了二维赤潮生态数学模型。将所建立的二维赤潮生态数学模型应用于渤海,针对渤海海域2004年6月11～16日发生的棕囊藻赤潮进行了数值计算。对EOS/MODIS卫星拍摄的2004年6月份的渤海海区卫星遥感图像进行了处理,提取出海水中的赤潮信息,并计算出赤潮面积,使其与模型计算出的赤潮面积进行对比验证,结果基本吻合,表明该模型能够较好地模拟赤潮的生消过程,为渤海地区的赤潮预报提供了科学依据。     

浙闽沿海和台湾海峡海域冬季大风风速计算方法探讨

本文利用东海区海陆大风对比试验结果及26艘船只两个月的海上航测实况资料，通过对各种风速进行海陆比值分析、差值分析和测站间对比分析。论证了据陆上大风推算该海区大风风速计算式的可靠性，从而为实时、定量地预报海区大风提供了1种方法．     

南海中建南盆地速度资料分析与应用

在大量速度谱解释的基础上,分别计算了南海中建南盆地的层速度、时深转换和砂岩百分含量,并对盆地5套地层的层速度平面图进行了分析。结果表明,中部坳陷的层速度最大,北部坳陷和南部坳陷次之,北部隆起的层速度最小,反映了地层的构造走势;利用砂岩百分含量资料进行岩性分析,发现西北部和西南部的砂岩百分含量大于75%,属于砂岩相沉积,推测盆地的物源主要来自西北和西南方向,为沉积相解释和油气资源评价提供了依据。     

A method to calculate design tide levels on the basis of numerical model of tidal current and its application

In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tidal current is proposed. The essentials of the method are described, and its application is illustrated with an example. The results of the application show that the design tide levels calculated by the method are close to those determined by long-time measured tide level data, and its calculation precision is high, so it is feasible to use the method to determine the design tide levels in the areas.     

An experimental method to identify a component of wave orbital motion in propeller effective inflow velocity and its effects on load fluctuations of a ship main engine in waves

Improvements of estimation accuracy on propeller torque fluctuations in waves will contribute assessments on safe operation of a ship main engine as in adverse sea condition. The propeller torque and thrust in waves can be estimated by propeller effective inflow velocity in waves, using the propeller open-water characteristics. Fluctuation components in the mathematical model of the propeller effective inflow velocity in waves can be composed of two components, respectively caused by ship surge motion and wave orbital motion at propeller position. In this study, an experimental method by the model test to directly identify the characteristics of the component by the wave orbital motion is newly proposed. Furthermore, the free-running model test in regular waves, using a simulator of the marine diesel engine which manages the shaft speed of the motor on a ship model as behaving the actual diesel engine, is carried out to obtain realistic torque fluctuations for comparisons of the estimated results applying the proposed identification method. Through comparisons of estimated fluctuations with the measured results, the proposed approach for the component of the inflow velocity due to wave orbital motion is successfully validated.     

湛江毗邻海域流场模型在海上搜救中的应用

依据<海岸与河口潮流泥沙模拟技术规范>建立湛江毗邻海域二维流场模型方程组[模拟区是(105°38'E、15°56'N)、(105°38'E、22°14'N)、(113°24'E、22°14'N)、(113°24'E、15°56'N)四点连线范围];采用"等步长"差分网格分割方法和ADI方法数值离散方程组,在确定了边界条件和初始值后,用追赶法求解.模拟出本研究海区的3种流场:一是潮流场;二是考虑了定常风作用后的流场;三是海上遇险目标漂流场.结果为该海域遇险目标搜寻与救助提供了技术支持.     

Study on short-range numerical forecasting of ocean current in the East China Sea-Ⅲ Three-dimensional baroclinic anomaly forecasting model and its application

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赤潮高发期间厦门海域叶绿素值预报方程建立及应用于灾害性赤潮预报模式的研究

利用厦门海域2005—2008年海洋水质自动连续监测仪器的多年全天24 h连续监测所获取的海水各项因子的有关数据,对其进行24 h滑动平均处理后,再进一步筛选整理形成统计所需样本,采用逐步回归统计方法建立28 h预报方程,试图能对和赤潮产生有紧密关系的叶绿素含量变化做出短期预报,并尝试将预报结果应用于灾害性赤潮预报业务。     

台湾海峡及其西边地区正常地震动态及危险性特征

本文从地震的时，空分布特征，区域应力场动态，能量释放方式，ｂ值及震群特征６个方面研究了台湾海峡及其西边地区地震活动的正常动态及异常特征。结果表明，具有前兆意义的变化模式表现为区域地震活动在时间，空间及功能方面的有序性变化，即：（ａ）地震空间分布由分散转为集中，形成条带或空区；（ｂ）断裂活动由多组转为单一，应力场趋向一致；（display status