垂向二维悬沙输移有限元数学模型

采用四节点任意四边形等参单元,根据G a lerk in有限元法进行数值离散,建立了潮汐河口沿宽度积分平均的垂向二维泥沙数学模型。模型中,对扩散项通过分步积分和G reen公式变换,精确满足了自由表面和底床边界条件;经采用有解析解的算例对模型进行验证,计算值和理论解相吻合。     

明渠交汇口水流浅水二维数学模型研究

针对明渠交汇口缓流流动特性,建立基于高性能有限体积数值方法、具有二阶精度的非恒定浅水二维水流数学模型。基本控制方程采用浅水二维水流方程;采用能够有效捕捉激波的高性能有限体积方法离散控制方程;采用了隐式方法处理阻力项,从而保证了模型的稳定性。采用非结构三角形网格系离散计算区域。最后,应用实测资料对两种模型进行了验证比较,结果表明该模型可模拟明渠交汇口基本流动特性,显示了对天然河流广阔的应用前景。     

电厂贮灰坝的渗流数值分析

建立了饱和—非饱和渗流模型,采用空间有限元离散、隐式时间差分方法求解描述饱和—非饱和渗流场非线性抛物型方程,提出了计算电厂贮灰坝渗流的数值计算方法。将辽源发电厂贮灰坝进行二维渗流数值计算,计算结果与水电模拟实验结果进行比较,表明结果是可靠的。     

网格节点型有限体积法在滑动轴承润滑特性求解中的应用

本文采用网格节点型有限体积法求解二维瞬态雷诺方程,采用矢量化方法离散雷诺方程,从而构建并得到新的数值模型,该模型既有有限体积法守恒性的特点,又能适用于结构复杂的求解域.通过与相关算例的对比验证,证明了该模型可适用于滑动轴承润滑特性的研究,同时精度也可以得到保证;根据计算得到的压力分布特点,采用不同的网格类型和网格数量重新划分求解域,并对计算结果和时间进行了对比,结果表明可以采用不同的稀疏网格来提高计算效率;通过计算圆锥形织构轴承的压力分布,证实了该模型对复杂求解域的良好适用性.     

网格节点型有限体积法在滑动轴承润滑特性求解中的应用（英文）

本文采用网格节点型有限体积法求解二维瞬态雷诺方程,采用矢量化方法离散雷诺方程,从而构建并得到新的数值模型,该模型既有有限体积法守恒性的特点,又能适用于结构复杂的求解域。通过与相关算例的对比验证,证明了该模型可适用于滑动轴承润滑特性的研究,同时精度也可以得到保证;根据计算得到的压力分布特点,采用不同的网格类型和网格数量重新划分求解域,并对计算结果和时间进行了对比,结果表明可以采用不同的稀疏网格来提高计算效率;通过计算圆锥形织构轴承的压力分布,证实了该模型对复杂求解域的良好适用性。     

二维有限元潮流数学模型及其应用

采用有限元Galerkin加权余量法对二维潮流控制方程进行求解,建立了二维有限元潮流数学模型,并将模型运用于计算区域较小、边界较为复杂的海安湾。对海安湾潮流数值模拟的结果如下:计算水位和流速的大小及过程均与实测情况极为吻合,流场的趋势也与以往研究较为一致。新模型能采用不同形式的非结构网格,对于边界和地形变化复杂的工程区域有较强的适应性。研究成果说明,对于计算区域较小且陆域边界变化复杂的工程问题,采用有限元方法离散潮流方程能提高计算精度。     

基于BFC-VOF方法的弧形防浪墙水动力数值模拟

文章建立了一种基于适体坐标系(BFC)的计算流体力学模型.采用坐标变换方法实现了任意复杂区域的结构化网格划分,在贴体网格下对二维不可压缩粘性流体的控制方程进行了离散,修正了贴体坐标下的界面跟踪方法(VOF方法).对弧形防浪墙结构附近的压力场,波面历时曲线进行了数值计算.将采用适体坐标的计算结果与在笛卡尔坐标网格下采用部...     

砂井地基堆载沉降的PFC2D模拟

砂井是利用土的排水固结原理来处理软弱地基的代表性施工技术。针对现有的软基沉降计算和预测方法存在的不足,利用离散单元法中二维颗粒元法PFC2D建立了砂井二维模型,对砂井地基堆载沉降过程进行二维离散元仿真模拟。采用由2～7个不同组合方式的簇单元来体现软基的孔隙率,改进了PFC2D中的水位降深模型,分析了软基沉降过程中水位的变化规律。模拟与现场实测结果的对比表明:模拟沉降值与实测值基本吻合。     

冰区船舶碎冰载荷模拟及影响参数分析

本文采用二维离散元法模拟碎冰与船舶的相互作用.运用海冰粘弹性的Kelvin模型,结合船舶与碎冰的耦合运动,通过Newmark法求解三自由度船舶运动方程,计算船舶航行于碎冰区的碎冰载荷.与相关文献进行对比,验证本文数值模型的可行性.研究海冰不同的弹簧系数、粘性阻尼系数与摩擦系数对碎冰载荷的影响.结果表明:二维离散元数值模...     

高速船垂向振动流固耦合分析

本文建立了一种二维实用模型,结构部分采用二维有限元法计算,流体部分采用考虑两种不同边界条件（线性自由表面条件和采用高频极限近似自由表面条件）的二维边界方法计算,应用改进的行列式搜索法以及交叉迭代法求解特征值及对应的特征向量,解决流固耦合问题。通过采用不同的附加质量计算方法及以不同的模型（杆－膜或梁－膜模型）分别进行计算,并对结果进行了比较分析。实船计算表明,本文所编制的程序计算结果可靠,具有较强的     

导弹分段刚体模型和弹性体模型的动响应区别

针对目前一种新提出来的潜射导弹分段刚体模型的试验方案,通过求解在同一载荷作用下分段刚体模型与实际弹性体模型的动响应,来定量分析该模型试验所测得极大载荷值和实际情况下极大载荷的偏差.     

基于模型的耙吸挖泥船溢流损失估计及模型验证

对大型耙吸式挖泥船的装舱作业过程做了充分研究,重点解决了泥舱模型的溢流损失估计问题。利用多组实测数据,对3种泥舱沉积模型的估计效果进行了数据验证和评估分析,给出最终的评估结果。这一理论成果将应用于以后的挖泥船辅助决策和自动控制应用中。     

Use of 3D compartment model for simplified full ship FE model. Part I: construction of FE model

Classification societies cannot cover the torsional strength assessment with simple empirical formula as the size of a containership increases drastically over 10 000 TEU in recent years. Torsional strength of a container ship is very difficult to estimate with an analytical method due to its alternatively varying cross sections, i. e. an open and a closed section. This article proposes an approach to construct a simplified FE model using a 3D compartment model available from the beginning of ship design process. The model is cut to pieces of lots of small pieces of lines by a set of transverse, longitudinal and horizontal planes. Two algorithms are developed for mesh generation of internal structures; one for assembling the broken lines into closed loops and the other for automatically generating mesh from the loops. Another algorithm is proposed to generate mesh for outer hull using outermost nodes of the FE model built for internal members. The validity of the simplified model is discussed along with a beam theory based approach in J Mar Sci Technol (2008)     

Error correction of a predictive ocean wave model using local model approximation

Constructing models from time series with nontrivial dynamics is a difficult problem. The classical approach is to build a model from first principles and use it to forecast on the basis of the initial conditions. Unfortunately, this is not always possible. For example, in fluid dynamics, a perfect model in the form of the Navier–Stokes equations exists, but initial conditions and accurate forcing terms are difficult to obtain. In other cases, a good model may not exist. In either case, alternative approaches should be examined. This paper describes an alternative approach of combining observations and numerical model results in order to produce an accurate forecast. The approach is based on application of a method inspired by chaos theory for building nonlinear models from data called Local Models. Embedding theorem based on the time lagged embedded vectors is the basis for the local model. This technique is used for analysis and updating of numerical model output variables to forecast and correct the errors created by numerical model. The local model approximation is a powerful tool in the forecasting of chaotic time series and has been employed for wave prediction in a forecasting horizon from a few hours to 24 h. The efficacy of the local model as an error correction tool (by combining the model predictions with the observations) compared with the predictions of linear auto regressive models has been brought up. In the present study, the parameters driving the local model are optimized using evolutionary algorithms.     

指数平滑模型探讨

指数平滑模型在经济预测中应用较为广泛,时间序列的变动趋势不同,应用的平滑模型有所区别。本文介绍了各种指数平滑模型,并以某港为例分别用三次指数平滑及二阶差分—指数平滑模型对其吞吐量进行了预测,并做出了各种模型的适用性分析。     

电信计费模型的设计

依据电信计费系统存在的问题,本文详细描述了电信计费模型的设计方法和各个模块的设计内容。     

多模型估计理论

研究利用多模型来副近系统的动态性能,基于多模型设计组合导航系统的多模型自适应卡尔曼滤波器.通过仿真研究表明,在多模型自适应估计和交互式多模型滤波均克服了单一滤波由于外部扰动所造成的滤波误差过大甚至发散的问题.多模卡尔曼滤波器对组合导航系统能达到理想的控制精度、跟踪速度以及稳定性.研究表明,运用多模卡尔曼滤波能改善系统的瞬态响应,覆盖大范围的参数不确定性.     

Validation of vessel seakeeping model tuning algorithm based on measurements at model scale

Wave-induced vessel motion prediction plays a critical role in ensuring safe marine operations. The operational limiting criteria can usually be calculated by applying presumed linearized vessel motion transfer functions based on the specified vessel loading condition, which may deviate from the real vessel condition when the operation is executed. Reducing the uncertainties of the onboard vessel loading condition can therefore improve the accuracy of vessel motion prediction and hence improve the safety and cost-efficiency for marine operations. However, parameters related to the onboard vessel loading condition can be difficult to measure directly, such as the center of gravity and moments of inertia. In addition, the hydrodynamic viscous damping terms are always subject to significant uncertainties and sometimes become critical for accurate vessel motion predictions. A very promising algorithm for the tuning of these important uncertain vessel parameters based on the unscented Kalman filter (UKF) that uses onboard vessel motion measurements and synchronous wave information was proposed and demonstrated previously by application to synthetic data. The present paper validates the UKF-based vessel seakeeping model tuning algorithm by considering measurements from model-scale seakeeping tests. Validation analyses demonstrate rational tuning results. The observed random errors and bias in relation to the measurement functions due to the applied simplification and linearization in the seakeeping simulations can lead to biased tuning. The importance of designing the state space and the measurement space is demonstrated by case studies. Due to the nonlinear relationship between the uncertain vessel parameters and the vessel motions, the tuning is shown to be sensitive to the mean state vector and selection of the surrounding sigma points.     

Use of a 3D compartment model for simplified full ship FE model. Part II: validation of the simplified FE model

This is Part II in a series of papers. Part I (J Mar Sci Technol 13:154–163) deals with an approach employed to construct a simplified FE model using a 3D compartment model available from the beginning of the ship design process. This paper begins by describing the limitations of an analytical approach based on shear warping beam theory for assessing torsional strength. Next, the structural parts of a container ship that have a negligible effect on hull girder bending strength and torsional strength are determined. This is verified by removing these parts from a conventional FE model and comparing the results obtained using this modified model with those yielded by the original model. The fore end part, the aft end part and the deck house are examined. Since these parts have complicated structures and relevant drawings for them are issued later than cargo structure drawings, modeling them exactly can result in a delay in the completion of the full ship FE model. This paper also verifies the validity of the simplified FE model built by applying the method proposed in Part I and comparing the results obtained with it with those given by a conventional full ship FE model. The stresses on hatch coaming top, the maximum diagonal elongations of the hatch coaming, and the maximum hatch corner movements are evaluated to check the validity of the simplified model.     

港口锚地选址海域适用性评价及优化模型

合理的锚地选址可以保障船舶锚泊安全性,同时可以优化港口的平面布置,提高港口运营效率。总结解决锚地选址问题的现有方法,分析GIS技术在选址问题中的运用,明确锚地选址影响因素并建立综合评价指标体系,同时确定各指标权重值,通过海域适用性评价模型对所有栅格进行综合评价。基于海洋功能区划等约束条件,获得锚地选址的可行方案集,优化比选出最优方案。通过算例分析,验证本文提出的模型合理、可行,可作为锚地选址优化的一种方法。