SPH法模拟立面二维溃坝流动应用研究

光滑离子流体动力学(SPH)法是一种纯拉格朗日(Lagrange)无网格方法,近年来发展日趋成熟。对SPH法的基本原理、核函数及控制方程离散格式、边界处理方法等进行了介绍。在此基础上建立了数值水槽模型,模拟了立面二维溃坝流动问题,并将所得结果与VOF法及模型试验得到的结果进行比较,结果表明:SPH法能够捕捉到流体的飞溅及融合现象,适于模拟具有瞬时极大变形等物理力学问题。     

无网格方法在二维弹性力学计算中的应用

通过选取合适的权函数和基函数，将无网格局部伽辽金法用于二维弹性力学计算．计算中，积分都在规则形状边界子域上完成，因而容易实现；通过罚因子添加本质边界条件，从而使得到的刚度矩阵是正定对称矩阵．将计算结果与ANSYS有限元法的计算结果进行比较，结果表明，无网格法用于二维弹性力学计算具有精度高、稳定性好和适应性强等优点．     

电磁波在光子晶体中介质界面的传输矩阵

为探讨电磁波在光子晶体中两介质界面的传播特点,利用电磁场的边界条件,导出了电磁波在介质交界面传播的传输矩阵,并用此矩阵讨论了透射波和反射波的相位和偏振特征;得到了反射波相位发生突变的条件和布儒斯特定律。     

FEM-BEM Coupling for the Modelling of Induction Heating Processes Including Moving Parts

IntroductiollAnyelectricalconductorplacedinatime-varyingmagneticfieldistheseatofeddycurrentsthatdissipatepowerthroughJouleeffect.ThispowerisconcentratedinthesurfaceofthecomPonent,inaverysmallthicknesswhichdependsontheelectricalconductivityandmagneticpermeabilityofthematerial,butalsoonthefrequencyofthecurrents.Inductionhardeningprocessestakeadvantageofthiseffectbecauseitthereforepossibletocontrolthethicknessofthetreatedlayer.InductionhardeningofsteelcomPonentsisrealisedintwosteps.First,anindu…     

基于2D弹性理论的船舶板结构无网格技术

应用无网格局部Petrov-Galerkin法对船舶平直板结构进行了研究。运用最小二乘法和加权余量法来求解结构位移场量的逼近函数,给出了问题的控制方程和刚度方程。通过算例与有限元法计算结果进行了比较分析,验证了文章提出方法的正确性。文章研究对于分析船舶结构变形和应力具有良好的适用性。     

Nonlinear Dynamic Analysis of Three Dimensional Flexible Multibody Systems

The nonlinear dynamic problems of three dimensional flexible multibody systems are investigated. The elastic deformation fields of flexible space beams are decomposed into axial deformation and bending deformation, and described by each exact vibration modes in the body coordinate systems. The constrainted nonlinear dynamic equations are derived by using Lagrange multiplier method. A numerical procedure for solving the resulting differential algebraic equations is presented based on Newmark direct integration method combined with the modified Newton-Raphson iterative method. Numerical results verify the effectiveness of the proposed method.     

基于增强拉格朗日乘子法的容量制约交通分配问题研究(英文)

传统的交通分配问题(TAP)没有容量的限制,但是事实上,路段和网络都有其自身的容量限制。传统的用户均衡网络模型允许分配的交通流量结果超过其容量,这显然是不合理的。首先,介绍了起点算法的基本原理及其有效的实现,并运用一个算例网络进行交通分配;然后,运用增强拉格朗日乘子法针对具有容量限制的该网络重新进行交通分配,并将两种结果进行比较。实验结果表明:增强拉格朗日乘子法具有良好的运算性能和效率,并且更具有实际意义,能够更加合理的运用到实际的交通分配问题中。     

停车需求分布的双层规划模型及算法

针对停车需求给定条件下的停车设施选择问题,建立了描述停车设施选择和出行路线选择行为的双层规划模型,并基于在部分增广乘子法中嵌套Frank-Wolfe算法的思路设计了求解模型的有效算法.上层模型在满足停车需求和设施停放车辆数有限条件下,力图最小化实际停车需求分布与期望分布间的差异.下层模型假设出行者路线选择行为遵循用户均衡原则.上下层模型通过设施选择概率函数实现有效关联.部分增广乘子法中嵌套Frank-Wolfe 算法求解上层模型可以有效利用上层模型的单纯形式约束特征.算例分析验证了新模型与算法的有效性.研究结论拓展了现有理论的应用场景,为相关研究提供了新的建模分析思路.     

Reproducing Kernel Particle Method for Non-Linear Fracture Analysis

To study the non-linear fracture, a non-linear constitutive model for piezoelectric ceramics was proposed, in which the polarization switching and saturation were taken into account. Based on the model, the non-linear fracture analysis was implemented using reproducing kernel particle method （RKPM）. Using local J-integral as a fracture criterion, a relation curve of fracture loads against electric fields was obtained. Qualitatively, the curve is in agreement with the experimental observations reported in literature. The reproducing equation, the shape function of RKPM, and the transformation method to impose essential boundary conditions for meshless methods were also introduced. The computation was implemented using object-oriented programming method.     

无网格对称粒子法中两类热边界条件的处理

第二、三类边界条件对无网格对称粒子法求解瞬态热传导问题的计算精度和稳定性有重要影响。提出一种有效的方法来处理这两类边界条件。该方法采用统一表达式描述两类边界条件,并将边界粒子分为光滑域内的边界粒子和非光滑域的边界粒子。对于前者,在温度导数的对称粒子近似中引入边界条件方程,精确地施加边界条件;对于后者,根据其相邻粒子的温度导数,采用具有一阶连续性的粒子近似,计算出其温度导数。应用该方法计算了一个数值算例。计算结果与解析解和有限元法的计算结果符合良好,且计算误差随时间呈下降趋势,说明该方法具有良好的精度和稳定性。     

磁电弹性材料断裂力学研究现状

磁电弹性材料断裂问题已成为力学研究工作者的研究热点。全面回顾了近年来磁电弹性材料断裂力学的研究现状,主要讨论了：反平面裂纹问题、平面裂纹问题、硬币型裂纹问题以及有限元、边界元和无网格法在磁电弹性材料断裂问题中的应用。     

杂交边界点法在沥青路面裂纹分析中的应用

杂交边界点法在积分和插值时都不需要网格,它是将移动最小二乘近似与修正位移变分原理结合起来,不但不需要划分网格,而且具有边界点法降维和高精度的优点。应用杂交边界点法对沥青路面表面裂纹扩展中强度应力因子变化规律和裂纹扩展路径进行研究,并对面层、基层设计参数对裂纹扩展影响规律进行分析,探讨沥青路面的裂纹扩展机理,具有一定的工程实用价值。     

Application of method of fundamental solutions in solving potential flow problems for ship motion prediction

A novel panel-free approach based on the method of fundamental solutions (MFS) is proposed to solve the potential flow for predicting ship motion responses in the frequency domain according to strip theory. Compared with the conventional boundary element method (BEM), MFS is a desingularized, panel-free and integration-free approach. As a result, it is mathematically simple and easy for programming. The velocity potential is described by radial basis function (RBF) approximations and any degree of continuity of the velocity potential gradient can be obtained. Desingularization is achieved through collating singularities on a pseudo boundary outside the real fluid domain. Practical implementation and numerical characteristics of the MFS for solving the potential flow problem concerning ship hydrodynamics are elaborated through the computation of a 2D rectangular section. Then, the current method is further integrated with frequency domain strip theory to predict the heave and pitch responses of a containership and a very large crude carrier (VLCC) in regular head waves. The results of both ships agree well with the 3D frequency domain panel method and experimental data. Thus, the correctness and usefulness of the proposed approach are proved. We hope that this paper will serve as a motivation for other researchers to apply the MFS to various challenging problems in the field of ship hydrodynamics.     

320kA预焙铝电解槽电磁场分布计算与优化

利用ANSYS电磁场有限元法,建立了320 kA预焙铝电解槽三维电磁场有限元模型,计算了铝电解槽内的电场分布及磁场分布,计算结果与实测结果相吻合,验证了该模型的正确性.在此基础上提出了一种新型电解槽结构,并应用参数化设计语言（APDL）建立该结构的电磁场计算模型,以磁场为目标对该结构进行了整体优化.最终优化后电磁场分布表明：该结构铝电解槽能减小铝液层水平电流,磁场分布对称性好,有利于改善槽内铝液的流动状态,具备较大的节能潜力.     

竞争环境下航班舱位控制博弈模型

分析了中国航空市场的特点,以定义不同票价等级下各航空公司所提供的座位数为决策变量,舱位容量为约束条件,各家航空公司收益最大化为多目标函数,构建竞争环境下中国航空公司舱位控制的博弈模型,利用拉格朗日乘数法求解各航空公司最优低价票数,并以此来确定均衡舱位.仿真试验表明:各家航空公司舱位控制策略相互制约且能够达到均衡状态,但受到旅客需求随机性的影响,在12 000次的仿真试验中达到均衡的概率为12.68%,达不到均衡的概率为87.32%,因此,这种均衡是动态的且实现机率较低,结论与实际相符,模型切实可行.     

板梁偏心连接结构有限元分析

为了合理处理列车车体结构分析中典型的板梁偏心连接问题,分别基于罚单元法和La-grange乘子法构造了板梁组合结构模型,将组合结构中相关节点对之间通过偏心关系建立的约束方程引入到平衡方程中,解决了梁单元因偏心连接而对组合结构总体刚度矩阵的贡献问题,并编制了求解板梁组合结构静强度计算问题的有限元程序。实例计算表明不但两种计算方法的计算结果吻合,而且其计算结果均与有限元分析软件ANSYS 9.0计算结果接近,位移误差在1%以内,应力误差在2%以内,分析表明二者均是处理板梁偏心连接组合结构的有效方法。     

面向车联网的高速路OD矩阵估计模型

针对高速路OD矩阵的采集与估计,提出采用RFID技术的车联网进行部署,建立有缺失数据的OD矩阵采集方法.用拉格朗日乘数法求解OD矩阵元素概率的极大似然估计,给出基于EM算法的OD矩阵估计算法.通过912节点规模的仿真实验结果表明,提出的算法相比模拟采集准确性更高,真实数据的均方根误差降低了77.7%,验证了算法流程和模型的有效性.      

分层海洋环境对潜艇腐蚀相关静态电磁信号的影响研究

来源于腐蚀及防腐电流的静态电、磁信号是潜艇水下新的重要的目标特性.为掌握分层海洋环境对其水下分布特征的影响,采用三层平行分层导电媒质模型模拟海洋环境、水平直流电偶极子模拟潜艇腐蚀相关电磁场源,通过数值仿真,研究环境电导率、海洋水深、分层界面等因素对潜艇腐蚀相关静态电场和静态磁场的影响.仿真分析结果表明,分层海洋环境对场有明显影响,且存在普通规律.     

Penalty-Finite Element Analysis of the Eddy Current Loss in a Fully-Stabilized Multifilamentary Superconducting Wire

The paper is mainly concerned with the penalty incurred in finiteelement analysis of the eddy-current loss problem in a fully established multi-filamentary superconducting wire. A finite element model with 4-node quadrilateral isoparametric elements is formulated for the present problem. Unlike the conventional vector potential scheme in use for electromagnetic field problem, the present work features a direct computational approach to eddy current loss. Simplicity and remarkable enhancement in computational accuracy can be obtained with the proposed method.     

A Method to Improve First Order Approximation of Smoothed Particle Hydrodynamics

Smoothed particle hydrodynamics (SPH) is a useful meshless method. The first and second ordersare the most popular derivatives of the field function in the mechanical governing equations. New methodswere proposed to improve accuracy of SPH approximation by the lemma proved. The lemma describes therelationship of functions and their SPH approximation. Finally, the error comparison of SPH method with orwithout our improvement was carried out.