表面棱边单元法求解三维电磁场问题

提出了表面棱边单元方法并应用它求解任意形状物体的三维电磁场散色问题.首先根据物体剖分得出表面区域的几何特性,推导出表面棱边单元法的基本公式.该方法保持了普通棱边单元法的基本特性,维持变量的切向分量连续.然后用复合积分方程来模拟普通介质的电磁场散色问题,应用所提出的方法离散积分方程,并且对奇点问题采用特殊的处理方法.最后用该方法计算圆柱体以及四方体的在不同介质条件下的电磁场散色问题,对所得的数值解进行测试,并与其他数值方法解相比较,结果表明该方法行之有效.     

导体面目标电磁散射特性分析的无网格方法研究

将无网格迦辽金法推广应用于导体面目标电磁散射与辐射问题的研究.由移动最小二乘近似原理来拟合表面电流函数,基于电磁场积分方程,利用加权残量法导出导体面目标电磁散射场计算的离散模型,避免了传统的基于网格抛分的数值方法的瓶颈问题.为了验证所述的模型和算法,给出了导体方板电磁散射特性的计算实例.     

流体力学边界元算法

本文介绍了用边界单元法求解粘性流体力学问题中的Navier-Stokes方程和能量方程的基本思想和求解技术,给出了二、三维问题的基本解,利用连续性方程导出了计算压强以及温度的积分方程.本文所述方法的特点是表述方程的未知量是流体力学问题的基本物理量,即流速、压强和温度.对于不可压缩流体,压强和温度的计算公式与流速的计算公式是非耦合的,因而可以当流速求出后独立计算,从而能提高计算效率.此外,流速的梯度计算公式可以解析地从流速的积分方程中导出,因而流速梯度具有与流速本身同样的精度,这是其它方法如有限单元法、有限体积法所不能达到的.     

基于矩量法的三维介质目标电磁散射特性研究

想要具体地分析三维介质目标的电磁散射问题,需要知道未知电磁流系数.首先介绍三维介质目标的体积分方程,接着将体积分方程变为矩阵方程,在此过程中利用了矩量法进行了转化,根据矩阵方程对电磁流系数进行了计算,从而得出三维介质目标的雷达散射截面,最后对具体的三维介质目标：介质球、介质立方体的RCS进行了计算.实验结果表明：基于矩量法的三维介质目标的电磁散射特性分析是准确有效的.     

用有限元仿真法研究电机沟槽内磁场分布

采用ANSYS有限元分析软件对电机沟槽内磁场进行有限元分析,在三维磁场分析中,当存在非均匀介质时,针对理论上用基于节点的连续矢量位进行有限元计算所得的解为不精确解,采用棱边单元法来消除这些理论上所存在的缺陷。在建立有限元模型并加载边界条件和载荷后,进行仿真计算,求出电机沟槽分别在确定电流、交流电流激励作用下的磁场、储能、焦耳热损耗和受力等,使电机沟槽内磁场分布的计算变得精确高效。     

壳梁组合结构自由阻尼处理有限元分析

构造了壳梁组合结构自由阻尼处理薄板结构的有限元模型, 将板单元的节点作为主节点, 梁单元的节点作为从属节点, 推导出相应的刚度矩阵和质量矩阵. 在用有限元法进行结构动态特性分析的基础上, 用模态变形能法估算了结构的模态损耗因子. 最后以一计算实例将本文方法所得结果与用ANSYS软件计算所得结果进行了比较, 结果表明本文方法计算效率高、简单可行, 且具有较高的精度和工程实用性.     

柱体三维电磁场的泊松方程的数值计算

用数值法中最常用的有限差分法计算柱体三维静电场的泊松方程,计算有限网格点上的函数值近似逼近连续区域内的真实解,在计算机的辅助下,计算出电磁场的数值解.     

MIDAS/Civil在预应力空心板简支梁桥结构抗震分析中的应用

以有限单元法基本理论为基础,介绍了有限元通用软件MIDAS/Civil在预应力空心板简支梁桥结构抗震计算中的应用问题.采用三维有限元法,实现了预应力空心板简支梁桥的动力特性模拟,分析了在E1、E2地震作用下,桥梁各控制截面的抗弯能力、抗剪能力,以及支座厚度和抗弯稳定性等抗震性能,并提出切实可行的抗震措施,为桥梁施工质量控制提供必要的理论指导与技术支持.     

固体电枢溶化波烧蚀的一维数值模拟

建立了一维固体电枢溶化波烧蚀计算模型,采用有限差分法计算电磁场的扩散,得到了溶化波烧蚀速度和烧蚀深度的变化特性。数值计算结果表明,暴露于强磁场环境下的烧蚀表面产生较高的磁场梯度,电流密度集中在烧蚀表面,焦耳热的剧增导致电枢发生烧蚀。将伪烧蚀算法应用于有限差分的计算,证实其不相容。计算结果对溶化波烧蚀问题的理论及试验研究有重要的指导作用。     

面板堆石坝流变特性研究

简要介绍了某水电站混凝土面板堆石坝工程概况和流变计算模型。采用三维有限单元法对该混凝土面板坝筑坝及蓄水过程进行模拟计算,对比考虑堆石料流变和不考虑流变的两种计算结果,分析说明筑坝材料的流变特性对面板坝坝体以及混凝土面板变形应力的影响。     

Surface motion of alluvial valley in layered half-space for incident plane P-waves

The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be solved by the direct stiffness method, and the scattering wave response is calculated by Green’s functions of distributed loads acting on inclined lines in a layered half-space. The method is verified by comparing its results with literature and numerical analyses are performed by taking the amplification of incident plane P-waves by an alluvial valley in one soil layer resting on bedrock as an example. The results show that there exist distinct differences between the wave amplification by an alluvial valley embedded in layered half-space and that in homogeneous half-space and there is interaction between the valley and the soil layer. The amplitudes are relatively large when incident frequencies are close to the soil layer’s resonant frequencies.     

表面磁钢永磁无刷电机电磁转矩的解析法分析

With the air gap magnetic field distribution of surface mounted permanent magnet （PM） motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis （FEA）. In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.     

表面磁钢永磁无刷电机电磁转矩的解析法分析

With the air gap magnetic field distribution of surface mounted permanent magnet (PM) motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis (FEA). In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.     

圆柱导体对强电磁脉冲的散射特性研究

利用数字信号处理技术和电磁场理论,研究了圆柱形导体目标对强电磁脉冲波的散射及目标表面上感应电流;仿真了目标对脉冲散射的同极化衰减随时间的变化以及目标上的脉冲电流的时间变化规律。这不仅适用于研究导体目标的脉冲散射特性,而且适用于形状复杂目标的脉冲散射特性研究介质中的脉冲衰减研究,具有算法简便、准确、高效等特点。     

Measurement of Rotatory Optics Element in Tensor Dielectric Matrix for Rotatory Optical Fiber

The rotatory optics element in the tensor dielectric coefficient matrix is an important parameter for analyzing and calculating a rotatory optical fiber by electromagnetic theory. But the measurement of rotatory optics element is difficult for the rotatory optical fiber. A simple principle and method for measuring rotatory optics element are put forward in this paper. Firstly by using electromagnetic theory it was demonstrated that the rotatory optics element has a simple linear relation with the rotatory angle, and then the rotatory optics element has a simple linear relation with the magnetic field strength (or bias current in the helix coil) . Secondly a measurement system for the rotatory optics element in the rotatory optical fiber was designed. Using the measurement system the rotatory element can be obtained by measuring the bias current simply.     

Dynamic stiffness for thin-walled structures by power series

INTRODUCTION Thin-walled structures have considerable tech-nological importance in many situations of engi-neering practice. The rotary and warping inertia terms should be considered in the analyses of thin-walled structures (Alwis and Wang, 1996), although it is difficult to obtain the analytical solutions of govern-ing differential equations, especially of thin-walled frame and spatial twisted structure. The finite element method (FEM) is widely used for vibration and sta-bility analy…     

分层各向异性有耗介质的反射和透射系数计算

在广义传播矩阵（CTM）方法分析各向异性分层介质传播特性的基础上，对数值计算进行了研究，克服了有耗介质计算时发散的困难，指出了编程计算时应该注意的问题。在半空间条件下，对分层各向异性有耗介质的反射和透射系数进行了计算，将GTM方法与精确解对比，计算结果一致。     

导体椭球面上电荷分布的尺度分析法

从电磁尺度变换关系出发,考虑了由于尺度伸缩所引起的空间电磁特性的变化,得到了导体椭球上的电荷分布表达式,在椭球的三个半轴相等时,该表达式退回到导体球上的电荷分布;将所得结果与有关文献结果进行了数值比较,发现本文所得结果优于有关文献结果。     

基于有限元方法的运动磁体电磁场的计算

由于导体与磁体发生相对运动,会在导体中激发出电动势。假如在同等情况下撤去导体,即磁体相对周围空间发生相对运动,运动磁体必然引起周围磁场的变化,从而激发出电场。麦克斯韦方程组是求解电磁场问题的基本依据,而有限元方法凭借其自身特点广泛应用于电磁场计算仿真中。本文在麦克斯韦方程组的基础上,推导出应用于运动磁体电磁场的理论模型,利用有限元软件ANSYS对磁体电磁场进行仿真计算,并对结果进行了详尽的分析。