共查询到20条相似文献,搜索用时 171 毫秒
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本文给出了数值求解以流函数表示的Navier-Stokes方程的交替方向部分隐式和交替方向完全隐式方法;作为算例,计算了低雷诺数的二维方腔流动问题,并与已知结果进行了比较。 相似文献
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给出了两种适用于二维单步交替方向隐式时域有限差分(2-D Leapfrog ADI-FDTD)方法的吸收边界:Mur边界和卷积完全匹配层(CPML)边界。单步交替方向隐式时域有限差分(Leapfrog ADI-FDTD)方法是一种无条件稳定的全隐式差分算法,由于二维空间Leapfrog ADI-FDTD的迭代同时存在显式和隐式方程,故而不同电磁分量的边界条件也存在差异。从原理出发,推导了适用于2-D Leapfrog ADI-FDTD方法的CPML边界条件,并与一阶Mur边界进行比较,利用自由空间的反射误差来表征两种边界的吸收性能,简要总结了两种吸收边界的优缺点。 相似文献
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求解隐式差分方程的并行算法 总被引:3,自引:0,他引:3
本文研究了求解隐式差分方程的并行算法,其基本想法是把差分方程组化为若干个子方程组来求解,文中给出了直接法和迭代法,证明了迭代法的收敛性。为了说明分段隐式迭代方法的有效性,文中针对扩散方程的具体例子给出了数值试验计算结果。 相似文献
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平面光波导器件时域有限差分束传输法分析中边界和初始条件的处理 总被引:4,自引:4,他引:0
从慢变包络(SVEA)时域光传输方程出发,对比了综合道格拉斯(GD)和传统的中心差分(CN)两种离散化格式,指出GD法比CN法精度有了很大提高.重点讨论了GD法的TD-BPM边界处理问题,给出了吸收边界和透明边界离散的显式和隐式表达式,分析并确定了交替方向隐式法(ADIM)的边界处理方式;同时,对激励源加入的连接边界进行了仔细讨论.结果表明对于隐式GD-TD-BPM法边界处理应采用隐式,中间激励更能反映光波导反射场的情况. 相似文献
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海洋自然噪声场空间互功率谱 总被引:1,自引:0,他引:1
本文以海洋自然噪声场局部谱理论为基础,给出了海洋自然噪声场空间互功率谱的一般表示式,计算了几种典型情况下的空间互功率谱。对声速均匀分布的深海模型,得到的结果比Cron和Sherman(1962年)多了一个附加项,即不均匀平面波对噪声场的贡献。当接收器深度远大于接收器之间的间距时,此附加项可以忽略不计。最后,将某些理论计算的结果同早先获得的实验资料作了比较。 相似文献
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本文提出两个修正的PST迭代格式,并给出了数值试验的对比结果。试验结果表明,该格式能在一定程度上降低对初值的要求,也能减少一定的计算量。 相似文献
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ICCG方法是解线性代数方程组较为理想的方法,但它仅适用于具有正定对称的系数阵。本文介绍的TCG方法便足改造过的ICCG方法,它适用于一般非奇异的非正定对称阵。TCG方法比常用的JLUCG方法,对于非定常问题,可提高效率18%,特别是取用SIP不完全L、U分解作预条件时,可提高效率40%,是计算非正定对称阵较为理想的迭代法之一。本文推导出在消去法不完全L,U分解下的TCG方法,并用数值结果论证出它比ILUCG方法加速收敛的所在。 相似文献
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本文发展了量子激发态能量与波函数的最陡下降微扰理论计算方法,该方法避免了普通微扰理论所需要的对于参考态的无限求和困难,并能通过逐步迭代计算逼近于体系精确的本征函数和本征值。只要保持激发态试探波函数正交于其对称性相同的低激发态或基态的波函数,避免计算过程中的变分坍陷,本文的方法能用于求精确的激发态能量和波函数。
关键词: 相似文献
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We consider a measure defined on a complex contour and its associated orthogonal polynomials. The action of a polynomial transformation on the measure and the transformation laws of the corresponding orthogonal polynomials are given. Iterating the transformation provides an invariant measure, whose support is the Julia set corresponding to the polynomial transformation. It appears that, up to a constant, the iterated polynomials generated by the initial mapping form a subset of the invariant set of orthogonal polynomials, which fulfill a three term recursion relation. An algorithm is given to compute the coefficients of this recursion relation, which can be interpreted as a linear extension of the iterative procedure. 相似文献
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计算流体中一个改进的强隐式格式及迭代的收敛性 总被引:1,自引:0,他引:1
本文分析了Stone引入辅助矩阵Ã将五对角阵A变为七对角阵A+Ã的过程,指出Stone引入的辅助阵Ã不具备对称性,由此会给迭代收敛的分析工作带来困难。在此分析的基础上构造了一个对称的辅助矩阵,当A为对称时可使A+Ã对称正定。给出选取最优迭代参数ω的公式和办法。通过典型算例对这种改进的强隐式格式的数值稳定性作了验证。 相似文献
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非结构网格在平面叶栅内湍流流动数值模拟中的应用 总被引:2,自引:1,他引:1
1控制方程和离散方程对二维非定常可压缩粘性流体,雷诺时均Navierstokes方程可写成如下积分形式:式中,0为计算区域;*D为区域边界;Q为守恒变量;F为通量,包括无粘通量F’和粘性通量F”。计算域采用三角形单元离散,三角形的边作为控制体边界,物理量置于单元中心。对每个三角形控制体,方程(1)可写成:·其中,Q;表示单元的守恒变量值;aC和Vi分别表示控制体的边界和面积,为计算式(2中右端值,将单元所有边界通量相加,最后可得如下方程:式中k(i)为单元边界,只,j为通过单元界面的通量,凸马为界面长度。2无粘通量本文采… 相似文献
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本文给出用Young盘表达fN组态谱项波函数的系统方法,特别是表达简并谱项波函数的方法,使得谱项的波函数和Racah群链的态分类一致。
关键词: 相似文献
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C.K.W. Tam 《Journal of sound and vibration》1976,45(1):91-104
A computational procedure based on the Galerkin method is developed to study the sound transmission and reflection characteristics of circularly curved bends of rectangular ducts. This procedure is adaptable to routine computer calculation. An important component of the computer program consists of a QR iterative algorithm which solves the matrix eigenvalue problem generated by the Galerkin method. The present procedure produced very satisfactory convergent results when applied even to cases where the incident wave has high frequency and high wave mode numbers. Some properties of the Galerkin solution are investigated. Its relationship to the classical solution by the method of separation of variables is discussed. 相似文献
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The operation of disentangling is the key to Feynman's operational calculi for noncommuting operators. Hence, formulas which simplify this procedure under various conditions are central to the subject. The main results here make it possible to carry out the disentangling in an iterative manner. The linear (alternatively, bilinear) term alluded to in the title of the paper refers to the first (alternatively, first and second) step (or steps) of the process. These results have many further consequences some of which are given in this paper. 相似文献
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V. S. Pavelyev V. A. Soifer M. Duparre R. Kowarschik B. Ludge B. Kley 《Optics and Lasers in Engineering》1998,29(4-5)
We present results of iterative calculation, manufacture and experimental as well as theoretical investigations of a novel diffractive optical element (DOE) which transforms a Gaussian TEM00 input beam into a unimodal Gauss–Hermite (1, 0) complex distribution. The iterative calculation procedure is based on the application of the method of generalized projections. The projection operator onto a set of modal functions is implemented through partition of the focal plane into a ‘useful’ and an ‘auxiliary’ domain. This element is manufactured as a 16 level surface profile by (variable dose) electron-beam direct-writing into a PMMA resist film, and a subsequent development procedure of the resist. The final element consists of a fused-silica substrate coated with the structured PMMA film. Both computational and experimental results are presented and demonstrate a good conformity with each other. The achieved results show good prospects of such an approach for the formation of unimodal distributions. 相似文献