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991.
Takahiro Sumi Takuji Kurotaki Jun Hiyama 《International Journal of Computational Fluid Dynamics》2013,27(9-10):335-350
In practical fluid computation with structured grids around complex geometries, singular points with metric discontinuity can frequently be found. Generally, the grid singularities may cause numerical oscillations when some high-order finite difference scheme is applied. Recently, an excellent theory has been proposed which solves the above singular problem by block decomposition along the singular surface and by imposition of the characteristic interface conditions (CIC) on the block interface. However, the original theory has constraints on the mathematical treatment of the block interface, and therefore prevents numerical flexibility from a practical point of view. In this article, in order to extend the functions of the original CIC, we propose the generalized characteristic interface conditions (GCIC). Proper numerical test analysis is conducted to validate the performance of the GCIC, and as a practical application, multi-block computation is performed with the GCIC applied to complex geometry. 相似文献
992.
A seed laser oscillating at different frequencies is proved to have the potential to mitigate the stimulated Brillouin scattering(SBS) effect in a fiber amplifier,which may increase the emission power of a coherent beam combination(CBC) system greatly.In this study,a basic mathematical model describing the multi-wavelength CBC is proposed on the fundamentals of CBC.A useful method for estimating the combination effect and analysing the feasibility and the validity of the multi-wavelength coherent combination is provided.In the numerical analysis,accordant results with four-wavelength four-channel CBC experiments are obtained.Through calculations of some examples with certain spectra,the unanticipated excellent combination effect with a few frequencies involved is explained,and the dependence of the combination effect on the variance of the amplifier chain length and the channel number is clarified. 相似文献
993.
994.
在GPS网络差分定位技术中,用户站与参考站间的高程差异会引起对流层误差改正数中存在系统性偏差,造成对流层改正精度降低,影响用户定位的效果。在常规两维线性组合模型的基础上,考虑高程因素影响,利用三维位置信息对内插模型参数进行约束,将对流程延迟改正数分为距离相关和高程相关两部分,通过卡尔曼滤波器分别估计,提出了一种能修正高程偏差的对流层三维线性组合模型。以重庆连续运行参考站系统中5个站作为研究对象,实验验证结果表明,在地形起伏较大的地区,三维线性组合模型可将对流层改正精度从20~40 cm提高到5~6 cm,相对于常规方法提高了4~6倍,消除了网络差分定位中高程差引起的对流层改正系统偏差。 相似文献
995.
996.
In this paper an efficient computational method based on extending the sensitivity approach(SA) is proposed to find an analytic exact solution of nonlinear differential difference equations.In this manner we avoid solving the nonlinear problem directly.By extension of sensitivity approach for differential difference equations(DDEs),the nonlinear original problem is transformed into infinite linear differential difference equations,which should be solved in a recursive manner.Then the exact solution is determined in the form of infinite terms series and by intercepting series an approximate solution is obtained.Numerical examples are employed to show the effectiveness of the proposed approach. 相似文献
997.
Finite Difference/Element Method for a Two-Dimensional Modified Fractional Diffusion Equation 下载免费PDF全文
We present the finite difference/element method for a
two-dimensional modified fractional diffusion equation. The analysis
is carried out first for the time semi-discrete scheme, and then for
the full discrete scheme. The time discretization is based on the
$L1$-approximation for the fractional derivative terms and the
second-order backward differentiation formula for the classical
first order derivative term. We use finite element method for the
spatial approximation in full discrete scheme. We show that both the
semi-discrete and full discrete schemes are unconditionally stable
and convergent. Moreover, the optimal convergence rate is obtained.
Finally, some numerical examples are tested in the case of one and
two space dimensions and the numerical results confirm our
theoretical analysis. 相似文献
998.
In this article, two split-step finite difference methods for Schrödinger-KdV equations are formulated and investigated. The main features of our methods are based on:(i) The applications of split-step technique for Schrödingerlike equation in time. (ii) The utilizations of high-order finite difference method for KdV-like equation in spatial discretization. (iii) Our methods are of spectral-like accuracy in space and can be realized by fast Fourier transform efficiently. Numerical experiments are conducted to illustrate the efficiency and accuracy of our numerical methods. 相似文献
999.
依据欧拉定理,研究了边数差和着色数计算公式,对四色猜想进行了研究.借助四面体顶点数与面积数相等的原则、多面体边数不变的原则和多余理论,用边数差数学计算方法论证了四色猜想.用简单的数学公式和几何作图方法说明了四色猜想的合理性,为其提供了可靠的理论依据.用“三色包点”和“以面切体”的几何作图法,证明多面体和平面地图的着色数恒为4;非三色包点的图形,可以通过“以面切体”的方法转换成三色包点的图形;使用多余国家、多余边数的数学技巧代替计算机使用的不可避免性、可约性是合适的.理论分析及实例论证表明该方法简单可行. 相似文献
1000.
建立了不可压缩Navier-Stokes方程的Crank-Nicolson有限差分方法,数值模拟水槽晃动中流场及其涡流的数值变化规律。将数值解与解析解和前人的数值解进行比较,数值验证了不可压缩Naver-Stokes方程有限差分方法的有效性。通过数值模拟得到水槽在不同程度的倾斜激励晃动下流场及涡流的数值变换规律,当倾斜激励晃动的频率接近或远离共振频率时,水槽涡场的变化逐步由双涡变成单涡,再到不规则的涡场。当倾斜激励晃动的频率靠近共振频率ω_p=0.95ω_1附近时,水槽流场上部形成一个小涡,然后小涡扩大成整个水槽中的大涡,大涡下沉分裂成两个单涡,最后在底部消失;当倾斜激励晃动的频率在ω_p=0.75ω_1附近时,水槽底部形成一个小涡,然后扩大成大的单涡,最后在自由面消失;当倾斜激励晃动的频率在ω_p=0.55ω_1附近时,水槽底部出现小涡,然后扩大成大的单涡,大涡在自由面消失,继而出现不规则的大涡和不规则的小涡。 相似文献