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61.
Qiaolin He 《advances in applied mathematics and mechanics.》2012,4(2):238-249
In this paper, we propose a new two-level preconditioned C-G method
which uses the quadratic smoothing and the linear correction in distorted but topologically
structured grid. The CPU time of this method is less than that of the
multigrid preconditioned C-G method (MGCG) using the quadratic element, but
their accuracy is almost the same. Numerical experiments and eigenvalue analysis
are given and the results show that the proposed two-level preconditioned method
is efficient. 相似文献
62.
63.
构造了一类具有一阶弹性的函数.该函数是级联4个具有一对拟线性变量的子函数得到的.给出了新函数代数次数不增加的充分必要条件,代数免疫阶不增加的必要条件.选取的初始函数不满足代数次数和代数免疫不增加的必要条件,那么得到函数和初始函数相比,代数免疫至少增加1阶,代数次数增加1次,并且具有1阶弹性. 相似文献
64.
65.
66.
Hitoshi Sugiyama Chiriki Watanabe Naoto Kato 《International Journal of Computational Fluid Dynamics》2013,27(8):335-348
A numerical analysis has been performed for a developing turbulent flow in a rotating U-bend of strong curvature with rib-roughened walls using an anisotropic turbulent model. In this calculation, an algebraic Reynolds stress model is used to precisely predict Reynolds stresses, and a boundary-fitted coordinate system is introduced as a method of coordinate transformation to set the exact boundary conditions along the complicated shape of U-bend with rib-roughened walls. Calculated results for mean velocity and Reynolds stresses are compared to the experimental data in order to validate the proposed numerical method and the algebraic Reynolds stress model. Although agreement is certainly not perfect in all details, the present method can predict characteristic velocity profiles and reproduce the separated flow generated near the outer wall, which is located just downstream of the curved duct. The Reynolds stresses predicted by the proposed turbulent model agree well with the experimental data, except in regions of flow separation. 相似文献
67.
A. EGELJA M. SCHÄFER F. DURST 《International Journal of Computational Fluid Dynamics》2013,27(3):213-224
A numerical scheme for the prediction of free surface flows is presented and investigated. The method is based on an adaptive grid Eulerian finite-volume method, where non-orthogonal boundary-fitted moving grids are employed to follow the free surface. The underlying flow solver consists in a pressure-correction scheme of SIMPLE type with multigrid acceleration, which is iteratively combined with the moving grid technique. Several numerical examples are considered to illustrate the capabilities of the approach. 相似文献
68.
The prolongation structure methodologies of Wahlquist-Estabrook [H.D. Wahlquist and F.B. Estabrook, {J. Math. Phys.} 16 (1975) 1] for nonlinear differential equations are applied to a more general set of coupled integrable dispersionless system. Based on the obtained prolongation structure, a Lie-Algebra valued connection of a closed ideal of exterior differential forms related to the above system is constructed. A Lie-Algebra representation of some hidden structural symmetries of the previous system, its Bäcklund transformation using the Riccati form of the linear eigenvalue problem and their general corresponding Lax-representation are derived. In the wake of the previous results, we extend the above prolongation scheme to higher-dimensional systems from which a new (2+1)-dimensional coupled integrable dispersionless system is unveiled along with its inverse scattering formulation, which applications are straightforward in nonlinear optics where additional propagating dimension deserves some attention. 相似文献
69.
在基于漂移-扩散模型的三维半导体器件数值模拟中,通过有限体积法进行数值离散,采用完全耦合的牛顿迭代求解非线性代数方程组,并使用基于代数多重网格预条件子的GMRES方法求解牛顿迭代中的线性方程组,构造一种稳健且高度可扩展的非结构四面体网格上求解半导体方程的并行算法.基于PHG平台实现该算法的并行计算程序,并对PN结和MOS场效应晶体管等问题进行了最大网格规模达到5亿单元、最大并行规模达到1 024进程的大规模数值模拟实验,结果表明,该算法计算效率高,可扩展性好. 相似文献
70.
PRECONDITIONING HIGHER ORDER FINITE ELEMENT SYSTEMS BY ALGEBRAIC MULTIGRID METHOD OF LINEAR ELEMENTS
Yun-qing Huang Shi Shu Xi-jun Yu 《计算数学(英文版)》2006,24(5):657-664
We present and analyze a robust preconditioned conjugate gradient method for the higher order Lagrangian finite element systems of a class of elliptic problems. An auxiliary linear element stiffness matrix is chosen to be the preconditioner for higher order finite elements. Then an algebraic multigrid method of linear finite element is applied for solving the preconditioner. The optimal condition number which is independent of the mesh size is obtained. Numerical experiments confirm the efficiency of the algorithm. 相似文献