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1.
不增加基点,仅摄动二阶ENO格式的系数(简记为MCENO),得到一类求解双曲型守恒律方程的三阶MCENO格式.由MCENO格式的构造过程可以看出,MCENO格式保留了ENO格式的许多性质,例如本质无振荡性、TVB性质等,且能提高一阶精度.进一步,利用MCENO格式模拟二维Rayleigh-Taylor(RT)不稳定性和Lax激波管的数值求解问题.数值结果表明,t=2.0时,MCENO格式的密度曲线处于三阶WENO格式和五阶WENO格式之间,是一个高效高精度格式.值得注意的是,三阶MCENO格式,三阶WENO格式和五阶WENO格式的CPU时间之比为0.62:1:2.19.表明相对于原始ENO格式,MCENO格式在光滑区域有较高精度,能提高格式精度.  相似文献   

2.
本文发展了非定常对流扩散方程的非线性保正格式.该格式为单元中心型有限体积格式,保持局部通量的守恒性,适用于任意星形多边形网格,本文证明了该离散格式解的存在性,并给出数值结果,表明该格式具有二阶精度.  相似文献   

3.
王婷  唐烁 《应用数学和力学》2017,38(12):1342-1358
借鉴含导数两步迭代格式转化成不含导数两步迭代格式的思想,提出了一种更通用的两步无导数迭代格式,通过权值保证了两步无导迭代格式达到最优阶;利用自加速参数和Newton(牛顿)插值多项式得到了两参和三参有记忆迭代格式,并与已有的两参和三参有记忆迭代格式进行比较;给出了几个格式的吸引域,比较了几个迭代格式的性能.  相似文献   

4.
对三维抛物型方程,构造了一个高精度恒稳定的PC格式,格式的截断误差阶达到O(△t^2+△x^4),通过数值实例验证了所得格式较现有的同类格式的精度提高了二位以上有效数字;然后将Richardson外推法应用于本文格式,得到了具有O(△t^3+△x^6)阶精度的近似解,并将所得格式推广到了四维情形.  相似文献   

5.
对于热传导方程构造了两个高阶精度的差分格式,一个是三层七点显格式,另一个是三层九点隐格式.证明了差分格式的收敛性和稳定性,最后给出数值计算结果.  相似文献   

6.
在WENO-Z型格式框架下,基于高阶全局光滑因子,在非线性权建立过程中引入参数,通过收敛性分析确定参数取值范围,兼顾精确性与不振荡性,得到参数最佳取值.最终得到一个低耗散、高分辨率的三阶WENO差分格式,该格式在函数一阶极值点处仍保持预期三阶精度.最后通过精确解算例验证了格式在各种类型极值点处精度恢复情况,并通过一、二维Euler方程组经典算例测试了格式的低耗散、高分辨特性.结果表明,该文格式是一个性能优良的激波捕捉格式.  相似文献   

7.
低耗散、高分辨率激波捕捉格式对含激波流场的数值模拟具有重要意义.在传统三阶WENO格式(WENO-JS3)和三阶WENO Z格式(WENO-Z3)基础上,基于映射函数,给出WENO-M3、WENO MZ3格式.选用Sod激波管、激波与熵波相互作用、双爆轰波碰撞及双Mach(马赫)反射等经典算例,考察上述格式的计算性能.数值结果表明,WENO-MZ3格式相较其他格式具有耗散低、对流场结构分辨率高的特性.为了进一步扩展WENO-MZ3格式的应用范围,采用该格式数值研究封闭方形舱室内柱形高压、高密度气体爆炸波传播过程,波系演化规律以及壁面典型测点压力载荷.数值计算结果表明WENO-MZ3格式能够较好地模拟包含高压比、高密度比的爆炸波且给出数值耗散较小的壁面压力载荷.  相似文献   

8.
本文对一类非自共轭非线性Schroedinger方程提出了一种三层差分格式,并证明了该格式的收敛性与稳定性,这种格式不需叠代,故计算速度比C-N格式快,数值计算结果表明,该格式是有效的和可靠的。  相似文献   

9.
本文考虑一维单个守恒律方程,对其设计了一个基于熵耗散的非线性守恒型差分格式.本格式的数值流函数是Lax-Freidrichs格式和Lax-Wendroff格式数值流函数的凸组合,凸组合中的系数是由考虑耗散熵来决定的.这样在解的光滑区域内,格式几乎、甚至完全是Lax-Wendroff格式,而在解的间断处,格式几乎、甚至完全是Lax—Freidrichs格式.从而消除了间断附近的非物理振荡,实现了计算的非线性稳定性.理论分析表明本格式在解的非极值点处是二阶精度的,而在解的极值点处至少有一阶精度.数值试验表明格式是有效的.  相似文献   

10.
色散方程的一类新的并行交替分段隐格式   总被引:14,自引:0,他引:14  
王文洽 《计算数学》2005,27(2):129-140
本文给出了一组逼近色散方程的非对称差分格式,并用这组格式和对称的Crank-Nicolson型格式构造了求解色散方程的并行交替分段差分隐格式.这个格式是无条件稳定的,能直接在并行计算机上使用.数值试验表明,这个格式有很好的精度.  相似文献   

11.
In this work, we investigate the existence and the uniqueness of solutions for the nonlocal elliptic system involving a singular nonlinearity as follows: $$ \left\{\begin{array}{ll} (-\Delta_p)^su = a(x)|u|^{q-2}u +\frac{1-\alpha}{2-\alpha-\beta} c(x)|u|^{-\alpha}|v|^{1-\beta}, \quad \text{in }\Omega,\ (-\Delta_p)^s v= b(x)|v|^{q-2}v +\frac{1-\beta}{2-\alpha-\beta} c(x)|u|^{1-\alpha}|v|^{-\beta}, \quad \text{in }\Omega,\ u=v = 0 ,\;\;\mbox{ in }\,\mathbb{R}^N\setminus\Omega, \end{array} \right. $$ where $\Omega $ is a bounded domain in $\mathbb{R}^{n}$ with smooth boundary, $0<\alpha <1,$ $0<\beta <1,$ $2-\alpha -\beta 相似文献   

12.
The authors consider the problem: -div(p▽u) = uq-1 λu, u > 0 inΩ, u = 0 on (?)Ω, whereΩis a bounded domain in Rn, n≥3, p :Ω→R is a given positive weight such that p∈H1 (Ω)∩C(Ω),λis a real constant and q = 2n/n-2, and study the effect of the behavior of p near its minima and the impact of the geometry of domain on the existence of solutions for the above problem.  相似文献   

13.
On a General Projection Algorithm for Variational Inequalities   总被引:14,自引:0,他引:14  
Let H be a real Hilbert space with norm and inner product denoted by and . Let K be a nonempty closed convex set of H, and let f be a linear continuous functional on H. Let A, T, g be nonlinear operators from H into itself, and let be a point-to-set mapping. We deal with the problem of finding uK such that g(u)K(u) and the following relation is satisfied: , where >0 is a constant, which is called a general strong quasi-variational inequality. We give a general and unified iterative algorithm for finding the approximate solution to this problem by exploiting the projection method, and prove the existence of the solution to this problem and the convergence of the iterative sequence generated by this algorithm.  相似文献   

14.
The authors study the following Dirichlet problem of a system involving fractional (p, q)-Laplacian operators:
$$\left\{ {\begin{array}{*{20}{c}} {\left( { - \Delta } \right)_p^su = \lambda a\left( x \right){{\left| u \right|}^{p - 2}}u + \lambda b\left( x \right){{\left| u \right|}^{\alpha - 2}}{{\left| v \right|}^\beta }u + \frac{{\mu \left( x \right)}}{{\alpha \delta }}{{\left| u \right|}^{\gamma - 2}}{{\left| v \right|}^\delta }uin\Omega ,} \\ {\left( { - \Delta } \right)_q^sv = \lambda c\left( x \right){{\left| v \right|}^{q - 2}}v + \lambda b\left( x \right){{\left| u \right|}^\alpha }{{\left| v \right|}^{\beta - 2}}v + \frac{{\mu \left( x \right)}}{{\beta \gamma }}{{\left| u \right|}^\gamma }{{\left| v \right|}^{\delta - 2}}vin\Omega ,} \\ {u = v = 0on{\mathbb{R}^N}\backslash \Omega ,} \end{array}} \right.$$
where λ > 0 is a real parameter, Ω is a bounded domain in R N , with boundary ?Ω Lipschitz continuous, s ∈ (0, 1), 1 < pq < ∞, sq < N, while (?Δ) p s u is the fractional p-Laplacian operator of u and, similarly, (?Δ) q s v is the fractional q-Laplacian operator of v. Since possibly pq, the classical definitions of the Nehari manifold for systems and of the Fibering mapping are not suitable. In this paper, the authors modify these definitions to solve the Dirichlet problem above. Then, by virtue of the properties of the first eigenvalue λ1 for a related system, they prove that there exists a positive solution for the problem when λ < λ1 by the modified definitions. Moreover, the authors obtain the bifurcation property when λ → λ1-. Finally, thanks to the Picone identity, a nonexistence result is also obtained when λ ≥ λ1.
  相似文献   

15.
Let K be a nonempty closed convex subset of a real Hilbert space H. The approximate solvability of a system of nonlinear variational inequality problems, based on the convergence of projection methods, is discussed as follows: find an element (x*, y*)K×K such that
where T: K×KH is a nonlinear mapping on K×K.  相似文献   

16.
In the present paper, the modified Runge-Kutta method is constructed, and it is proved that the modified Runge-Kutta method preserves the order of accuracy of the original one. The necessary and sufficient conditions under which the modified Runge-Kutta methods with the variable mesh are asymptotically stable are given. As a result, the -methods with , the odd stage Gauss-Legendre methods and the even stage Lobatto IIIA and IIIB methods are asymptotically stable. Some experiments are given.

  相似文献   


17.
The authors study the existence of homoclinic type solutions for the following system of diffusion equations on R × RN:{■tu-xu + b ·▽xu + au + V(t,x)v = Hv(t,x,u,v),-■tv-xv-b·▽xv + av + V(t,x)u = Hu(t,x,u,v),where z =(u,v):R × RN → Rm × Rm,a > 0,b =(b1,···,bN) is a constant vector and V ∈ C(R × RN,R),H ∈ C1(R × RN × R2m,R).Under suitable conditions on V(t,x) and the nonlinearity for H(t,x,z),at least one non-stationary homoclinic solution with least energy is obtained.  相似文献   

18.
A new approximate proximal point algorithm for maximal monotone operator   总被引:7,自引:0,他引:7  
The problem concerned in this paper is the set-valued equation 0 ∈T(z) where T is a maximal monotone operator. For given xk and βk > 0, some existing approximate proximal point algorithms take x~(k+1) = xk such thatwhere {ηk} is a non-negative summable sequence. Instead of xk+1 = xk , the new iterate of the proposing method is given bywhere Ω is the domain of T and PΩ(·) denotes the projection on Ω. The convergence is proved under a significantly relaxed restriction supk>0 ηk<1.  相似文献   

19.
Interior-point methods (IPMs) for semidefinite optimization (SDO) have been studied intensively, due to their polynomial complexity and practical efficiency. Recently, J. Peng et al. introduced so-called self-regular kernel (and barrier) functions and designed primal-dual interior-point algorithms based on self-regular proximities for linear optimization (LO) problems. They also extended the approach for LO to SDO. In this paper we present a primal-dual interior-point algorithm for SDO problems based on a simple kernel function which was first presented at the Proceedings of Industrial Symposium and Optimization Day, Australia, November 2002; the function is not self-regular. We derive the complexity analysis for algorithms based on this kernel function, both with large- and small-updates. The complexity bounds are and , respectively, which are as good as those in the linear case. Mathematics Subject Classifications (2000) 90C22, 90C31.  相似文献   

20.
Dimensionally unbounded problems are frequently encountered in practice, such as in simulations of stochastic processes, in particle and light transport problems and in the problems of mathematical finance. This paper considers quasi-Monte Carlo integration algorithms for weighted classes of functions of infinitely many variables, in which the dependence of functions on successive variables is increasingly limited. The dependence is modeled by a sequence of weights. The integrands belong to rather general reproducing kernel Hilbert spaces that can be decomposed as the direct sum of a series of their subspaces, each subspace containing functions of only a finite number of variables. The theory of reproducing kernels is used to derive a quadrature error bound, which is the product of two terms: the generalized discrepancy and the generalized variation.

Tractability means that the minimal number of function evaluations needed to reduce the initial integration error by a factor is bounded by for some exponent and some positive constant . The -exponent of tractability is defined as the smallest power of in these bounds. It is shown by using Monte Carlo quadrature that the -exponent is no greater than 2 for these weighted classes of integrands. Under a somewhat stronger assumption on the weights and for a popular choice of the reproducing kernel it is shown constructively using the Halton sequence that the -exponent of tractability is 1, which implies that infinite dimensional integration is no harder than one-dimensional integration.

  相似文献   


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