二维N-S方程的Fourier非线性Galerkin方法*

本文对周期边界条件Navier-Stokes方程,证明了其Fourier非线性Galerkin逼近解的存在唯一性,同时给出了逼近解的误差估计。     

二维N－S方程的Fourier非线性Galerkin方法

本文对周期边界条件Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程，证明了其Ｆｏｕｒｉｅｒ非线性Ｇａｌｅｒｋｉｎ逼近解的存在唯一性，同时给出了逼近解的误差估计．     

基于时滞惯性流形的非线性Galerkin算法

针对Marion-Temam型非线性Galerkin方法可行性强烈依赖于最小解题规模的不足,利用时滞惯性流形的新思想,以二维Navier-Stokes方程为例,给出了该类非线性Galerkin方法的一种改进形式,并证明了改进后的方法在保持原方法优越性的同时,其可行性条件得到了很大的改善,从而,给出的是一种可行的高效稳定算法。     

一类奇摄动非线性边值问题激波解的Sinc—Galerkin方法

讨论了一类非线性奇摄动方程的激波问题．利用Sinc—Galerkin方法,构造出边值问题的激波解,并由Newton法得到其近似解．     

Navier-Stokes方程的最佳有限元非线性Galerkin算法

1．引言对于Navier－Stokes方程有限元数值求解方面的研究已有很多的文章和专著,多数是采用有限元Galerkin算法,例见文献[1-4]．然而,由于Navier-Stokes方程在大雷诺数时有其强的非线性性和对时间土的长期依赖性,用计算机求解Navier－Stokes方程在速度和容量方面是难以承受的．为了克服这些困难,最近人们提出了有限元非线性Galerkin算法,见文献卜8］,然而这种算法只是在某一有限时刻之后具有好的收敛速度,在初始时刻的某一区间不能达到好的收敛速度．本文应用Taylor展开技术导出了数值求解二维非定常Navier－Stokes方程的最佳…     

非线性Galerkin算法的收敛性和复杂性

本文给出了数值求解非线性发展方程的全离散非线性Ｇａｌｅｒｋｉｎ算法,即将空间离散时的谱非线性Ｇａｌｅｒｋｉｎ算法和时间离散的Ｅｕｌｅｒ差分格式相结合,得到了显式和隐式两种全离散数值格式,相应地也考虑了显式和隐式的Ｇａｌｅｒｋｉｎ全离散格式,并分别分析了上述四种全离散格式的收敛性和复杂性,经过比较得出结论;在某些约束条件下,非线性Ｇａｌｅｒｋｉｎ算法和Ｇａｌｅｒｋｉｎ算法具有相同阶的收敛速度,然而前     

一类非线性双曲-抛物耦合问题的A.D.I.Galerkin方法

1　引　言考虑三维非线性双曲 -抛物耦合初边值问题 :utt- . (a1 (X,t,u) u) +b1 (X,t,u,v) . u　　　　 +α1 e. v =f(X,t,u,v) ,X∈Ω,t∈ J.vt-a2 Δv +b2 (X,t,u,v) . v　　　　 +α2 e. ut=g(X,t,u,v) ,X∈Ω,t∈ J.u(X,t) =v(X,t) =0 , X∈ Ω ,t∈ J.u(X,0 ) =u0 (X) ,ut(X,0 ) =ut0 (X) ,v(X,0 ) =v0 (X) ,X∈Ω.(1 .1 )其中 ,X=(x1 ,x2 ,x3) ,Ω=(c1 ,d1 )× (c2 ,d2 )× (c3,d3)为 R3中矩形区域 ,边界 Ω . J=[0 ,T] ,T>0为一正常数 .b1 ,b2 ,f,g均为已知光滑函数 (其中 b1 ,b2 为向量函数 ) ,且关于 u,v满足 L…     

关于Kuramoto-Sivashinsky方程的非线性Galerkin方法之注记*

本文致力于讨论求解Kuramoto-Sivashinsky方程的非线性Galerkin方法,我们采用了sm个小尺度分量作反馈,并给出了收敛性结果,分析了误差估计．结论表明我们的修正方法是十分有效的．     

关于二维Navier-Stokes方程非线性Galerkin校正的注记

本文在对二维Navier-Stokes方程及其近似惯性流形领域估计的基础上，讨论了非线性Galerkin方法校正量的一种可能的最优选取。     

Galerkin approximation for elliptic PDEs on spheres

We discuss a Galerkin approximation scheme for the elliptic partial differential equation -Δu+ω²u=f on SⁿRⁿ⁺¹. Here Δ is the Laplace–Beltrami operator on Sⁿ, ω is a non-zero constant and f belongs to C^2k-2(Sⁿ), where kn/4+1, k is an integer. The shifts of a spherical basis function φ with φH^τ(Sⁿ) and τ>2kn/2+2 are used to construct an approximate solution. An H¹(Sⁿ)-error estimate is derived under the assumption that the exact solution u belongs to C^2k(Sⁿ).     

一类四阶非线性系统的全局渐近稳定性

运用类比法,构造了一类四阶非线性系统的李雅普诺夫函数,得到其平凡解全局渐近稳定的充分性准则,推广并改进了有关这类系统的其它结果.     

The spectral method for the flow between two concentric rotating spheres, part II: The full discrete nonlinear Legendre-Galerkin method

The nonlinear Galerkin methods are numerical schemes for evolutionary partial differential equations based on the theory of inertial manifolds and approximate inertial manifolds. In this paper, we consider the flow between two concentric rotating spheres, and combine the Legendre-Galerkin spectral methods in Part I together with the nonlinear Galerkin method, then construct the full discrete nonlinear Legendre-Galerkin spectral scheme, and derive the stability conditions and its error estimate.     

Torsional oscillations in symmetrical structures

A two-time perturbation technique is used to study the lateral and torsional motions of a nonlinear symmetrical structure subject to a lateral sinusoidal ground motion. It is shown that when the ground acceleration frequency is about one-third of or three times the natural frequency of the lateral motion, the symmetrical structure is particularly susceptible to torsional oscillations even when the natural frequency of torsion is not close to the natural frequency of the lateral motion. The implication of this type of nonlinear coupling between the lateral and torsional motions in real structures subject to earthquakes is also discussed.     

NONLINEAR GALERKIN METHOD FOR NAVIER-STOKES EQUATIONS WITH STREAM-VORTICITY FORM

I Let D be a launder domain in Rz with Lipehitz continuous bodare I'. ac consider the stream-vortidty form of hmedependent Navier-stokes Muahons describing the 'flow Of a ~ incompreSSible nuid confined in Dwhere to and & are vorticity and stream function. BecaUSe the action (1) doeS not include the differentialten z, ~ tie ~ con&tion of' dab at In tthe Paper, we give a ho element n~ Galerkin ~, acs ~ is ~ an tab finite element spaceS X. and X* for the aPPmxhaation of the ~ ac v~ fUncti…     

Best estimates of RBF-based meshless Galerkin methods for Dirichlet problem

In this paper, Galerkin methods based on the radial basis functions to deal with the partial differential equations are discussed. The best error estimates for this method are obtained.     

Global dynamics of the periodic logistic system with periodic impulsive perturbations

This paper studies the global behaviors of the periodic logistic system with periodic impulsive perturbations. The results of D.D. Bainov and P.S. Simeonov (1993) are extended and dynamics different from the corresponding continuous system are found. It is shown that the system may have a unique positive periodic solution which is globally asymptotically stable, or go extinct when the two periods are rational dependent. When they are rational independent, the system has no periodic solutions, however, still has a global attractor or go extinct under some conditions.     

奇摄动非线性状态调节器问题的渐近解*

我们将寻求最优控制和奇摄动非线性状态调节器问题的相应轨道.在适当的假设下将有可能去完成当ε→0时一致有效的渐近解.     

某类二阶非线性系统初值问题的奇摄动*

本文研究某类二阶非线性向量微分方程初值问题ε'x\"=f(t,x,x',ε),x(0,ε)=a,x'(0,ε)=β的奇摄动,其中r>0为任意常数,ε>0为小参数,x,f,α,β∈Rn.在适当的假设下,利用多参数展开法和对角化技巧,证得摄动问题解的存在和导出解的高阶的一致有效渐近展开式.