Approximate inertial manifolds for the 2d model of atmosphere

In order to understand the mechanism of long term weather prediction and climate, we construct explicitly in this paper an infinite number of approximate inertial manifolds M _j,m for the 2D model of large scale atmosphere to approximate the global attractor of the model. Associated with each manifold, there exists a thin neighborhood of it, into which the orbits of the model enter with a finite time. These neighborhoods contain and localize the global attractor. The thickness of these neighborhoods decreases with increasing m for a fixed j. Moreover we also obtain the time analyticity of the solutions of the model and the behavior of the small structures.     

高维广义Kuramoto-Sivashinsky型方程Fourier拟谱方法的大时间误差估计

在很多物理问题中出现如下方程:Kuramoto在研究反应扩散系统耗散结构时导出了上述方程,Sivashinsky在模拟火焰传播时也得到了它.此外,它还出现在粘性层流和Navier-Stokes方程的分枝解中.在[5-8]中,作者研究了一维情形下周期初值问题的整体吸引子和分枝解;[9]提出了广义KS型方程;[10-14]中研究了它的光滑解的存在性和t→+∞时的渐近性     

The Large Time Convergence of Spectral Method for Generalized Kuramoto-Sivashinsky Equations

In this paper we use the spectral method to analyse the generalized Kuramoto-Sivashinsky equations. We prove the existence and uniqueness of global smooth solution of the equations. Finally, we obtain the error estimation between spectral approximate solution and exact solution on large time.     

A Method for Constructing Traveling Wave Solutions to Nonlinear Evolution Equations

In this paper, an analytical method is proposed to construct explicitly exact and approximate solutions for nonlinear evolution equations. By using this method, some new traveling wave solutions of the Kuramoto-Sivashinsky equation and the Benny equation are obtained explicitly. These solutions include solitary wave solutions, singular traveling wave solutions and periodical wave solutions. These results indicate that in some cases our analytical approach is an effective method to obtain traveling solitary wave solutions of various nonlinear evolution equations. It can also be applied to some related nonlinear dynamical systems.     

Error analysis and applications of the Fourier-Galerkin Runge-Kutta schemes for high-order stiff PDEs

An integrating factor mixed with Runge-Kutta technique is a time integration method that can be efficiently combined with spatial spectral approximations to provide a very high resolution to the smooth solutions of some linear and nonlinear partial differential equations. In this paper, the novel hybrid Fourier-Galerkin Runge-Kutta scheme, with the aid of an integrating factor, is proposed to solve nonlinear high-order stiff PDEs. Error analysis and properties of the scheme are provided. Application to the approximate solution of the nonlinear stiff Korteweg-de Vries (the 3rd order PDE, dispersive equation), Kuramoto-Sivashinsky (the 4th order PDE, dissipative equation) and Kawahara (the 5th order PDE) equations are presented. Comparisons are made between this proposed scheme and the competing method given by Kassam and Trefethen. It is found that for KdV, KS and Kawahara equations, the proposed method is the best.     

Implicit-explicit multistep finite element methods for nonlinear parabolic problems

We approximate the solution of initial boundary value problems for nonlinear parabolic equations. In space we discretize by finite element methods. The discretization in time is based on linear multistep schemes. One part of the equation is discretized implicitly and the other explicitly. The resulting schemes are stable, consistent and very efficient, since their implementation requires at each time step the solution of a linear system with the same matrix for all time levels. We derive optimal order error estimates. The abstract results are applied to the Kuramoto-Sivashinsky and the Cahn-Hilliard equations in one dimension, as well as to a class of reaction diffusion equations in

     

Popular ansatz methods and solitary wave solutions of the Kuramoto-Sivashinsky equation

Some methods to look for exact solutions of nonlinear differential equations are discussed. It is shown that many popular methods are equivalent to each other. Several recent publications with “new” solitary wave solutions for the Kuramoto-Sivashinsky equation are analyzed. We demonstrate that all these solutions coincide with the known ones.      

A Hierarchical Cluster System Based on HortonStrahler Rules for River Networks

We consider a cluster system in which each cluster is characterized by two parameters: an "order" i , following HortonStrahler rules, and a "mass" j following the usual additive rule. Denoting by c _i,j ( t ) the concentration of clusters of order i and mass j at time t , we derive a coagulation-like ordinary differential system for the time dynamics of these clusters. Results about the existence and the behavior of solutions as   t   are obtained; in particular, we prove that   c _i,j ( t ) 0  and   N _i ( c ( t )) 0  as   t ,  where the functional   N _i (·)  measures the total amount of clusters of a given fixed order i . Exact and approximate equations for the time evolution of these functionals are derived. We also present numerical results that suggest the existence of self-similar solutions to these approximate equations and discuss their possible relevance for an interpretation of Horton's law of river numbers.     

广义Kuramoto-Sivashinsky型方程初值问题光滑整体解的存在性与破裂性

本文用积分估计和不动点原理证明了一类广义Kuramoto-Sivashinsky型方程初值问题光滑整体解的存在唯一性,并在不同情况下讨论了解的破裂性,并给出了导致破裂性的充分条件.     

Global solutions to the cylindrically symmetric rotating motion of isentropic gases

We construct global solutions to the Euler equations of compressible isentropic gas dynamics with cylindrically symmetric rotating structure. A shock capturing numerical scheme is introduced to compute such a flow and to construct approximate solutions. The convergence and consistency of the approximate solutions generated from this scheme to the global solutions are proved with the aid of a compensated compactness framework. Earlier work of the authors, which controlled the geometrical source terms, especially as they pertain to radial flow in an unbounded region, 1, is extended here to the 3 × 3 system of cylindrically symmetric rotating flow. Arbitrary data withL bounds are allowed in these results.     

Remarks on Third-Order ODEs Relevant to the Kuramoto-Sivashinsky Equation

We are interested in the third-order ordinary differential equations (ODEs) which are related to the Kuramoto-Sivashinsky equation. So-called steady solutions of the Kuramoto-Sivashinsky equation are known to admit several types; for example, bounded global solutions or periodic solutions. We show that, in addition to these, there exist solutions which blow up on bounded intervals. Moreover, for certain classes of these ODEs, the nonexistence of nontrivial bounded entire solutions is exhibited.     

A finite difference scheme for computing inertial manifolds

A fully discrete method is presented for computing inertial manifolds of dissipative partial differential equations. In particular, only an approximate spectral decomposition of the dominant differential operator needs to be known. The first few of the smallest eigenvalues and eigenvectors of the discretized operator are approximated using the Lanczos algorithm. Numerical experiments are performed for an equation in one space dimension by discretizing the space variable on a sufficiently fine grid. The basic ideas and techniques are exemplified for selected bifurcation diagrams of an integrated form of the Kuramoto-Sivashinsky equation.This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) grant OGP0036901, NSERC and Schweizerischer Nationalfonds zur Förderung der Wissenschaften BEF 0150297, and Forschungsinstitut für Mathematik, ETH Zürich.     

On the behavior of attractors under finite difference approximation

We recall that the long-time behavior of the Kuramoto-Sivashinsky equation is the same as that of a certain finite system of ordinary differential equations. We show how a particular finite difference scheme approximating the Kuramoto-Sivashinsky may be viewed as a small C ¹ perturbation of this system for the grid spacing sufficiently small. As a consequence one may make deductions about how the global attractor and the flow on the attractor behaves under this approximation. For a sufficiently refined grid the long-time behavior of the solutions of the finite difference scheme is a function of the solutions at certain grid points, whose number and position remain fixed as the grid is refined. Though the results are worked out explicitly for the Kuramoto-Sivashinsky equation, the results extend to other infinite-dimensional dissipative systems.     

Time-marching algorithms for initial-boundary value problems based upon “approximate approximations”

New time marching algorithms for solving initial-boundary value problems for semi-linear parabolic and hyperbolic equations are described. With respect to the space variable the discretization is based upon a method of approximate approximation proposed by the second author. We use approximate approximations of the fourth order. In time the algorithms are finite-difference schemes of either first or second approximation order. At each time step the approximate solution is represented by an explicit analytic formula. The algorithms are stable under mild restrictions to the time step which come from the non-linear part of the equation. Some computational results and hints on crucial implementation issues are provided.Supported by the Center for Applied and Industrial Mathematics, Department of Mathematics, Linköping University, Sweden.     

The Global Attractors for the Periodic Initial Value Problem of Generalized Kuramoto-Sivashinsky Type Equations in Multi-dimensions

The existence of global attractors for the periodic initial value problem of generalized Kuramoto-Sivashinsky type equations in multi-dimensions is proved. We also get the estimates of the upper bounds of Hausdorff and fractal dimensions for the global attractors by means of a uniform priori estimates for time.     

Remarks on the resolvent method

The resolvent method for the approximate solution of Fredholm integral equations, proposed by the author, is extended to systems of Fredholm equations and to equations with a weak singularity. The case of a definite irregularity of the integration manifold is also considered.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 58, pp. 5–14, 1976.     

Kuramoto-Sivashinsky方程的B样条Galerkin方法

采用显隐结合的方法对微分算子进行时间离散 ,提出了解 Kuramoto-Sivashinsky方程的全离散 B样条 Galerkin方法 ,由此得到了有限元解的最优阶收敛性及稳定性估计 .最后的数值算例以图形的形式体现了此算法的精确度     

Global attractors and approximate inertial

An abstract nonautonomous differential equation, u' + Au + F(u) = f ( t ) , is considered using assumptions appropriate for systems of reaction-diffusion equations on multi-dimensional spatial domains. A priori estimates establish the existence of absorbing balls in relevant function spaces, and nonsequently the existence of a global attractor is verified in the associated skew-product flow. It is also shown that approximate inertial manifolds exist for this equation. These are finite-dimensional manifolds which have exponentially attracting neighborhoods under the flow. The dimension of the manifold and the thickness of the attracting neighborhood are inversely related.     

Fractional amplitude and phase dynamics in super-diffusive reaction–diffusion systems

Study of weakly non-linear dynamics of a reaction–super-diffusion system near a Hopf bifurcation by means of fractional analogues of complex Ginzburg-Landau and Kuramoto-Sivashinsky equations is presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

非齐次线性方程组的快速迭代法

本文给出了一种解线性代数方程组的行正交化处理的新方法 ,它对任意初始向量 x0 ,利用格式x1 =x0 -∑ki=1u Tiuiu Tisi其中 ui=Ai-∑k- 1j=1Aiu Tjuju Tjsj,si=Aix0 -bi-∑i- 1j=1Aiu Tjuju Tjsj 可逐步逼近精确解 .这种方法在计算机上操作 ,则更显示出它的优越性 .