A Spectral-Difference Method for Solving Two-Dimensional Vorticity Equations

We construct a spectral-difference schemes for solving two-dimensional vorticity equation with a single periodical boundary condition. The conservation, the generalized stability and the convergence are proved. Both steady and unsteady problems are considered.     

Fourier-Chebyshev Pseudospectral Method for Three-Dimensional Vorticity Equation

1.IntroductionInstudyingboundarylayers,flowspastsllddenlyheatedverticalplatesandotherrelatedproblems,we.havetoconsiderbilaterallyperiodicproblems.Thereareseveralwaystosolvethemnumerically.Forinstance,Murdok[1],Macaraeg[2]andBenyuGuo,Yue-shanXiong[31proposedspectral--differenceschemes,whileCanuto,Maday,Quarteroni[41andGuoBen--yu,CaoWeiMing[']developedspectral-finiteelementschemes.Buttheaccuracyofalltheseschemesisstilllimitedduetofinitedifferenceandfiniteelementapproximations,evenifthegenu…     

The Convergence of the Spectral Scheme for Solving Two-Dimensional Vorticity Equations

Much work has been done for the spectral scheme of the P.D.E. The author proposed a technique to prove the strict error estimation of the spectral scheme for the K.D.V.-Burgers equation. In this paper, the technique is generalized to two-dimensional vorticity equations. Under some conditions, the error estimation implies the convergence. The more smooth the solution of the vorticity equations, the more accurate the approximate solution.     

A Pseudospectral Method for Solving Navier-Stokes Equations

In this paper, we propose a new kind of pseudospectral schemes with a restraint operator to solve the periodic problem of Navier-Stokes equations. The generalized stability of the schemes is analysed and convergence is proved. Numerical results are presented also.     

高维广义BBM方程的Chebyshev拟谱方法

在非线性长波的研究中[1],提出并研究了BBM方程.由于这类方程在很多数学物理问题中出现,如双温热传导的冷却过程,液体在碎石中的渗流问题等,因而引起了人们的关注.这类方程的数值方法,已有许多工作,但主要是采用差分法和有限元法.[2]使用.Fourier谱方法讨论了一维广义BBM方程,我们在[3]中也用Fourier谱和拟谱方法讨论了高维广义BBM方程.然而对于非周期情况,Fourier谱方法无法使用.在     

多维广义SRLW方程的Chebyshev拟谱方法分析

考虑了一类多维的广义对称正则长波(SRLW)方程的齐次初边值问题Chebyshev拟谱逼近,构造了全离散的Chebyshev拟谱格式,给出了这种格式近似解的收敛性和最优误差估计。     

Multi-Symplectic Fourier Pseudospectral Method for a Higher Order Wave Equation of KdV Type

The higher order wave equation of KdV type, which describes many important physical phenomena, has been investigated widely in last several decades. In this work, multi-symplectic formulations for the higher order wave equation of KdV type are presented, and the local conservation laws are shown to correspond to certain well-known Hamiltonian functionals. The multi-symplectic discretization of each formulation is calculated by the multi-symplectic Fourier pseudospectral scheme. Numerical experiments are carried out, which verify the efficiency of the Fourier pseudospectral method.     

非线性对流-扩散方程的多区域拟谱方法

提出了非线性对流-扩散方程的多区域拟谱方法．在每个子区间上,该格式整体上按Legendre－Galerkin方法形成,但对于非线性项采用在 Legendre/Chebyshev－Gauss-Lobatto点上的配置法处理．通过选取适当的基函数,使得系数矩阵稀疏,并且可以并行计算,提高运算效率．给出了该方法的稳定性和收敛性分析,获得了按L2-模的最佳误差估计．最后给出单区域和多区域方法的数值算例,并加以比较．     

MKdV方程的多辛Fourier拟谱方法

基于谱微分矩阵方法,给出MKdV方程的多辛Fourier拟谱格式及其相应多辛离散守恒律,证明了它等价于通常的Fourier拟谱格式．数值结果表明,格式对于长时间计算具有稳定性与高精度．     

求解二维不可压缩Navier-Stokes方程的混合型微分求积法

微分求积法（ＤＱＭ）能以较少的网格点求得微分方程的高精度数值解,但采用单纯的微分求积法求解二维不可压缩Ｎａｖｉｅｒ＿Ｓｔｏｋｅｓ 方程时,只能对低雷诺数流动获得较好的数值解,当雷诺数较高时会导致数值解不收敛·　为此,提出了一种微分求积法与迎风差分法混合求解二维不可压缩Ｎａｖｉｅｒ＿Ｓｔｏｋｅｓ 方程的预估＿校正数值格式,用伪时间相关算法以较少的网格点获得了较高雷诺数流动的数值解·　作为算例,对１∶１ 和１∶２ 驱动方腔内的流动进行了计算,得到了较好的数值结果·     

The Linear Rational Pseudospectral Method for Boundary Value Problems

We consider the version of the pseudospectral method for solving boundary value problems which replaces the differential operator with a matrix constructed from the elementary differentiation matrices whose elements are the derivatives of the Lagrange fundamental polynomials at the collocation points. The iterative solution of the resulting system of equations then requires the recurrent application of that differentiation matrix. Since global polynomial interpolation on the interval only gives useful approximants for points which accumulate in the vicinity of the extremities, the matrix is ill-conditioned. To reduce this drawback, we use Kosloff and Tal-Ezer's suggestion to shift the collocation points closer to equidistant by a conformal map. However, instead of applying their change of variable setting, we extend to stationary equations the linear rational collocation method introduced in former work on partial differential equations. Numerically about as efficient, this does not require any new coding if one starts from an efficient program for the polynomial differentiation matrices.This revised version was published online in October 2005 with corrections to the Cover Date.     

Convergence Analysis for Pseudospectral Multidomain Approximations of Linear Advection Equations

Legendre and Chebyshev collocation schemes are proposed forthe numerical approximation of first order linear hyperbolicequations, by a domain decomposition procedure. Spectral convergenceestimates are provided both for Legendre and Chebyshev Gauss-Lobattonodes.     

层状二维流动的基本方程式

在很多海洋、大气等二维流动问题中所用的动力学方程往往沿用推广后的河流水力学方程或"纳维-斯托克斯方程"其中把湍流阻力项写成这样的方程式和湍流阻力项用到实际问题上去,无疑是存在着极大的局限性,而将导致矛盾百出.本文则从雷诺方程出发,把所有的物理量沿深度加以平均,求出平均以后的物理量所满足的运动方程,连续方程和扩散方程.     

The Blow-up of Solutions for Two-Dimensional Irrotational Compressible Euler Equations

For two-dimensional irrotational compressible Euler equations with initial data where that is a small perturbation from a constant state, we prove that the first-order derivatives of ρ, υ blow-up at the blow-up time, while ρ, υ remain continuous. In particular, in the irrotational case we prove S. Alinhac's statement. Project supported bythe Tianyuan Foundation of China and Lab. of Math. for Nonlinear Problems. Fudan. Univ.     

Optimal Control for Two-Dimensional Stochastic Navier-Stokes Equations

Loeb space methods are used to prove the existence of an optimal control for the two-dimensional stochastic Navier--Stokes equations in a variety of settings—including that of control based on digital observations of the evolution of the solution.     

Nonlinear Periodic Optimal Control: A Pseudospectral Fourier Approach

Abstract

A pseudospectral method for generating optimal trajectories of the class of periodic optimal control problems is proposed. The method consists of representing the solution of the periodic optimal control problem by an mth degree trigonometric interpolating polynomial, using Fourier nodes as grid points, and then discretizing the problem using the trapezoidal rule as the quadrature formula for smoothly differentiable periodic functions. The periodic optimal control problem is thereby transformed into an algebraic nonlinear programming problem. Due to its dynamic nature, the pseudospectral Fourier approach avoids many of the numerical difficulties typically encountered in solving standard periodic optimal control problems. An illustrative example is provided to demonstrate the applicability of the proposed method.     

The Linear Rational Pseudospectral Method with Preassigned Poles

We present a linear rational pseudospectral (collocation) method with preassigned poles for solving boundary value problems. It consists in attaching poles to the trial polynomial so as to make it a rational interpolant. Its convergence is proved by transforming the problem into an associated boundary value problem. Numerical examples demonstrate that the rational pseudospectral method is often more efficient than the polynomial method.     

守恒方程的Chebychev-Legendre拟谱粘性方法

给出了非线性守恒方程初边值问题的Chebychev-Legendre拟谱粘性法(CLSV). 文中,用补偿方法处理边界条件,而对高频部分使用粘性法,以恢复精度. 最后证明了在适当条件下,CLSV解收敛于唯一的熵解.     

A Pseudospectral Method for Fractional Optimal Control Problems

In this article, a direct pseudospectral method based on Lagrange interpolating functions with fractional power terms is used to solve the fractional optimal control problem. As most applied fractional problems have solutions in terms of the fractional power, using appropriate characteristic nodal-based functions with suitable power leads to a more accurate pseudospectral approximation of the solution. The Lagrange interpolating functions and their fractional derivatives belong to the Müntz space; such functions are employed to show that a relationship exists between the Karush–Kukn–Tucker conditions associated with nonlinear programming and the first optimal necessary conditions. Furthermore, the convergence of the method is investigated. The obtained numerical results are an indication of the behavior of the algorithm.