Nonuniform FDM for Poisson-Type Equations on a Disk with Singular Solutions

We are concerned with the Dirichlet boundary value problem of Poisson-type equations on a disk. Matsunaga and Yamamoto [8 N. Matsunaga and T. Yamamoto ( 1999 ). Convergence of Swartztrauber–Sweet's approximation for the Poisson-type equation on a disk . Numer. Funct. Anal. Optimz. 20 : 917 – 928 .[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]] proved that if the exact solution u is very smooth over the closure of the disk, then the approximate solution by the Swartztrauber–Sweet scheme with uniform partition is second order accurate. In this article, it is assumed that the exact solution performs singular properties such that its derivatives go to infinity at the boundary of the disk. We use a stretching polynomial-like function with a parameter to construct a local grid refinement and consider the Swartztrauber–Sweet scheme over the non-uniform partition. The effects of the parameter are analyzed completely by carrying out convergence analysis and numerical results show that there exists an optimal value for the parameter to have a best approximated solution.     

广义神经传播方程的非协调变网格有限元方法

本文将Crouzeix-Raviart型各向异性非协调线性三角形元应用到广义神经传播方程,建立了其Crank-Nicolson变网格逼近格式.同时,直接利用插值技巧和单元的特殊性质给出了相应的收敛性分析和最优误差估计.     

Supraconvergence of a finite difference scheme for solutions in Hs(0, L)

^** Email: silvia{at}mat.uc.pt^*** Email: ferreira{at}mat.uc.pt^**** Email: grigo{at}math.tu-berlin.de In this paper we study the convergence of a centred finite differencescheme on a non-uniform mesh for a 1D elliptic problem subjectto general boundary conditions. On a non-uniform mesh, the schemeis, in general, only first-order consistent. Nevertheless, weprove for s (1/2, 2] order O(h^s)-convergence of solution andgradient if the exact solution is in the Sobolev space H^1+s(0,L), i.e. the so-called supraconvergence of the method. It isshown that the scheme is equivalent to a fully discrete linearfinite-element method and the obtained convergence order isthen a superconvergence result for the gradient. Numerical examplesillustrate the performance of the method and support the convergenceresult.     

A Finite Difference Scheme for Blow-Up Solutions of Nonlinear Wave Equations

<正>We consider a finite difference scheme for a nonlinear wave equation,whose solutions may lose their smoothness in finite time,i.e.,blow up in finite time.In order to numerically reproduce blow-up solutions,we propose a rule for a time-stepping, which is a variant of what was successfully used in the case of nonlinear parabolic equations.A numerical blow-up time is defined and is proved to converge,under a certain hypothesis,to the real blow-up time as the grid size tends to zero.     

分布控制中一类半线性抛物方程的差分格式

本文讨论了在分布控制中出现的一类半线性抛物方程的有限差分方法.构造了一个线性化隐式差分格式.证明了差分格式解的存在唯一性、收敛性和无条件稳定性.并给出了L2和L∞范数意义下的收敛阶数为O(h2 τ2).数值例子验证了理论分析结果.     

一类半线性抛物型方程的紧差分格式

本文构造了一类半线性抛物方程初边值问题的紧差分格式．利用离散能量估计证明了差分格式解的存在唯一性、收敛性和无条件稳定性，并给出了在离散L^∞模意义下收敛阶数为O（h^4＋τ^2）．数值例子验证了理论分析结果。     

Partition of Unity for a Class of Nonlinear Parabolic Equation on Overlapping Non-Matching Grids

A class of nonlinear parabolic equation on a polygonal domain Ω  R2 is inves- tigated in this paper. We introduce a finite element method on overlapping non-matching grids for the nonlinear parabolic equation based on the partition of unity method. We give the construction and convergence analysis for the semi-discrete and the fully discrete finite element methods. Moreover, we prove that the error of the discrete variational problem has good approximation properties. Our results are valid for any spatial dimensions. A numerical example to illustrate the theoretical results is also given.     

A Finite Volume Implicit Euler Scheme for the Linearized Shallow Water Equations: Stability and Convergence

The linearized shallow water equations are discretized in space by a finite volume method and in time by an implicit Euler scheme. Stability and convergence of the scheme are proved.     

Numerical Locking Problems for Hyperbolic Equations

We investigate a time-dependent model concerning the “locking phenomenon,” namely a model for three-dimensional clamped curved rods. We show that the convergence of the numerical schemes is independent of the discretization parameters and the thickness of the rod. We present corresponding numerical experiments.     

在非均匀网格上解椭圆—双曲型偏微分方程奇异摄动问题

本文考察了椭圆一双曲型偏微分方程奇异摄动问题(1.1),证明了迎风差分格式在一特殊的非均匀网格上是一阶一致收敛的.最后给出了一些数值结果.     

A Finite Volume Scheme for Savage-Hutter Equations on Unstructured Grids

A Godunov-type finite volume scheme on unstructured grids is proposed to numerically solve the Savage-Hutter equations in curvilinear coordinate. We show the direct observation that the model isn't a Galilean invariant system. At the cell boundary, the modified Harten-Lax-van Leer (HLL) approximate Riemann solver is adopted to calculate the numerical flux. The modified HLL flux is not troubled by the lack of Galilean invariance of the model and it is helpful to handle discontinuities at free interface. Rigidly the system is not always a hyperbolic system due to the dependence of flux on the velocity gradient. Even so, our numerical results still show quite good agreements with reference solutions. The simulations for granular avalanche flows with shock waves indicate that the scheme is applicable.     

自然对流换热问题基于混合元法的差分格式及其数值模拟

研究自然对流换热问题,通过对于空间变量采用有限元离散而对于时间变量用差分离散,导出一种基于混合有限元法的最低阶的差分格式,这种格式可以同时求出流体的速度、温度和压力的数值解,并给出了模拟方腔流的自然换热的数值例子。     

A Finite Difference Scheme for a Semiconductor Device Problem on Grids with Local Refinement in Time and Space

The momentary state of a semiconductor device is described by a system of three nonlinear partial differential equations. A finite difference scheme for simulating transient behaviors of a semiconductor device on grids with local refinement in time and space is constructed and studied. Error analysis is presented and is illustrated by numerical examples.     

Numerical Locking Problems for Parabolic Equations

We investigate the time evolution of a previous elliptic model. We study a parabolic model concerning the “numerical locking” phenomenon, namely a model for three-dimensional curved rods clamped at the endpoints. We show that the convergence of the numerical schemes is independent of the discretization parameters and the thickness of the rod. We present corresponding numerical experiments and we make a comparison with the results obtained for the hyperbolic model.     

关于一类HJ方程的Godunov通量的一点注记

本文对[1]中关于一类HJ方程的Godunov通量的命题作出改进,并给出新的证明.     

高阶椭圆型偏微分方程奇异摄动问题一致收敛差分格式

本文,我们讨论了一类高阶椭圆型偏微分方程奇异摄动问题。给出了连续问题解的先验估计。另外,我们还提供了一种数值求解该类问题的指数型差分格式。最后,证明了差分问题的解在能量范数意义下关于小参数一致收敛到连续问题的解。     

Convergence Analysis of the Shortley-Weller Method on Refinement Grids for Elliptic Equations with Singularities

In this article, we consider the convergence problem of the Shortley-Weller method on refinement grids applied to elliptic partial differential equations. The refinement uses polynomial and exponential stretching functions for Dirichlet boundary value problems in a bounded domain Ω whose solutions have singular derivatives near a part or the whole of the boundary of Ω. In the case where Ω is the unit square, it is shown that the methods are convergent and the convergence can be accelerated by varying parameters in the stretching functions. Numerical examples are given to illustrate how the effect on the stretching functions depends upon the choice of parameters.     

解三维热传导方程的一种高精度的显格式

对解三维热传导方程利用待定参数方法构造出一种精度O(Δt2+Δx4+Δy4+Δz4)的高精度易于计算的显式差分格式,并给出了其稳定性,通过数值例子可见其精度较其它方法提高2～3位有效数字。     

一类广义的Kdv方程的显式差分解

本文考察一类具耗散的广义KdV方程组■ (gradφ(■))_x ■_(xxx)-α■_(xx) γ■ =■(x,t,■)的周期初值问题的显式差分格式．利用有界延拓法证明了该差分格式的收敛性与稳定性,并给出了算法和数值例子．