Up-to boundary regularity for a singular perturbation problem of p-Laplacian type

In this paper we are interested in establishing up-to boundary uniform estimates for the one phase singular perturbation problem involving a nonlinear singular/degenerate elliptic operator. Our main result states: if Ω⊂Rn is a C1,α domain, for some 0<α<1 and uε verifies

     

The singular perturbation of boundary value problem for third-order nonlinear vector integro-differential equation and its application

In this paper, the singular perturbation of boundary value problem to a class of third-order nonlinear vector integro-differential equation is studied. Using the method of differential inequalities, under certain conditions, the existence of perturbed solution is proved, the uniformly valid asymptotic expansion for arbitrary order and the estimation of remainder term are given. Finally, the results are applied to study singularly perturbed boundary value problem to a nonlinear vector fourth-order differential equation. The existence of solution and its asymptotic estimation can be obtained conveniently.     

On a difference scheme of exponential type for a nonlinear singular perturbation problem

Summary A difference scheme of exponential type for solving a nonlinear singular perturbation problem is analysed. Although this scheme is not of monotone type, aL ¹ convergence result is obtained. Relations between this scheme and Engquist-Osher scheme are also discussed.     

Multigrid convergence for a singular perturbation problem

So far there has been no analysis of multigrid methods applied to singularly perturbed Dirichlet boundary-value problems. Only for periodic boundary conditions does the Fourier transformation (mode analysis) apply, and it is not obvious that the convergence results carry over to the Dirichlet case, since the eigenfunctions are quite different in the two cases. In this paper we prove a close relationship between multigrid convergence for the easily analysable case of periodic conditions and the convergence for the Dirichlet case.     

Orderh 2 method for a singular two-point boundary value problem

A method is described based on auniform mesh for the singular two-point boundary value problem:y+(/x)y+f(x, y)=0, 0<x1,y(0)=0,y(1)=A, and it is shown to be orderh ² convergent forall 1.     

A singular perturbation free boundary problem for elliptic equations in divergence form

In this paper we study the free boundary problem arising as a limit as ɛ → 0 of the singular perturbation problem , where A = A(x) is Holder continuous, β _ɛ converges to the Dirac delta δ₀. By studying some suitable level sets of u _ɛ, uniform geometric properties are obtained and show to hold for the free boundary of the limit function. A detailed analysis of the free boundary condition is also done. At last, using very recent results of Salsa and Ferrari, we prove that if A and Γ are Lipschitz continuous, the free boundary is a C ^1,γ surface around a.e. point on the free boundary.     

A fourth order method for a singular two-point boundary value problem

Recently, Chawla et al. described a second order finite difference method for the class of singular two-point boundary value problems:

Asymptotics of the eigenvalues of a boundary value problem for a vector singular differential equation

By analyzing a system of integro-differential equations of the Volterra-Stieltjes type, for large parameter values, we obtain asymptotic formulas for a linearly independent system of solutions of ordinary differential equations with generalized functions in coefficients. These solutions permit one to construct asymptotic formulas for the eigenvalues of a boundary value problem in the case of regular boundary conditions.     

A UNIFORM NUMERICAL METHOD FOR QUASILINEAR SINGULAR PERTURBATION PROBLEM WITH A TURNING POINT

A nonlinear difference scheme is given for solving a quasilinear siagularly perturbed two-point boundary value problem with a turning point. The method uses non-equidistant discretization meshes. The solution of the scheme is shown to be first order accurate in the discrete L^∞ norm, uniformly in the perturbation parameter.     

On a class of singular boundary value problems with singular perturbation

In this paper we investigate a class of singular second order differential equations with singular perturbation subject to three-point boundary value conditions, whose solution exhibits a couple of boundary layers at two endpoints. We first establish a lower–upper solutions theorem by using the Schauder fixed point theorem. By the asymptotic expansions and the lower–upper solutions theorem we obtain the existence, asymptotic estimates and uniqueness for the proposed problem. Several examples are given for illustrating our results.     

Fourth order algorithms for a semilinear singular perturbation problem

Fourth order finite-difference algorithms for a semilinear singularly perturbed reaction–diffusion problem are discussed and compared both theoretically and numerically. One of them is the method of Sun and Stynes (1995) which uses a piecewise equidistant discretization mesh of Shishkin type. Another one is a simplified version of Vulanović's method (1993), based on a discretization mesh of Bakhvalov type. It is shown that the Bakhvalov mesh produces much better numerical results. This revised version was published online in June 2006 with corrections to the Cover Date.     

On a singular perturbation problem in magnetohydrodynamics

Zusammenfassung Die Strömung einer zähen, inkompressiblen und elektrisch leitenden Flüssigkeit über einen rotationssymmetrischen Körper wird studiert mit Hilfe einer singulären Methode der Störungsrechnung. Eine asymptotische, im ganzen Strömungsfeld gültige Lösung wird gegeben für grosse Hartmann-ZahlenM.Die Resultate ergeben folgendes Strömungsbild: Zwei Totwasser-Bereiche von der LängeO (M) und der BreiteO (1) werden vor und nach dem Körper geformt. Sie sind begrenzt durch eine zylindrische Schubschicht, die vom grössten Durchmesser des Körpers aus parabolisch stromaufwärts und stromabwärts anwächst. In einer Entfernung der GrössenordnungO (M) geht diese Schubschicht in eine Wirbelstrasse über, die sich parabolisch ins Unendliche erstreckt. Die Einzelheiten des Strömungsbildes werden analytisch aufgezeigt. Die Wirbelstrasse wird mit derjenigen der klassischen Navier-Stokes-Theorie verglichen.     

A robust fitted operator finite difference method for a two-parameter singular perturbation problem1

We consider singularly perturbed two-point BVPs with two small parameters ? and μ multiplying the derivatives. It is pointed out in P.A. Farrel (Sufficient conditions for uniform convergence of a class of difference schemes for singular perturbation problems, IMA J. Numer. Anal. 7 (1987), pp. 459–472), that ‘in general, the exponentially fitted finite difference methods (EFFDMs) are more effective inside the layers. However, though these methods are uniformly convergent, they do not give fairly good approximations in the whole interval of interest’. In this paper, we study that the non-standard finite difference method (NSFDM) that we develop overcomes this weakness. Like EFFDMs, the NSFDM is also a method of fitted operator type. Secondly, unlike several earlier works (see, for example Gracia et al., Appl. Numer. Math. 56 (2006), pp. 962–980) where the authors use a combination of approaches in various regions, the method presented in this paper consists of just one scheme throughout the domain of interest. This is very important because it increases the possibilities of extending the approach both for higher dimensional and higher order problems. Combination of schemes usually suffers from the drawback that their selection is mostly based on the relative values of ? and μ, otherwise they fail to provide monotonic solutions. We also investigate a number of issues associated with a variety of NSFDMs and finally provide some comparative numerical results.     

Uniform convergence of discretization error for a singular perturbation problem

Cell-centered discretization of the convection-diffusion equation with large Péclet number Pe is analyzed, in the presence of a parabolic boundary layer. It is shown theoretically how, by suitable mesh refinement in the boundary layer, the accuracy can be made to be uniform in Pe, at the cost of a IogPe increase of the number of grid cells, in the case of upwind discretization. Numerical experiments are presented indicating that this can in practice also be achieved with a Pe-independent number of grid cells, both with upwind and central discretization, and with vertex-centered discretization. © 1996 John Wiley & Sons, Inc.     

On the perturbation determinants of a singular dissipative boundary value problem with finite transmission conditions

In this paper a singular dissipative boundary value problem with finite transmission conditions is investigated. Using Livšic’s theorem, it is proved that the system of all eigen and associated functions of this problem is complete in the Hilbert space.     

Iterative solution of a singular convection-diffusion perturbation problem

An iterative domain decomposition method is developed to solve a singular perturbation problem. The problem consists of a convection-diffusion equation with a discontinuous (piecewise-constant) diffusion coefficient, and the problem domain is decomposed into two subdomains, on each of which the coefficient is constant. After showing that the boundary value problem is well posed, we indicate a specific numerical implementation of the iterative technique that combines the finite element method on one subdomain with the method of matched asymptotic expansions on the other subdomain. This procedure extends work by Carlenzoli and Quarteroni, which was originally intended for a boundary layer problem with an outer region and an inner region. Our extension carries over to a problem where the domain consists of the outer and inner boundary layer regions plus a region in which the diffusion coefficient is constant and significant in magnitude. An unexpected benefit of our new implementation is its efficiency, which is due to the fact that at each iteration the problem needs to be solved explicitly only on one subdomain. It is only when the final approximation on the entire domain is desired that the matched asymptotic expansions approximation need be computed on the second subdomain. Two-dimensional convergence results and numerical results illustrating the method for a two-dimensional test problem are given.     

Iterative solution of a singular convection-diffusion perturbation problem

An iterative domain decomposition method is developed to solve a singular perturbation problem. The problem consists of a convection-diffusion equation with a discontinuous (piecewise-constant) diffusion coefficient, and the problem domain is decomposed into two subdomains, on each of which the coefficient is constant. After showing that the boundary value problem is well posed, we indicate a specific numerical implementation of the iterative technique that combines the finite element method on one subdomain with the method of matched asymptotic expansions on the other subdomain. This procedure extends work by Carlenzoli and Quarteroni, which was originally intended for a boundary layer problem with an outer region and an inner region. Our extension carries over to a problem where the domain consists of the outer and inner boundary layer regions plus a region in which the diffusion coefficient is constant and significant in magnitude. An unexpected benefit of our new implementation is its efficiency, which is due to the fact that at each iteration the problem needs to be solved explicitly only on one subdomain. It is only when the final approximation on the entire domain is desired that the matched asymptotic expansions approximation need be computed on the second subdomain. Two-dimensional convergence results and numerical results illustrating the method for a two-dimensional test problem are given.Received: February 12, 2004     

A modification of the invariant imbedding method for a singular boundary value problem

We consider a dynamically-consistent analytical model of a 3D topographic vortex. The model is governed by equations derived from the classical problem of the axisymmetric Taylor–Couette flow. Using linear expansions, these equations can be reduced to a differential sixth-order equation with variable coefficients. For this differential equation, we formulate a boundary value problem, which has a number of issues for numerical solving. To avoid these issues and find the eigenvalues and eigenfunctions of the boundary value problem, we suggest a modification of the invariant imbedding method (the Riccati equation method). In this paper, we show that such a modification is necessary since the boundary conditions possess singular matrices, which sufficiently complicate the derivation of the Riccati equation. We suggest algebraic manipulations, which permit the initial problem to be reduced to a problem with regular boundary conditions. Also, we propose a method for obtaining a numerical solution of the matrix Riccati equation by means of recurrence relations, which allow us to obtain a matrizer converging to the required eigenfunction. The suggested method is tested by calculating the corresponding eigenvalues and eigenfunctions, and then, by constructing fluid particle trajectories on the basis of the eigenfunctions.