Finite-difference methods for solving the reaction-diffusion equations of a simple isothermal chemical system

Numerical methods are proposed for the numerical solution of a system of reaction-diffusion equations, which model chemical wave propagation. The reaction terms in this system of partial differential equations contain nonlinear expressions. Nevertheless, it is seen that the numerical solution is obtained by solving a linear algebraic system at each time step, as opposed to solving a nonlinear algebraic system, which is often required when integrating nonlinear partial differential equations. The development of each numerical method is made in the light of experience gained in solving the system of ordinary differential equations, which model the well-stirred analogue of the chemical system. The first-order numerical methods proposed for the solution of this initialvalue problem are characterized to be implicit. However, in each case it is seen that the numerical solution is obtained explicitly. In a series of numerical experiments, in which the ordinary differential equations are solved first of all, it is seen that the proposed methods have superior stability properties to those of the well-known, first-order, Euler method to which they are compared. Incorporating the proposed methods into the numerical solution of the partial differential equations is seen to lead to two economical and reliable methods, one sequential and one parallel, for solving the travelling-wave problem. © 1994 John Wiley & Sons, Inc.     

Finite-difference method for the Navier-Stokes equations in a variable domain with curved boundaries

A semi-implicit finite-difference scheme is proposed for solving the nonlinear viscous compressible Navier-Stokes equations. Coordinate transformations are constructed that yield a uniform mesh in the computational plane even though the physical domain under consideration is time-varying and curvilinear. The finite-difference scheme was tested using model examples.     

Finite-difference methods for solving loaded parabolic equations

Loaded partial differential equations are solved numerically. For illustrative purposes, a boundary value problem for a parabolic equation with various point loads is considered. By applying difference approximations, the problems are reduced to systems of algebraic equations of special structure, which are solved using a parametric representation involving solutions of auxiliary linear systems with tridiagonal matrices. Numerical results are presented and analyzed.     

Finite-difference method for singular nonlinear systems

This paper presents a method for solving nonlinear system with singular Jacobian at the solution. The convergence rate in the case of singularity deteriorates and one way to accelerate convergence is to form bordered system. A local algorithm, with finite-difference approximations, for forming and solving such system is proposed in this paper. To overcome the need that initial approximation has to be very close to the solution, we also propose a method which is a combination of descent method with finite-differences and local algorithm. Some numerical results obtained on relevant examples are presented.     

Finite-difference approximation of first-order partial differential-functional equations

We consider initial boundary-value problems of Dirichlet type for nonlinear equations. We give sufficient conditions for the convergence of a general class of one-step difference methods. We assume that the right-hand side of the equation satisfies an estimate of Perron type with respect to the functional argument.Published in Ukrainskii Matematicheskii Zhurnal, Vol. 46, No. 8, pp. 985–996, August, 1994.     

Finite-difference methods for solving the equations of magnetohydrodynamics on curvilinear moving grids

Translated from Chislennye Metody Resheniya Obratnykh Zadach Matematicheskoi Fiziki, pp. 75–86.     

Finite-difference schemes for solving multidimensional hyperbolic equations and their systems

A numerical algorithm for integrating second-order multidimensional hyperbolic equations and hyperbolic systems is described. Conditionally and unconditionally stable finite-difference schemes are constructed. The analysis of the schemes is based on the general regularization principle proposed by A.A. Samarskii.     

Symmetrization of the nonlinear system of gas dynamics equations

We describe a method for representing the nonlinear system of gas dynamics equations in quasilinear form with symmetric coefficient matrices and, moreover, with a positive definite matrix at the time derivative.     

A Newton-like method for nonlinear system of equations

Tanabe (1988) proposed a variation of the classical Newton method for solving nonlinear systems of equations, the so-called Centered Newton method. His idea was based on a deviation of the Newton direction towards a variety called “Central Variety”. In this paper we prove that the Centered Newton method is locally convergent and we present a globally convergent method based on the centered direction used by Tanabe. We show the effectiveness of our proposal for solving nonlinear system of equations and compare with the Newton method with line search.     

Nonmonotone filter DQMM method for the system of nonlinear equations

In this paper, we propose a nonmonotone filter Diagonalized Quasi-Newton Multiplier (DQMM) method for solving system of nonlinear equations. The system of nonlinear equations is transformed into a constrained nonlinear programming problem which is then solved by nonmonotone filter DQMM method. A nonmonotone criterion is used to speed up the convergence progress in some ill-conditioned cases. Under reasonable conditions, we give the global convergence properties. The numerical experiments are reported to show the effectiveness of the proposed algorithm.     

Finite-difference scheme for two-scale homogenized equations of one-dimensional motion of a thermoviscoelastic Voigt-type body

The Bakhvalov-Eglit two-scale homogenized equations are used to describe the motion of layered periodic compressible media with rapidly oscillating data. A new finite-difference scheme for a system of such equations is proposed and analyzed in the case of a thermoviscoelastic Voigt-type body. A priori estimates of solutions are derived for nonsmooth data. The existence and uniqueness of discrete solutions are established. A theorem is proved on the convergence of a subsequence of discrete solutions to a weak solution of the problem under study. Simultaneously, a new theorem on the existence of global weak solutions is deduced.     

Splitting schemes for the ocean dynamics equations

A splitting scheme in physical processes is proposed for a system of large-scale ocean dynamics equations. The convergence to an exact solution is proved for this scheme.     

Version of the elimination method for a system of partial differential equations

For a system of three first-order partial differential equations with three independent variables, we obtain sufficient conditions for one component of the solution to satisfy a third-order Bianchi equation. We also obtain conditions for the solvability of this system by quadratures.     

A nonmonotone filter trust region method for the system of nonlinear equations

In this paper, we present a nonmonotone filter trust region method to attack the system of nonlinear equations. The system of nonlinear equations is transformed into a constrained nonlinear programming problem at each step: some equations are treated as constraints while the others act as objective functions. Compared with the traditional filter strategies, our algorithm is flexible to accept trail steps by means of the nonmonotone filter technique. Moreover, the restoration phase is not needed so that the scale of the calculation is decreased in a certain degree. Global convergence is proven under some suitable conditions. Numerical experiments also show the efficiency of the algorithm.     

A new adaptive trust-region method for system of nonlinear equations

This study presents a new trust-region procedure to solve a system of nonlinear equations in several variables. The proposed approach combines an effective adaptive trust-region radius with a nonmonotone strategy, because it is believed that this combination can improve the efficiency and robustness of the trust-region framework. Indeed, it decreases the computational cost of the algorithm by decreasing the required number of subproblems to be solved. The global and the quadratic convergence of the proposed approach is proved without any nondegeneracy assumption of the exact Jacobian. Preliminary numerical results indicate the promising behavior of the new procedure to solve systems of nonlinear equations.     

A new solution method for state equations of nonlinear system

Along with the computation and analysis for nonlinear system being more and more involved in the fields such as automation control, electronic technique and electrical power system, the nonlinear theory has become quite a attractive field for academic research. In this paper, we derives the solutions for state equation of nonlinear system by using the inverse operator method (IOM) for the first time. The corresponding algorithm and the operator expression of the solutions is obtained. An actual computation example is given, giving a comparison between IOM and Runge-kutta method. It has been proved by our investigation that IOM has some distinct advantages over usual approximation methods in that it is computationally convenient, rapidly convergent, provides accurate solutions not requiring perturbation, linearization, or the massive computations inherent in discrietization methods such as finite differences. So the IOM provides an effective method for the solution of nonlinear system, is of potential application valuable in nonlinear computation.     

Piecewise spectral collocation method for system of Volterra integral equations

The main purpose of this paper is to investigate the piecewise spectral collocation method for system of Volterra integral equations. The provided convergence analysis shows that the presented method performs better than global spectral collocation method and piecewise polynomial collocation method. Numerical experiments are carried out to confirm these theoretical results.