Home – Home – Jornals – Numerical Analysis and Applications 2017 number 3

A method for calculating the optimal consumption of the resource control of perturbed dynamic systems. This method includes both normal and singular solutions. According to the method proposed the problem is subdivided into three independent tasks: 1) a consideration of the effects of perturbations on the system; 2) computation of the optimal control structure; 3) computation of the switching moments of optimal control. A consideration of the effects of perturbations on the system and transfer to a non-zero final state are reduced to the transformation of the initial and final states of the systems. The structure calculation is based on the relation between deviations in the initial conditions of the conjugate systems and deviations of the phase trajectory at the completion instant. An iterative algorithm has been developed, its characteristics being considered. The results of modeling and numerical calculations are given.

By comparison with reliable experimental data in a wide range of pressure and temperature, it has been shown that the Redlich-Kwong equation of state appropriately reflects all the characteristics of the coefficient of compressibility, the throttling factor and the normalized difference of specific isobaric and isochoric heat capacities. It has been found that this equation corresponds to the inequalities required to ensure a set of equations of gas flow in pipelines to be hyperbolic.

The strict analytical solution to the eikonal equation for the plane wave refracted on convex and concave obtuse angles has been built. It has a shock line for the ray vector field and the first arrival times at the convex angle and a rarefaction cone with diffracted waves at the concave angle. This cone corresponds to the Keller diffraction cone in the geometric diffraction theory. The comparison of the first arrival times, the Hamilton-Jacoby equation times for downward waves and the conservation ray parameter equation times was made. It is shown that these times are equal only for pre-critical incident angles and are different for sub-critical angles. It is shown that the most energetic wave arrival times, which have dominant practical importance, are equal to the times calculated for the conservation ray parameter equation. The numerical algorithm proposed for these times calculation may be used for arbitrary velocity models.

In this paper, we study a priori error estimates for a finite volume element approximation of a nonlinear optimal control problem. The schemes use discretizations base on a finite volume method. For the variational inequality, we use a method of the variational discretization concept to obtain the control. Under some reasonable assumptions, we obtain some optimal order error estimates. The approximate order for the state, costate, and control variables is Oh²) or O(h²√|lnh|) in the sense of L²-norm or L^∞-norm. A numerical experiment is presented to test the theoretical results. Finally, we give some conclusions and future works.

This paper presents an algorithm for solving boundary value problems of the elasticity theory, suitable to solve contact problems and those whose scope of deformation contains thin layers of a medium. The solution is represented as a linear combination of subsidiary solutions and fundamental solutions to the Lame equations. Singular points of fundamental solutions of the Lame equations are located as an external layer of the deformation around the perimeter. Coefficients of the linear combination are determined by minimizing deviations of a linear combination from the boundary conditions. To minimize deviations, the conjugate gradient method is applied. Examples of calculations for mixed boundary conditions are presented.

In the polar coordinates, a discrete analog of the conjugate-operator model of the heat conduction problem preserves the structure of the original model. The difference scheme converges with the second order of accuracy for the cases of discontinuous parameters of the medium in the Fourier law and irregular grids. An efficient algorithm for solving the discrete conjugate-operator model in the case when the thermal conductivity tensor is a single operator.

This paper deals with the solution of a boundary value problem for the Darcy equation with a random hydraulic conductivity field. We use an approach based on the polynomial chaos expansion in the probability space of input data. We use the probabilistic collocation method to calculate the coefficients of the polynomial chaos expansion. A computational complexity of this algorithm is defined by the order of a polynomial chaos expansion and the number of terms in the Karhunen-Loève expansion. We calculate different Eulerian and Lagrangian statistical characteristics of the flow by the Monte Carlo and probabilistic collocation methods. Our calculations show a significant advantage of the probabilistic collocation method in comparison with the conventional direct Monte Carlo algorithm.

Based on a collocation technique, we introduce a unifying approach for deriving a family of multi-point numerical integrators with trigonometric coefficients for the numerical solution of periodic initial value problems. A practical 3-point numerical integrator is presented, whose coefficients are generalizations of classical linear multistep methods such that the coefficients are functions of an estimate of the angular frequency ω . The collocation technique yields a continuous method, from which the main and complementary methods are recovered and expressed as a block matrix finite difference formula which integrates a second order differential equation over non-overlapping intervals without predictors. Some properties of the numerical integrator are investigated and presented. Numerical examples are given to illustrate the accuracy of the method.