Existence of the Frontal Regime of Water-Steam Phase Transition in Hydrothermal Reservoirs

The problem of steam extraction from a water-saturated hydrothermal reservoir is considered. A parameter range in which there exists a noncontradictory solution of the problem with a sharp evaporation front is found. A critical curve distinguishing the region of existence of the frontal solution is constructed and an approximate solution of the problem corresponding to low evaporation surface velocities is found.     

Degenerate scale problem for plane elasticity in a multiply connected region with outer elliptic boundary

This paper investigates the degenerate scale problem for plane elasticity in a multiply connected region with an outer elliptic boundary. Inside the elliptic boundary, there are many voids with arbitrary configurations. The problem is studied on the relevant homogenous boundary integral equation. The suggested solution is derived from a solution of a relevant problem. It is found that the degenerate scale and the non-trivial solution along the elliptic boundary in the problem are same as in the case of a single elliptic contour without voids. The present study mainly depends on integrations of several integrals, which can be integrated in a closed form.     

Theoretical solution of the boundary problem of subsonic aerodynamics

A general theoretical solution of the boundary problem of aerodynamics of high subsonic velocities is presented. The solution of the partial differential equation for the velocity potential is carried out in the physical plane in streamline co-ordinates. The principle of the solution is the representation flow of a compressible fluid around a given profile to a hypothetical flow of an incompressible fluid around a different associated profile. In other words, the problem of compressible flow is transformed to the problem of incompressible flow, which can easily be solved. The results of this solution show very good agreement with solutions of other authors and with experiments.     

The torsion problem of a multilayered finite cylinder with the multiple interface cylindrical cracks

The torsion axisymmetric problem for a finite cylinder consisting of an arbitrary quantity of cylindrical coaxial layers is solved. Multiple cylindrical cracks with free of loading branches are situated on adjoining surfaces of the layers. The boundary problem is reduced to the system of integro-differential equations, its solution is found with the help of the orthogonal polynomials method. The novelty of the paper is in the construction of a solution for an arbitrary number of cylinder layers which allows the approximation of the initial problem for functionally graded materials by the problem for coaxial cylinders with jumplike changing elastic constants of the materials. Since the solution is built regardless of the number of layers (the elastic parameters of all layers are included in the constructed solution), one can refine an initial problem’s statement by increasing the number of layers. The stress intensity factors are found for an arbitrary number of cylindrical interface cracks in the multilayered cylinder of a finite length.     

Numerical nonlinear inverse problem of determining wall heat flux

The inverse problem of determining time-variable surface heat flux in a plane wall, with constant or temperature dependent thermal properties, is numerically studied. Different kinds of incident heat flux, including rectangular waveform, are assumed. The solution is numerically solved as a function estimation problem, so that no a priori information for the functional waveforms of the unknown heat flux is needed. In all cases, a solution in the form of a piece-wise function is used to approach the incident flux. Transient temperature measurements at the boundary, from the solution of the direct problem, served as the simulated experimental data needed as input for the inverse analysis. Both direct and inverse heat conduction problems are solved using the network simulation method. The solution is obtained step-by-step by minimising the classical functional that compares the above input data with those obtained from the solution of the inverse problem. A straight line of variable slope and length is used for each one of the stretches of the desired solution. The influence of random error, number of functional terms and the effect of sensor location are studied. In all cases, the results closely agree with the solution.     

Two-Valued Solutions in the Problem of Salt Precipitation during Groundwater Evaporation

The problem of the evaporation of groundwater containing a dissolved admixture is studied. It is shown that in the salt precipitation regime the solution is nonunique. At critical parameter values the solutions merge and in a certain region the solution of the problem disappears. The nonexistence of a solution corresponds to clogging of the pore space with precipitated salt.     

Spreading of a paraboloid elevation of liquid over a horizontal base

The literature contains studies [1–4] of the problem of the spreading of an axisymmetric elevation of ground water with conservation of the initial mass of the liquid and under the condition that some of the liquid remains in the previously occupied volume. The investigations used the Boussinesq equation with constant and discontinuous (at the point where ?h/?t = O, where h is the height of the elevation) permeability of the medium. For the first problem, there is an exact analytic solution of the type of an instantaneous source; the solution to the second problem was sought in the form of a self-similar solution of the second kind as an asymptotic solution for the corresponding Cauchy problem. In the present paper, the solution to the problem of the spreading of an axisymmetric elevation over a horizontal base is generalized to the case of an elevation having the shape of an elliptic paraboloid.     

Torsion of a square isotropic plate by forces applied at the corners and by distributed torques

We consider the classical problem of the theory of elastic plates, namely, the problem on the torsion of a square isotropic plane by forces applied at the corners. The traditional solution of this problem based on the classical theory of plates and Kirchhoff and Thomson–Tait transformations is compared with the solution obtained in the improved theory of plates and with experimental results. The solution, which does not exist in the classical theory of plates, of the problem on the torsion of a plate by torques uniformly distributed over the plate contour is presented as well.     

An exponentially fitted difference scheme for the hyperbolic-hyperbolic singularly perturbed initial-boundary value problem

In this paper we discuss,an initial-boundary value problem of hyperbolic type with firstderivative with respect to x.The asymptotic solution is constructed and its uniform validityis proved under weader compatibility conditions.Then we develop an exponentially fitteddifference scheme and establish discrete energy inequality.Finally,we prove that thesolution of difference problem uniformly converges to the solution of the original problem.     

Inplane deformation of a circular inhomogeneity with imperfect interface

The plane elastic problem of a circular inhomogeneity with an imperfect interface of spring-constant-type is reduced to the solution of a Somigliana dislocation problem, when the solution for the corresponding problem with a perfect interface is known. The Burger's vector of the Somigliana dislocation is determined so that its components satisfy two interfacial conditions involving the traction components of the corresponding problem with a perfect interface. Employing complex variables, a two-phase potential solution to the Somigliana dislocation inhomogeneity problem is developed for a general form of the Burger's vector. Detailed results are reported for a uniform eigenstrain in the inhomogeneity, and for a remote uniform heat flow in the matrix. In the latter case, the inhomogeneity behaves as a void, when it begins to slide.     

Stability of a cantilevered skew inhomogeneous plate in supersonic gas flow

This paper considers the vibrations of a skew inhomogeneous plate in gas flow. The plate is clamped in a certain section of one of its sides. Interaction of the flow with the plate is described using piston theory. The problem solution is based on the Hamilton’s variational principle and finite element method. The calculation results are compared with known data of theoretical studies and experiments. For the inhomogeneous plate, similarity parameters were established for the problem, which, in practically important cases, appears to be self-similar for one of the similarity parameters. This allows one to reduce the solution of this problem to the solution of an algebraic eigenvalue problem.     

Symmetry groups and similarity solutions for a free convective boundary-layer problem

The free convective boundary-layer problem due to the motion of an elastic surface into an electrically conducting fluid is studied with group-theoretical methods. The symmetry groups admitted by the corresponding boundary value problem are obtained. Particular attention is paid on the group of scaling which provides the similarity solution of the problem. Also, the admissible form of the data, in order to be conformed to the obtained symmetries, is provided. Finally, with the use of the entailed similarity solution the problem is transformed into a boundary value problem of ODEs and is solved numerically.     

Form of a free surface during steady flow of a capillary fluid in a rectangular channel

The two-dimensional problem of the form of a free surface of an ideal incompressible fluid during steady flow from a rectangular channel through a thin slot with simultaneous uniform delivery of fluid through the side walls is examined. Forces of gravity and surface tension are taken into account. The nonlinear problem of the simultaneous determination of the free surface and velocity field of the fluid is solved by the iteration method. Convergence of the iterations to the solution of the problem for small values of the parameters is investigated. The solution of the linearized problem is obtained in a closed form for a small depth of the discharge and small width of the channel, which is compared with the solution of the problem in a complete formulation. Graphs of the free surface of the fluid for different values of the parameters, obtained as a result of numerical solution of the nonlinear problem, are presented.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 67–75, January–February, 1977.     

Analytical solution of basic equations set of atmospheric motion

On condition that the basic equations set of atmospheric motion possesses the best stability in the smooth function classes, the structure of solution space for local analytical solution is discussed, by which the third-class initial value problem with typicality and application is analyzed. The calculational method and concrete expressions of analytical solution about the well-posed initial value problem of the third kind are given in the analytic function classes. Near an appointed point, the relevant theoretical and computational problems about analytical solution of initial value problem are solved completely in the meaning of local solution. Moreover, for other type of problems for determining solution, the computational method and process of their stable analytical solution can be obtained in a similar way given in this paper.     

Perturbation solution to heat conduction in melting or solidification with heat generation

The Stefan problem involving a source term is considered in this technical note. As an example, planar solidification with time-dependent heat generation in a semi-infinite plane is solved by use of a perturbation technique. The perturbation solution is validated by reducing the problem to the case without heat generation whose exact solution is available. An application to the case with constant heat generation is presented, for which a closed-form solution is obtained. The effects of heat generation and Stefan number on the evolution of solidification are examined using the perturbation solution.     

Mixed boundary value problems for a penny-shaped cut

The axially symmetric problem for a penny-shaped cut is solved in the case the displacements are prescribed on its upper surface and stresses on its lower surface. The solution is achieved by using integral transforms along with certain representations that reduce the general problem to the solution of uncoupled Hilbert problems. For polynomial loadings the Hilbert problems can be solved exactly by methods given by Muskhelishvili. As in the related plane problem two singularities at the edge of the disc are noted in the solution.     

On the long-time limit of the Garvin–Alterman–Loewenthal solution for a buried blast load

The Garvin–Alterman–Loewenthal solution refers to the problem of a line blast load suddenly applied in the interior of an elastic half-space. It is expected that the long-time asymptotic limit of this solution should be equal to the solution of a related static problem. This expectation is justified here. First, the solution of the static problem is constructed. Then, the asymptotic limit of the transient problem is found, correcting previously published results.     

Pressure distribution in the neighborhood of a growing fracture with a constant wedge force

Exact solutions of the problem of the pressure field in the neighborhood of a hydraulic fracture developing in accordance with a square root law in a permeable porous medium with a constant wedge force acting on the fracture edges are constructed. A particular case admitting a self-similar formulation and an exact solution and, as a result, the fairly complete investigation, is considered. The solution constructed holds for an arbitrary self-similar pressure distribution over the fracture edges. The problem considered reduces to the solution of a mixed boundary-value problem for the Helmholtz equation. The solution found can be useful both in itself and for testing more universal numerical algorithms.     

On the diffusion of load from a stiffener into an infinite wedge-shaped plate

Summary The stress-distribution in a wedge-shaped plate with a stiffener upon one of the edges is considered. The stiffener is loaded by an axial force. The problem leads to the solution of a biharmonic equation with one mixed boundary condition. The problem is reduced to the standard problem of the stress-distribution in a wedge. The reduction has been executed by the solution of a difference equation for the transform of the shear-stress along the stiffened edge. For this solution we give two representations: one by means of an infinite product and one by means of an integral. Full discussion is given on asymptotic behaviour and on the numerical aspects.     

The existence of the solution for linear complementary problem

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