Numerical simulation of LI-ION battery thermo-electrochemical processes
Количество страниц: 14 с.
We present a numerical simulation of thermo-electrochemical processes of a Li-ion battery. Mathematical model of thermo-electrochemical processes is described on a microscopic scale and contains nonlinear equations for concentration, potential and temperature. A Li-ion battery consists of three subdomains: two electrodes and the electrolyte. On the interface of electrodes and electrolyte there are Lithium ions intercalation and deintercalation processes which are described by the Butler—Volmer nonlinear equation. The main problem of numerical implementation is the discontinuity of concentration and potential at the interface of the subdomains. To take into account the discontinuity, we use mixed finite elements in spatial approximation of a coupled system: discontinuous Galerkin elements for concentration and potential and continuous Galerkin elements for temperature. The time approximation is performed using a fully implicit scheme. The nonlinear system of equations obtained by approximation is solved by the Newton method.
Захаров, П. Е. Численное моделирование термо-электрохимических процессов в LI-ION аккумуляторах / П. Е. Захаров, М. А. Никифорова // Математические заметки СВФУ. - 2018. - Т. 25, N 4 (100), октябрь-декабрь. - C. 102-114.
Conservative difference scheme for filtering problems in fractured media
Количество страниц: 18 с.
We consider filtration problems in the fractured media that are necessary when modeling the processes of extracting hydrocarbons from unconventional reservoirs, geothermal fields development, underground disposal of radioactive waste in aquifers, etc. Fracture networks in such oil pools can exist on different scales and differ in the nature of their occurrence. We discuss a mathematical model of fluid filtration in fractured porous media described by coupled equations of mixed dimension with assigning of a special flow function. The problem approximation is constructed through the finite difference method on structured grids using the embedded fracture model, which makes possible creating grids for the porous medium matrix independently of the fracture network grid. The construction of a conservative difference scheme is given for the matrix of porous medium with the use of an integro-interpolation method and generalized for coupled equations describing mathematical models of multicontinuum with hierarchical representation of fracture networks. The results of the numerical implementation of the two-dimensional model problem are presented.
Васильева, М. В. Консервативная разностная схема для задач фильтрации в трещиноватых средах // Математические заметки СВФУ. — 2018. — Т. 25, N 4 (100), октябрь-декабрь. — C. 84-101.
On solvability of nonlocal boundary value problems for integro-differential equations
Количество страниц: 10 с.
We study the solvability of the initial-boundary value problem for linear integro-differential equations with a lateral boundary condition correlating values of the solution or its conormal derivative with values of some integral operator on the solution. We prove existence and uniqueness theorems for regular solutions. Recently, nonlocal boundary value problems for parabolic and hyperbolic equations with integral conditions on the lateral boundary are intensively studied, primarily in the classical case of secondand fourth-order equations. The systematic study of nonlocal boundary value problems, the problems of finding periodic solutions to elliptic equations, began in the article by A. V. Bitsadze and A. A. Samarskii (1969). A great contribution to the development of the theory of nonlocal problems for differential equations of various classes was made by A. L. Skubachevsky (1997) and A. M. Nakhushev (2006, 2012).
Попов, Н. С. О разрешимости нелокальных краевых задач для интегродифференциальных уравнений / Н. С. Попов // Математические заметки СВФУ. — 2018. — Т. 25, N 4 (100), октябрь-декабрь. — C. 74-83.
On the density of a special class of Lizorkin functions in a weighted lebesgue space L (gamma) p
Количество страниц: 14 с.
We study the class of test functions constructed on the principle of Lizorkin spaces by means of mixed Fourier-Kipriyanov-Katrakhov transform. Initially, such classes of functions, constructed on the basis of a mixed Fourier-Bessel transform, were investigated by L. N. Lyakhov. The spaces introduced by him could not take into account “odd” orders of singular derivatives. But the latter appeared to be fundamentally necessary in the problems of determining the fundamental solutions of differential equations (ordinary and in partial derivatives). The integral Kipriyanov-Katrakhov transform (belonging to the class of Bessel transforms) is adapted to work with singular differential operators of the type where k takes values 0 or 1, is a singular differential Bessel operator and the order of differentiation is 2m. The spaces of the basic functions that represent the images of the mixed Fourier-Kipriyanov-Katrakhov transform of functions vanishing at the origin and infinity are considered in this paper. We study the possibility of approximating functions from weighted Lebesgue classes with power weight namely, the density theorem in the Lebesgue function space.
Половинкина, М. В. О плотности специального класса функций Лизоркина в весовом лебеговом пространстве L (gamma) p / М. В. Половинкина, С. А. Рощупкин // Математические заметки СВФУ. — 2018. — Т. 25, N 4 (100), октябрь-декабрь. — С. 60-73.
On the first mixed problem in banach spaces for degenerate parabolic equations with changing time direction
Количество страниц: 16 с.
The article is devoted to studying one of the sections of nonclassical differential equations, namely, matters concerned with solvability of parabolic equations with changing second-order time direction. As is known, in ordinary boundary-value problems for strictly parabolic equations, the smoothness of the initial and boundary conditions completely ensures that the solutions belong to the Holder spaces, but in the case of equations with changing time direction, the smoothness of the initial and boundary conditions does not ensure that the solutions belong to these spaces. S.A. Tersenov (for a model parabolic equation with changing time direction) and S.G. Pyatkov (for a more general second-order equation) obtained the necessary and sufficient conditions for solvability of the corresponding mixed problems in Holder spaces. In so doing, they always assumed the initial and boundary conditions being equal to zero. Cases in which the initial and boundary conditions belong to Banach spaces are considered. The functional spaces in which the solutions must be sought are introduced. Relevant a priori estimates, which make it possible to obtain the solvability conditions for these problems, are obtained. The properties of the obtained solutions have been studied. In particular, the equivalence of the Riesz and Littlewood-Paley conditions similar to the conditions for solutions of strictly elliptic and strictly parabolic second order equations is established. A unique solvability of the first mixed problem with boundary and initial functions from the Banach space has been proved.
Петрушко, И. М. О первой смешанной задаче в банаховых пространствах для вырождающихся уравнений с меняющимся направлением времени / И. М. Петрушко, М. И. Петрушко // Математические заметки СВФУ. — 2018. — Т. 25, N 4 (100), октябрь-декабрь. — С. 45-59.
Boundary value problems for twice degenerate differential equations with multiple characteristics
Количество страниц: 12 с.
Кожанов, А. И. Краевые задачи для дважды вырождающегося дифференциального уравнения с кратными характеристиками / А. И. Кожанов, О. С. Зикиров // Математические заметки СВФУ. — 2018. — Т. 25, N 4 (100), октябрь-декабрь. — С. 34-44.
On existence of boundary and initial values for degenerate parabolic equations in stellar domains
Количество страниц: 20 с.
We establish the necessary and sufficient conditions for the solution of the second-order parabolic equation in a stellar domain with a lateral boundary in the class degenerate on the boundary of the domain, to have an average limit on the lateral surface of the cylindrical domain and the limit in the mean on its lower base. Also, we study the unique solvability of the first mixed problem for such equations in the case when the boundary and initial functions belong to spaces of the type. The closest to the questions under consideration are the theorems of Riesz and Littlewood and Paley, in which criteria are given for the limit values in p > 1, of functions analytic in the unit disk. Further development of this topic for uniformly elliptic equations was obtained in the works V. P. Mikhailov and A. K. Gushchin. The boundary smoothness condition can be weakened, as was shown by I. M. Petrushko. Under the weakest restrictions on the smoothness of the boundary (and on the coefficients of the equation), the criteria for the existence of a boundary value were established in by A. K. Gushchin. In this case, all directions of the acceptance of boundary values for uniformly elliptic equations turn out to be equal, the solution has the property similar to the property of continuity with respect to the set of variables. In the case of degeneracy of the equation on the boundary of the domain, when the directions are not equal, the situation is more complicated. In this case, the formulation of the first boundary value problem is determined by the type of degeneracy. When the values of the corresponding quadratic form of the degenerate elliptic equation on the normal vector are different from zero (Tricomi type degeneracy), the Dirichlet problem is well-posed and the properties of such degenerate equations are very close to the properties of uniformly elliptic equations. In particular, in this situation analogues of the Riesz and Littlewood-Paley theorems are valid.
Капицына, Т. В. О существовании граничных и начальных значений для вырождающихся параболических уравнений в звездных областях / Т. В. Капицына // Математические заметки СВФУ. — 2018. — Т. 25, N 4 (100), октябрь-декабрь. — С. 15-33.
Some classes of inverse problems for mixed type equations of second order
Количество страниц: 12 с.
In the Sobolev spaces, we consider the well-posedness questions for the inverse problem of recovering the source function of a mixed type equation of second order. The overdetermination conditions are the values of a solution on a collection of planes of dimension n − 1. The unknowns occurring in the right-hand side depend on time and n − 1 unknown space variables. Under certain natural conditions on the data of the problem, we obtain existence and uniqueness theorems for generalized solutions to this problem. The conditions on the data almost coincide with those ensuring solvability of the direct problem. The parameter continuation method and a priori estimates are used to validate the results. The method allows us to generalize the results to the case of smoother data and regular solutions.
Джамалов, С. З. Некоторые классы обратных задач для уравнений смешанного типа второго порядка / С. З. Джамалов, С. Г. Пятков // Математические заметки СВФУ. — 2018. — Т. 25, N 4 (100), октябрь-декабрь. — С. 3-14.
Evaluation of the radiation coefficient effect in total heat transfer between network pipeline and water pipes in joint installation
Количество страниц: 6 с.
- Математика. Естественные науки > Математика,
- НАУКА > МАТЕМАТИКА. ЕСТЕСТВЕННЫЕ НАУКИ > Математика,
- Прикладные науки. Медицина. Техника. Сельское хозяйство > Инженерное дело. Техника в целом,
- НАУКА > МАТЕМАТИКА. ЕСТЕСТВЕННЫЕ НАУКИ > Физика,
- НАУКА > ПРИКЛАДНЫЕ НАУКИ. МЕДИЦИНА. ТЕХНИКА. СЕЛЬСКОЕ ХОЗЯЙСТВО > Инженерное дело. Техника в целом.
This paper considers a mathematical model of joint laying of water pipeline networks and district heat networks. The purpose of the work is to study the effect of radiation on the process of complex heat exchange taking place in the housing insulation between structural elements. The results of mathematical simulation of the heat loss taking into account the radiant component are given. When calculating the heat flows which are lost in the pipeline through thermal insulation at transporting the coolant, the heat transfer process is usually considered by means of conduction and convection. The radiant component is neglected in most cases. The influence of heat transfer by radiation and convection is particularly noticeable using thermal insulation products with large pores and air gaps. A ground configuration of a pipe line and water pipe line laid in a joint thermal insulation made of mineral wool is considered. When laying joint pipelines, complex radiative heat transfer occurs. It consists, for each one of these pipelines, of radiation reflected from the other pipeline and self-radiation. A non-stationary temperature field of the structure, consisting of two parallel stacked pipes with different diameters lying in a joint insulating structure made of mineral wool, is calculated. The construction elements exchange heat with each other and the environment by convection and radiation.
Степанов, А. В. Оценка влияния лучистой составляющей на сложный теплообмен между сетевым трубопроводом и водопроводом при совместной прокладке / А. В. Степанова, Г. Н. Егорова // Наука и образование. — 2017. — N 4 (88), октябрь-декабрь. — С. 93-98.
Количество страниц: 5 с.
The influence of solar radiation in the temperature field of the permafrost massif on horizontal surfaces is considered taking into account changes in solar radiation during the day. A mathematical process model is constructed and implemented based on a Stefan type problem. The calculation of the number of freezing-thawing cycles in the spring and autumn for the conditions of Central Yakutia was made.
Расчет количества циклов замерзания-оттаивания породного массива для условий центральной Якутии на горизонтальных поверхностях / В. И. Слепцов, С. Д. Мордовской, Е. Е. Петров. – Текст : непосредственный // Горный информационно-аналитический бюллетень. – 2012. – N 9. – C. 99-114.