Faedo-Galerkin Method Research Articles

Cahn-Hilliard equation with capillarity in actual deforming configurations

<p style='text-indent:20px;'>The diffusion driven by the gradient of the chemical potential (by the Fick/Darcy law) in deforming continua at large strains is formulated in the reference configuration with both the Fick/Darcy law and the capillarity (i.e. concentration gradient) term considered at the actual configurations deforming in time. Static situations are analysed by the direct method. Evolution (dynamical) problems are treated by the Faedo-Galerkin method, the actual capillarity giving rise to various new terms as e.g. the Korteweg-like stress and analytical difficulties related to them. Some other models (namely plasticity at small elastic strains or damage) with gradients at an actual configuration allow for similar models and analysis.

Existence and exponential decay of the Dirichlet problem for a nonlinear wave equation with the Balakrishnan–Taylor term*

In this paper, we consider the Dirichlet problem for a nonlinear wave equation with Balakrishnan–Taylor term. We establish the local existence is established by the linearization method together with the Faedo–Galerkin method. Next, we prove an exponential energy decay result by suitable Lyapunov functionals.

A Novel Decay Rate for a Coupled System of Nonlinear Viscoelastic Wave Equations

The main goal of the present paper is to study the existence, uniqueness and behavior of a solution for a coupled system of nonlinear viscoelastic wave equations with the presence of weak and strong damping terms. Owing to the Faedo-Galerkin method combined with the contraction mapping theorem, we established a local existence in [ 0 , T ] . The local solution was made global in time by using appropriate a priori energy estimates. The key to obtaining a novel decay rate is the convexity of the function χ , under the special condition of the initial energy E ( 0 ) . The condition of the weights of weak and strong damping has a fundamental role in the proof. The existence of both three different damping mechanisms and strong nonlinear sources make the paper very interesting from a mathematics point of view, especially when it comes to unbounded spaces such as R n .

Strong Solutions of the Incompressible Navier–Stokes–Voigt Model

This paper deals with an initial-boundary value problem for the Navier–Stokes–Voigt equations describing unsteady flows of an incompressible non-Newtonian fluid. We give the strong formulation of this problem as a nonlinear evolutionary equation in Sobolev spaces. Using the Faedo–Galerkin method with a special basis of eigenfunctions of the Stokes operator, we construct a global-in-time strong solution, which is unique in both two-dimensional and three-dimensional domains. We also study the long-time asymptotic behavior of the velocity field under the assumption that the external forces field is conservative.

Global existence of weak solutions to 3D compressible primitive equations with degenerate viscosity

In this paper, we investigate the compressible primitive equations (CPEs) with density-dependent viscosity for large initial data. The CPE model can be derived from the 3D compressible and anisotropic Navier–Stokes equations by hydrostatic approximation. Motivated by the work of Vasseur and Yu [SIAM J. Math. Anal. 48, 1489–1511 (2016); Invent. Math. 206, 935–974 (2016)], in which the global existence of weak solutions to the compressible Navier–Stokes equations with degenerate viscosity was obtained, we construct approximate solutions and prove the global existence of weak solutions to the CPE in this paper. In our proof, we first present the vertical velocity as a function of density and horizontal velocity, which plays a role in using the Faedo–Galerkin method to obtain the global existence of the approximate solutions. Then, we obtain the key estimates of lower bound of the density, the Bresch–Desjardins entropy on the approximate solutions. Finally, we apply compactness arguments to obtain global existence of weak solutions by vanishing the parameters in our approximate system step-by-step.

On the fractional version of Leibniz rule

AbstractThis manuscript is dedicated to prove a new inequality that involves an important case of Leibniz rule regarding Riemann–Liouville and Caputo fractional derivatives of order . In the context of partial differential equations, the aforesaid inequality allows us to address the Faedo–Galerkin method to study several kinds of partial differential equations with fractional derivative in the time variable; particularly, we apply these ideas to prove the existence and uniqueness of solution to the fractional version of the 2D unsteady Stokes equations in bounded domains.

Countable stability of a weak solution of a parabolic differential-difference system with distributed parameters on the graph

The article proposes an analog of E. Rothe’s method (semi-discretization with respect to the time variable) for construction convergent different schemes when analyzing the countable stability of a weak solution of an initial boundary value problem of the parabolic type with distributed parameters on a graph in the class of summable functions. The proposed method leads to the study of the input initial boundary value problem to analyze the boundary value problem in a weak setting for elliptical type equations with distributed parameters on the graph. By virtue of the specifics of this method, the stability of a weak solution is understood in terms of the spectral criterion of stability (Neumann’s countable stability), which establishes the stability of the solution with respect to each harmonic of the generalized Fourier series of a weak solution or a segment of this series. Thus, there is another possibility indicated, in addition to the Faedo—Galerkin method, for constructing approaches to the desired solution of the initial boundary value problem, to analyze its stability and the way to prove the theorem of the existence of a weak solution to the input problem. The approach is applied to finding sufficient conditions for the countable stability of weak solutions to other initial boundary value problems with more general boundary conditions — in which elliptical equations are considered with the boundary conditions of the second or third type. Further analysis is possible to find the conditions under which Lyapunov stability is established. The approach can be used to analyze the optimal control problems, as well as the problems of stabilization and stability of differential systems with delay. Presented method of finite difference opens new ways for approximating the states of a parabolic system, analyzing their stability in the numerical implementation and algorithmization of optimal control problems.

Uniform stability of transmission of wave-plate equations with source on Riemannian manifold

This paper is concerned with the semilinear transmission of wave-plate system with source term on Riemannian manifold. We prove the existence of weak solutions by using Faedo-Galerkin's method. Furthermore, by introducing nonlinear boundary feedbacks acting only on plate, we establish the explicit and general decay rates of the system. Our proofs are based on the geometric multiplier method and the Riemannian geometry method.

Global weak solutions to the active hydrodynamics of liquid crystals

We consider the incompressible flow of the active hydrodynamics of liquid crystals with inhomogeneous density in the Beris-Edwards hydrodynamics framework. The Landau-de Gennes Q-tensor order parameter is used to describe the liquid crystalline ordering. Faedo-Galerkin's method is adopted to construct the solutions for the initial-boundary value problem. Two levels of approximations are used and the weak convergence is obtained through compactness estimates by new techniques due to the active terms. The existence of global weak solutions in dimension two and three is established in a bounded domain.

Analysis of a contact problem involving thermoelastic mixtures

In this work we study a dynamic contact problem between a thermoelastic mixture and a deformable obstacle. The classical normal compliance condition is used for modeling the contact. The variational formulation of this problem is written as a nonlinear coupled system of three parabolic variational equations. An existence and uniqueness result is proved using the Faedo-Galerkin method. Then, fully discrete approximations are introduced by using the finite element method and the implicit Euler scheme. A discrete stability property and a priori error estimates are proved, from which the decay of the discrete energy and the linear convergence of the algorithm are deduced. Finally, some numerical simulations are presented to show the convergence and the behavior of the solution.

Existence, blow-up and exponential decay estimates for a system of nonlinear viscoelastic wave equations with nonlinear boundary conditions

This paper is devoted to the study of a system of nonlinear viscoelastic wave equations with nonlinear boundary conditions. Based on the Faedo-Galerkin method and standard arguments of density corresponding to the regularity of initial conditions, we first establish two local existence theorems of weak solutions. By the construction of a suitable Lyapunov functional, we next prove a blow up result and a decay result of global solutions.

Numerical Solutions for Time-Fractional Cancer Invasion System With Nonlocal Diffusion

This article studies the existence and uniqueness of a weak solution of the time-fractional cancer invasion system with nonlocal diffusion operator. Existence and uniqueness results are ensured by adapting the Faedo-Galerkin method and some a priori estimates. Further, finite element numerical scheme is implemented for the considered system. Finally, various numerical computations are performed along with the convergence analysis of the scheme.

Asymptotic behavior of non-autonomous fractional stochastic [formula omitted]-Laplacian equations

This article is concerned with the asymptotic behavior of solutions of a wide class of non-autonomous, non-local, fractional, stochastic p-Laplacian equations driven by multiplicative white noise. The time-dependent nonlinear drift term of the equation has a polynomial growth of arbitrary order in its third component which is allowed to be greater than the exponent p. We first employ the Faedo–Galerkin method to prove the well-posedness of the equation in an appropriate Hilbert space. We then establish the existence, uniqueness and periodicity of tempered pullback random attractors for the equations. The upper semi-continuity of these attractors is also derived as the density of noise tends to zero. The results of this paper are new even when the stochastic equation reduces to the deterministic one.

Unfolding homogenization method applied to physiological and phenomenological bidomain models in electrocardiology

In this paper, we apply a rigorous homogenization method based on unfolding operators to a microscopic bidomain model representing the electrical activity of the heart at a cellular level. The heart is represented by an arbitrary open bounded connected domain with smooth boundary and the cardiac cells’ (myocytes) domain is viewed as a periodic region. We start by proving the well posedness of the microscopic problem by using Faedo–Galerkin method and L2-compactness argument on the membrane surface without any restrictive assumptions on the conductivity matrices. Using the unfolding method in homogenization, we show that the sequence of solutions constructed in the microscopic model converges to the solution of the macroscopic bidomain model. Because of the nonlinear ionic function, the proof is based on the surface unfolding method and Kolmogorov compactness argument.

Weak martingale solutions for the stochastic nonlinear Schrödinger equation driven by pure jump noise

We construct a martingale solution of the stochastic nonlinear Schrodinger equation (NLS) with a multiplicative noise of jump type in the Marcus canonical form. The problem is formulated in a general framework that covers the subcritical focusing and defocusing stochastic NLS in $$H^1$$ on compact manifolds and on bounded domains with various boundary conditions. The proof is based on a variant of the Faedo-Galerkin method. In the formulation of the approximated equations, finite dimensional operators derived from the Littlewood–Paley decomposition complement the classical orthogonal projections to guarantee uniform estimates. Further ingredients of the construction are tightness criteria in certain spaces of cadlag functions and Jakubowski’s generalization of the Skorohod-Theorem to nonmetric spaces.

Analysis of a Contact Problem Problem Involving an Elastic Body with Dual-Phase-Lag

In this work we study a contact problem between a thermoelastic body with dual-phase-lag and a deformable obstacle. The contact is modelled using a modification of the well-known normal compliance contact condition. An existence and uniqueness result is proved applying the Faedo–Galerkin method and Gronwall’s inequality. The exponential stability is also shown. Then, we introduce a fully discrete approximation by using the implicit Euler scheme and the finite element method. A discrete stability property and a priori error estimates are obtained, from which the linear convergence of the algorithm is derived under suitable regularity conditions. Finally, some numerical examples are presented to demonstrate the accuracy of the approximation and the behaviour of the solution.

Stochastically forced cardiac bidomain model

The bidomain system of degenerate reaction–diffusion equations is a well-established spatial model of electrical activity in cardiac tissue, with “reaction” linked to the cellular action potential and “diffusion” representing current flow between cells. The purpose of this paper is to introduce a “stochastically forced” version of the bidomain model that accounts for various random effects. We establish the existence of martingale (probabilistic weak) solutions to the stochastic bidomain model. The result is proved by means of an auxiliary nondegenerate system and the Faedo–Galerkin method. To prove convergence of the approximate solutions, we use the stochastic compactness method and Skorokhod–Jakubowski a.s. representations. Finally, via a pathwise uniqueness result, we conclude that the martingale solutions are pathwise (i.e., probabilistic strong) solutions.

СТОХАСТИЧЕСКАЯ МОДЕЛЬ ПРОЦЕССА РАЗДЕЛЕНИЯ СЛОЖНЫХ ГЕТЕРОГЕННЫХ ДИСПЕРСНЫХ СИСТЕМ В ЦЕНТРИФУГАХ С РАДИАЛЬНО-ОСЕВЫМ ПОТОКОМ

The article describes separation processes in apparatus with complex hydrodynamic conditions. The new approach to the theoretical study consists in taking into account the action of the centrifugal field and the field of random forces, as it was implemented earlier for the simplest structures, but also in a detailed examination of the radial and axial flows. The movement of particles is investigated in the cramped conditions of precipitation during their interaction with each other. The processes of separation in centrifugal devices of various types have been identified, subject to stochasticity, constrained movement of a set of real particles and the possibility of their dispersion and coagulation. The combined deterministic and stochastic effects on the dispersed phase in a centrifugal field are described by means of a differential equation, the solution of which makes it possible to calculate the fractional and total centrifugation efficiency with high accuracy. A semi-analytical method has been developed and implemented for one-and two-dimensional stochastic models for the approximate solution of non-stationary centrifugal boundary value problems. Compared to difference schemes Faedo-Galerkin method gives the solution of equation systems with a smaller number of unknowns defined in all values of the arguments. The use of the method is possible only in the case of homogeneous boundary conditions and is limited by the possibility of selecting a complete system of functions that would satisfy them. The proposed approach to identification of refining fuels and lubricants is preferable since it fully reflects the essence of the processes occurring in centrifuges with a radial-axial flow. Generalization of stochastic effects on centrifugation, taking into account the hydrodynamic features of the flow of shared media in a centrifugal field, allows calculating all indicators of cleaning fuels and oils from mechanical impurities without model experiments, predicting the total and fractional efficiency of fuel oil filters and oil filters of the internal combustion engines. The developed identification method of separating complex dispersed systems is aimed at the synthesis of systems and devices for oil purification and fuel oil preparation of increased efficiency with predetermined parameters of purification quality in operating conditions.

A shear flow problem for compressible viscous micropolar fluid: Derivation of the model and numerical solution

In this paper we consider the nonstationary shear flow between two parallel solid and thermoinsulated horizontal plates with the upper one moving irrotationally. The fluid is compressible, micropolar, viscous and heat-conducting, as well as in the thermodynamical sense perfect and polytropic. We assume that, given a Cartesian coordinate system x, y and z, solutions of corresponding problem are x-dependent only. Mathematical model is derived in the Lagrangian description. By using the Faedo–Galerkin method, as well as homogenization of boundary conditions, we derive an approximate system, which we use to obtain a numerical solution to the given problem.

General decay of the solution to a nonlinear viscoelastic modified von-Kármán system with delay

In this paper we consider a viscoelastic modified nonlinear Von-Kármán system with a linear delay term. The well posedness of solutions is proved using the Faedo-Galerkin method. We use minimal and general conditions on the relaxation function and establish a general decay results, from which the usual exponential and polynomial decay rates are only special cases.