Analytical solution of a double moving boundary problem for nonlinear flows in one-dimensional semi-infinite long porous media with low permeability简

Based on Huang＇s accurate tri-sectional nonlin- ear kinematic equation （1997）, a dimensionless simplified mathematical model for nonlinear flow in one-dimensional semi-infinite long porous media with low permeability is presented for the case of a constant flow rate on the inner boundary. This model contains double moving boundaries, including an internal moving boundary and an external mov- ing boundary, which are different from the classical Stefan problem in heat conduction： The velocity of the external moving boundary is proportional to the second derivative of the unknown pressure function with respect to the distance parameter on this boundary. Through a similarity transfor- mation, the nonlinear partial differential equation （PDE） sys- tem is transformed into a linear PDE system. Then an ana- lytical solution is obtained for the dimensionless simplified mathematical model. This solution can be used for strictly checking the validity of numerical methods in solving such nonlinear mathematical models for flows in low-permeable porous media for petroleum engineering applications. Finally, through plotted comparison curves from the exact an- alytical solution, the sensitive effects of three characteristic parameters are discussed. It is concluded that with a decrease in the dimensionless critical pressure gradient, the sensi- tive effects of the dimensionless variable on the dimension- less pressure distribution and dimensionless pressure gradi- ent distribution become more serious; with an increase in the dimensionless pseudo threshold pressure gradient, the sensi- tive effects of the dimensionless variable become more serious; the dimensionless threshold pressure gradient （TPG） has a great effect on the external moving boundary but has little effect on the internal moving boundary.     

A moving finite element method for the population balance equation

A moving finite element algorithm has been compared against the upwind-differencing and Smolarkiewicz methods for the population balance equation of multicomponent particle growth processes. Analytical solutions and an error function have been used to test the numerical methods. The moving finite elements technique is much more accurate than other methods for a wide range of parameters. Since this method uses moving grids, it is able to model very narrow particle size distributions. It is also shown that the method can be extended to solve condensational growth problems which include particle curvature and non-continuum mass transfer effects.     

ON THE GENERAL SOLUTION OF CYLINDRICAL SHELL EQUATIONS

ＯＮ　ＴＨＥ　ＧＥＮＥＲＡＬ　ＳＯＬＵＴＩＯＮ　ＯＦ　ＣＹＬＩＮＤＲＩＣＡＬ　ＳＨＥＬＬ　ＥＱＵＡＴＩＯＮＳＰｅｔｅｒＹｉＸｕｅ（薛毅）；ＸｕｅＤａｗｅｉ（薛大为）（ＲｅｃｅｉｖｅｄＯｃｔ．１６，１９９５）Ａｂｓｔｒａｃｔ：Ｉｔｉｓｐｒｏｖｅｄｍａｔ...     

The existence of solution of a class of two-order quasilinear boundary value problem

Ref. [1] discussed the existence of positive solutions of quasilinear two-point boundary problems: but it restricts O相似文献   

Numerical solution of a singularly perturbed elliptichyperbolic partial differential equation on a nonuniform discretization mesh

In this paper, we consider the upwind difference scheme for singular perturbation problem (1.1). On a special discretization mesh, it is proved that the solution of the upwind difference scheme is first order convergent, uniformly in the small parameter ε, to the solution of problem (1.1). Numerical results are finally provided.     

THE NUMERICAL SOLUTION OF A SINGULARLY PERTURBED PROBLEM FOR SEMILINEAR PARABOLIC DIFFERENTIAL EQUATION

The numerical solution of a singularly perturbed problem for the semilinear parabolicdifferential equation with parabolic boundary layers is discussed.A nonlinear two-leveldifference scheme is constructed on the special non-uniform grids.The uniform convergenceof this scheme is proved and some numerical examples are given.     

A singular perturbation problem for periodic boundary partial differential equation

In this paper,we consider a singular perturbation elliptic-parabolic partial differentialequation for periodic boundary value problem,and construct a difference scheme.Using themethod of decomposing the singular term from its solution and combining an asymptoticexpansion of the equation,we prove that the scheme constructed by this paper convergesuniformly to the solution of its original problem with O(τ h~2).     

Numerical solution of nonlinear ordinary differential equation for a turning point problem

By using the method in[3],several useful estimations of the derivatives of the solutionof the boundary value problem for a nonlinear ordinary differential equation with a turningpoint are obtained.With the help of the technique in[4],the uniform convergence on thesmall parameterεfor a difference scheme is proved.At the end of this paper,a numericalexample is given.The numerical result coincides with theoretical analysis.     

极坐标平面问题的四阶差分及应用

推导出了极坐标系下双调和方程的差分公式，用逐次超松弛迭代法求出圆板平面应力问题的差分解，并和解析解作比较，验证了差分公式的正确性，为解决圆域及其类似区域的平面问题提供了新方法．     

GLOBAL SOLUTION OF THE INVERSE PROBLEM FOR ACLASS OF NONLINEAR EVOLUTION EQUATIONSOF DISPERSIVE TYPE

ＩｎｔｒｏｄｕｃｔｉｏｎＩｔｉｓｗｅｌｌ＿ｋｎｏｗｎｔｈａｔｐｓｅｕｄｏ＿ｐａｒａｂｏｌｉｃｅｑｕａｔｉｏｎｗｉｔｈｐｒｉｎｃｉｐａｌｐａｒｔｕｔ -ｕｘｘｔｈａｓｂｅｅｎｓｔｕｄｙｉｎｇｒｅｃｅｎｔｌｙ ,ｂｅｃａｕｓｅｔｈｅｒｅｅｘｉｓｔｓｗｉｄｅｐｈｙｓｉｃａｌｂａｃｋｇｒｏｕｎｄｆｏｒｔｈｉｓｃｌａｓｓｏｆｅｑｕａｔｉｏｎｓ.[1 ]ｓｔｕｄｉｅｄｔｈｅｍｕｌｔｉ＿ｄｉｍｅｎｓｉｏｎｉｎｖｅｒｓｅｐｒｏｂｌｅｍｆｏｒｔｈｅｆｏｌｌｏｗｉｎｇｃｌａｓｓｏｆｎｏｎｌｉｎｅａｒｅｖｏｌｕｔｉｏｎｅｑｕ…     

Global solution of the inverse problem for a class of nonlinear evolution equations of dispersive type

The inverse problem for a class of nonlinear evolution equations of dispersive type was reduced to Cauchy problem of nonlinear evolution equation in an abstract space. By means of the semigroup method and equipping equivalent norm technique, the existence and uniqueness theorem of global solution was obtained for this class of abstract evolution equations, and was applied to the inverse problem discussed here. The existence and uniqueness theorem of global solution was given for this class of nonlinear evolution equations of dispersive type. The results extend and generalize essentially the related results of the existence and uniqueness of local solution presented by YUAN Zhong-xin. Contributed by Chen Yu-shu Foundation item: the National Natural Science Foundation of China (Significance 199990510); the National Key Basic Research Special Foundation of China (G1998020316); Liuhui Center for Applied Mathematics, Nankai University & Tianjin University Biography: Chen Fang-qi (1963-)     

On the problem of preventing blowing-up and quenching for semilinear heat equation

In this paper,the global existence of solutions to the IVP=Δu+g(t)f(u) (t>0),u|_(t=0)=u_0(x)and the (?)PVPu_t=Δu-g(t,x)f(u)(t>0,x∈Ω),u|_(t-0)=u|_(?)(?)is investigated. As has been done in [6]the (?)duction of factor g(t) or g(t.x) innonlinear term is to prevent(?) occurrance of blowing-up or quenching of solutions.It isshown in this paper that most of the restrictions on f,g and u_0 in the theorems of[6] maybe cancelled or relaxed,that the smallness of g is required only for t large,and thatunder certain conditions controlling initial state can avoid blowing-up.     

Transversal vibrations of the axially moving sandwich belts

Inspired by literature on free transversal vibrations of one axially moving belt, we derive and solve analytically coupled partial differential equations of the transversal vibrations of an axially moving sandwich double-belt system. A numerical experiment and visualization are carried out.     

Numerical perturbation method for approximate solution of poisson's equation on a moderately deforming grid

In problems such as the computation of incompressible flows with moving boundaries, it may be necessary to solve Poisson's equation on a large sequence of related grids. In this paper the LU decomposition of the matrix A ₀ representing Poisson's equation discretized on one grid is used to efficiently obtain an approximate solution on a perturbation of that grid. Instead of doing an LU decomposition of the new matrix A , the RHS is perturbed by a Taylor expansion of A ^?1 about A ₀. Each term in the resulting series requires one ‘backsolve’ using the original LU . Tests using Laplace's equation on a square/rectangle deformation look promising; three and seven correction terms for deformations of 20% and 40% respectively yielded better than 1% accuracy. As another test, Poisson's equation was solved in an ellipse (fully developed flow in a duct) of aspect ratio 2/3 by perturbing about a circle; one correction term yielded better than 1% accuracy. Envisioned applications other than the computation of unsteady incompressible flow include: three-dimensional parabolic problems in tubes of varying cross-section, use of ‘elimination’ techniques other than LU decomposition, and the solution of PDEs other than Poisson's equation.     

A general solution of the axisymmetric contact problem for biphasic cartilage layers

A unilateral axisymmetric contact problem for articular cartilage layers is considered. The articular cartilages bonded to subchondral bones are modeled as biphasic materials consisting of a solid phase and a fluid phase. It is assumed that the subchondral bones are rigid and shaped like bodies of revolution with arbitrary convex profiles. The obtained closed-form analytical solution is valid over time periods compared with the typical diffusion time and can be used for increasing loading.     

一类基于Hamilton体系的半解析法

利用偏微分方程在Hamilton体系中的表示和二类变量变分原理,结合有限元法,提出一类基于Hamilton体系的半解析法。本文以二阶非齐次椭圆型方程为例,给出了这类半解析法中的一种的有限元列式和算例,与解析解、Ritz法、有限条法和有限元法的结果比较表明,此法具有较高的精度,还可求解其它其些偏微分方程,有一定的普遍意义。     

A general solution of axisymmetric problem of arbitrary thick spherical shell and solid sphere

In this paper, the axisymmetric problems of arbitrary thick spherical shell and solid sphere are studied directly from equilibrium equations of three-dimensional problem, and the general solutions in forms of Legendre series for thick spherical shell and solid sphere are given by using the method of weighted residuals.     

A least square extrapolation method for the a posteriori error estimate of the incompressible Navier Stokes problem

A posteriori error estimators are fundamental tools for providing confidence in the numerical computation of PDEs. To date, the main theories of a posteriori estimators have been developed largely in the finite element framework, for either linear elliptic operators or non‐linear PDEs in the absence of disparate length scales. On the other hand, there is a strong interest in using grid refinement combined with Richardson extrapolation to produce CFD solutions with improved accuracy and, therefore, a posteriori error estimates. But in practice, the effective order of a numerical method often depends on space location and is not uniform, rendering the Richardson extrapolation method unreliable. We have recently introduced (Garbey, 13th International Conference on Domain Decomposition, Barcelona, 2002; 379–386; Garbey and Shyy, J. Comput. Phys. 2003; 186 :1–23) a new method which estimates the order of convergence of a computation as the solution of a least square minimization problem on the residual. This method, called least square extrapolation, introduces a framework facilitating multi‐level extrapolation, improves accuracy and provides a posteriori error estimate. This method can accommodate different grid arrangements. The goal of this paper is to investigate the power and limits of this method via incompressible Navier Stokes flow computations. Copyright © 2005 John Wiley & Sons, Ltd.     

On periodic indentation of a rigid solid occupying a wavy surface moving on multiferroic materials

The present article is concerned with a 2D dynamic contact problem of a rigid solid occupying a wavy surface moving on anisotropic multiferroic materials. Three bulk wave velocities for anisotropic multiferroic materials are obtained. Five harmonic functions are suggested to derive the general solutions of anisotropic multiferroic governing equations based on the generalized Almansi’s theorem. The contact length and various stresses, electric displacements, and magnetic inductions can be given in the whole half-plane analytically. Figures are plotted to gain an insight of how the velocity and the elastic coefficient influence the contact performance of anisotropic multiferroic materials. Numerical results show that the contact length can be enlarged by escalating the velocity of the rigid solid.     

A SYMBOLIC COMPUTATION METHOD TO DECIDE THE COMPLETENESS OF THE SOLUTIONS TO THE SYSTEM OF LINEAR PARTIAL DIFFERENTIAL EQUATIONS

ＩｎｔｒｏｄｕｃｔｉｏｎＣｏｎｓｉｄｅｒｔｈｅｓｙｓｔｅｍｏｆｐａｒｔｉａｌｄｉｆｆｅｒｅｎｔｉａｌａｌｇｅｂｒａｉｃｅｑｕａｔｉｏｎｓ (ＰＤＡＥｓ) :Σ :　Ｐｉ(ｙ1,ｙ2 ,… ,ｙｎ) =0　　 (ｉ =1,2 ,… ,ｒ) ,ｗｈｅｒｅｔｈｅｃｏｅｆｆｉｃｉｅｎｔｓａｒｅｉｎｔｈｅｄｉｆｆｅｒｅｎｔｉａｌｆｉｅｌｄＫｗｉｔｈｃｈａｒａｃｔｅｒｉｓｔｉｃｚｅｒｏ .ＴｈｅｉｍｐｏｒｔａｎｔｑｕｅｓｔｉｏｎｉｓｈｏｗｔｏｓｏｌｖｅｔｈｉｓＰＤＡＥｓｉｎｔｈｅｔｈｅｏｒｙｏｆｐａｒｔｉａｌｄｉｆｆｅｒｅｎｔｉａｌｅｑｕａ…