On a Hele-Shaw Flow Problem with Free and Solid Boundary Components

The purpose of this work is to study a one phase Hele-Shaw fluid flow occupying a time variable domain \(\Omega (t)\), due to the injection of the fluid with a constant rate at a single point of the initial domain \(\Omega (0)\), and in the presence of a fixed solid body \(\Omega _0\). We show the short time existence and uniqueness of the solution for the corresponding boundary value problem in the three dimensional case and in the absence of surface tension.     

A Free Boundary Problem with Curvature

Abstract

In this paper we are interested in a free boundary problem with a motion law involving the mean curvature term of the free boundary. Viscosity solutions are introduced as a notion of global-time solutions past singularities. We show the comparison principle for viscosity solutions, which yields the existence of minimal and maximal solutions for given initial data. We also prove uniqueness of the solution for several classes of initial data and discuss the possibility of nonunique solutions.     

Analysis of a Free Boundary Problem Modeling Tumor Growth

In this paper, we study a free boundary problem arising from the modeling of tumor growth. The problem comprises two unknown functions： R = R（t）, the radius of the tumor, and u = u（r, t）, the concentration of nutrient in the tumor. The function u satisfies a nonlinear reaction diffusion equation in the region 0 〈 r 〈 R（t）, t 〉 0, and the function R satisfies a nonlinear integrodifferential equation containing u. Under some general conditions, we establish global existence of transient solutions, unique existence of a stationary solution, and convergence of transient solutions toward the stationary solution as t →∞.     

Boundary Estimates for Solutions of the Parabolic Free Boundary Problem

Let u and solve the problem

On a Moving Boundary Problem from Biomechanics

A moving boundary problem arising in biomechanical diffusiontheory which has previously been investigated by Crank &Gupta (1972a, b) is studied using a different method of solution.The method is based on an integral equation for the functiondefining the position of the moving boundary and an integralformula for the concentration. The integral equation is solvedasymptotically for small times and numerically during the entiremotion of the boundary. The concentration is estimated asymptoticallyfor small times and computed by numerical quadrature at laterinstants. The results are compared with those of Crank &Gupta. In most cases the agreement is fair.     

A Free Boundary Problem Arising in Smoulder Combustion

The smouldering combustion is modeled as a free boundary problem here. By using the Duvaut's transform, the problem is reduced to a variational inequality. Existence and uniqueness are established. Tbe properties of the free boundary are studied in various cases. The asymptotic behavior of the free boundary with respect to the parameter is rigorously proved, which confirms the result of a previous work by J. Adler and D. M. Herbert, obtained by using asymptotic expansion. Furthermore, we show that the time dependent problem will actually converge to a travelling wave solution if the boundary data converge to the corresponding travelling wave solution.     

Local Classical Solution of Muskat Free Boundary Problem

In this paper we consider the two-dimensional Muskat free boundary problem: Δu_i(x,t) = 0 in space-time domain Q_i (i = 1,2), here tis a parameter. The unknown surface Γ_pT (free boundary) is tltc common part of the boundaries of Q_1 and Q_2. The free boundary conditions are u_1(x,t) = u_2(x,t) and -k_1\frac{∂u_1}{∂n} = -k_2\frac{∂u_2}{∂n} = V_n. If the initial normal velocity of the free boundary is positive, we shall prove the existence of classical solution locally in time and uniqueness by making use of Newton's iteration method.     

Inverse Problem with Free Boundary for Heat Equation

We establish conditions for the existence and uniqueness of a solution of the inverse problem for a one-dimensional heat equation with unknown time-dependent leading coefficient in the case where a part of the boundary of the domain is unknown.     

Global Existence for a Parabolic-hyperbolic Free Boundary Problem Modelling Tumor Growth

In this paper we study a free boundary problem modelling tumor growth, proposed by A. Friedman in 2004. This free boundary problem involves a nonlinear second-order parabolic equation describing the diffusion of nutrient in the tumor, and three nonlinear first-order hyperbolic equations describing the evolution of proliferative cells, quiescent cells and dead cells, respectively. By applying Lp theory of parabolic equations, the characteristic theory of hyperbolic equations, and the Banach fixed point theorem, we prove that this problem has a unique global classical solution.     

Numerical Solution of a Parabolic Free Boundary Problem via Newton's Method

We develop a Newton-like numerical method to solve a free boundaryproblem of parabolic type. From some numerical tests we concludethat the speed of convergence of this procedure is very high,probably quadratic in the neighbourhood of the solution.     

一类周期自由边界问题解的渐近性态

本文证明了化学反应扩散过程中的一类周期自由边界问题古典解的存在唯一性，并且讨论了潜热L→0时周期Stefan问题古典解的渐近性态及误差估计．     

The Hopf Bifurcation in a Parabolic Free Boundary Problem with Double Layers

We consider a parabolic free boundary problem which has a bifurcation parameter and double interfaces. We investigate the sign change in a real part of eigenvalues and the transversality condition as a bifurcation parameter cross the critical value in order to examine the stability of the stationary solutions. The occurence of a Hopf bifurcation will be shown at a critical value.     

具有自由边界的二维渗流问题

渗流的自由边界问题是工程上很受关注的问题．现有的数值分析方法需事先估计边界形态，逐次逼近．本文采用“变分不等式”的模式，结合有限元方法研究有自由边界的渗流问题，在整个结构区域内作有限元剖分，避免了传统的有限元分析中估计自由边界、反复修正计算区域的迭代过程．本文方法为简单而快速地分析渗流自由边界问题提供了一条有效的途径．     

A Free Boundary Problem Modelling the Electrolysis of Aluminium

The goal of this note is to show existence and uniqueness for a stationary one-phase Stefan problem with source at the free boundary modelling the electrolysis of aluminium.