## On the uniqueness of the solution of the evolution dam problem

### Impacto

Carrillo Menéndez, José (1994) On the uniqueness of the solution of the evolution dam problem. Nonlinear Analysis: Theory, Methods & Applications, 22 (5). pp. 573-607. ISSN 0362-546X

## Abstract

The purpose here is to investigate some aspects of the evolution dam problem $\partial(\chi+\alpha u)/\partial t=\Delta u+{\rm div}(\chi e)$ in $Q$, $\chi\in H(u)$ in $Q$, $u\geq 0$ in $Q$, $u=\phi$ in $\Sigma_2$, $\partial u/\partial v+\chi ev\leq 0$ on $\Sigma_2\cap \{\phi=0\}$, $e\in {\bf R}^n$, $e=(0,\cdots, 0,1)$, $\partial u/\partial v+\chi ev=0$ on $\Sigma_1$. Here $H$ is the Heaviside maximal graph $H(s)=1$ if $s>0$, $H(s)=[0,1]$ if $s=0$, $\alpha$ is the storativity constant: $\alpha=0$ if the fluid is incompressible and $\alpha>0$ if the fluid is compressible. Also $Q=\Omega\times (0,T)$ where $\Omega$ is a bounded domain in ${\bf R}^n$ ($\Omega$ represents a porous medium separating a finite number of reservoirs) with Lipschitz boundary $G$ where $G$ is divided into two parts: $G_1$, which is the impervious part, and $G_2$, which is the pervious part, with the following assumptions: $G_2$ is an open subset of $G$, $G_2\not=\emptyset$, $G_2\cap G_1=\emptyset$, $G_2\cup G_1=G$ and $e\nu\leq 0$ a.e. on $G_1$; $\Sigma_i$ denotes $G_i\times (0,T)$, $i=1,2$. The pressure at $\Sigma_2$ is known and is represented by a nonnegative function $\phi\in C^{0,1}(\overline Q)$. The above problem can be completed by prescribing an initial value to $\chi+\alpha u$. The existence of a weak solution of the evolution dam problem is well known; however, many properties of the solutions of the initial value dam problem, in particular, comparison and uniqueness theorems, continue to be open for a general domain $\Omega$. The results of this paper give precise information about the comparison (Theorem 4.7) and the uniqueness (Corollary 4.9) statements. The key point to prove comparison and uniqueness results is that the function $h\mapsto \chi(x',x_n+h, t-h)$, $x'\in{\bf R}^{n-1}$, is a.e. nonincreasing

Item Type: Article Free boundary problems; Flows in porous media; filtration Sciences > Mathematics > Differential equations 15598 12 Jun 2012 09:57 18 Apr 2013 14:03

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