Asymptotic analysis of a contact Hele-Shaw problem in a thin domain

Abstract: We analyze the contact Hele-Shaw problem with zero surface tension of a free boundary in a thin domain $\Omega^{\varepsilon}(t).$ Under suitable conditions on the given data, the one-valued local classical solvability of the problem for each fixed value of the parameter $\varepsilon$ is proved. Using the multiscale analysis, we study the asymptotic behavior of this problem as $\varepsilon \to 0,$ i.e., when the thin domain $\Omega^{\varepsilon}(t)$ is shrunk into the interval $(0, l).$ Namely, we find exact representation of the free boundary for $t\in[0,T],$ derive the corresponding limit problem $(\varepsilon= 0),$ define other terms of the asymptotic approximation and prove appropriate asymptotic estimates that justify this approach. We also establish the preserving geometry of the free boundary near corner points for $t\in[0,T]$ under assumption that free and fixed boundaries form right angles at the initial time $t=0$.