<p>In this paper we consider the time dependent Porous Medium Equation, <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(u_t = \Delta u^\gamma \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>u</mi> <mi>t</mi> </msub> <mo>=</mo> <mi mathvariant="normal">Δ</mi> <msup> <mi>u</mi> <mi>γ</mi> </msup> </mrow> </math></EquationSource> </InlineEquation> with real polytropic exponent <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\gamma &gt;1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>γ</mi> <mo>&gt;</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>, subject to a homogeneous Dirichlet boundary condition. We are interested in recovering <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\gamma \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation> from the knowledge of the solution <i>u</i> at a given large time <i>T</i>. Based on an asymptotic inequality satisfied by the solution <i>u</i>(<i>T</i>), we propose a numerical algorithm allowing us to recover <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\gamma \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation>. An upper bound for the error between the exact and recovered <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\gamma \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation> is then showed. Finally, numerical investigations are carried out in two and three dimensions.</p>

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Recovering the polytropic exponent in the porous medium equation: asymptotic approach

  • Hagop Karakazian,
  • Toni Sayah,
  • Faouzi Triki

摘要

In this paper we consider the time dependent Porous Medium Equation, \(u_t = \Delta u^\gamma \) u t = Δ u γ with real polytropic exponent \(\gamma >1\) γ > 1 , subject to a homogeneous Dirichlet boundary condition. We are interested in recovering \(\gamma \) γ from the knowledge of the solution u at a given large time T. Based on an asymptotic inequality satisfied by the solution u(T), we propose a numerical algorithm allowing us to recover \(\gamma \) γ . An upper bound for the error between the exact and recovered \(\gamma \) γ is then showed. Finally, numerical investigations are carried out in two and three dimensions.