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Limiting Theories in Material Science: Mathematical derivation and Analysis

Subject Area Mathematics
Term from 2016 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 313878761
 
Final Report Year 2024

Final Report Abstract

The project focused on three areas: pattern formation in wrinkled thin elastic sheets, regularity theory for solutions of elliptic and parabolic equations with degenerate coefficients and their implications, and singular limits in models for motion of compressible viscous fluids. Following previous work on wrinkling of circular sheet on spherical elastic substrate, whose wrinkling is caused by substrate induced curvature, we analyzed the model for the case of a general substrate (including a liquid drop model considered in experiments) and identified the energy scaling law for the leading order energy as well as next-order excess energy. In a different project, we extended the analysis of the optimal prefactor for the excess energy in a problem modeling transition from flat to wrinkled state via Γ-convergence. Starting point of the regularity results is sharp extension of classical work of Trudinger on local boundedness and validity of Harnack inequality for weak solutions of scalar elliptic equations with degenerate coefficients. We have also analyzed parabolic equations, and implications to quenched invariance principle for the random conductance model. Another area it applies to is regularity theory for critical points of double-phase variational integrals, as well as regularity for solutions of the p-Laplacian. In the third area we considered motion of compressible viscous fluids. In a series of papers we considered corresponding Navier-Stokes equations in smooth domains perforated by balls of radius εα and average distance ε. For these we studied the limiting behavior of global weak solutions as ε 0 and obtained different models describing the effective limiting problem depending on the parameter α. We also considered a full Navier-Stokes-Fourier model including temperature of the fluid, and studied two different limits while rescaling both the pressure and the forcing term. For one rescaling we obtained in the limit a well-established the Oberbeck-Boussinesq approximation but with a surprising nonlocal boundary conditions, related to the conservation of the total energy, while other rescaling gives in the limit “pancake model” proposed as a model for atmospheric flows by Majda.

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