Bloch-wave homogenization on large time scales and dispersive effective wave equations

We investigate second order linear wave equations in periodic media, aiming at the derivation of effective equations in ${\mathbb{R}}^n$, $n\in \{1,2,3\}$. Standard homogenization theory provides, for the limit of a small periodicity length $\text{eps}>0$, an effective second order wave equation that describes solutions on time intervals $[0,T]$. In order to approximate solutions on large time intervals $[0,T{\text{eps}}^{-2}]$, one has to use a dispersive, higher order wave equation. In this work, we provide a well-posed, weakly dispersive effective equation, and an estimate for errors between the solution of the original heterogeneous problem and the solution of the dispersive wave equation. We use Bloch-wave analysis to identify a family of relevant limit models and introduce an approach to select a well-posed effective model under symmetry assumptions on the periodic structure. The analytical results are confirmed and illustrated by numerical tests.