Coarse graining strategies at walls

Abstract

We review four fundamental approaches to include system boundaries into the coarse graining formalism, particularly with regard to simulations of granular media, and formulate criteria for evaluating their usability. A simple lattice system illustrates their application and respective advantages. We show that only one of them is able to fully reproduce the conservation laws of mechanics without further restrictions. Nevertheless, some of the other schemes are found to be better suited when dynamics is not the subject of interest.