A multiscale fast semi-Lagrangian method for rarefied gas dynamics

In this paper we consider the extension of the method developed in Dimarco and Loubère (2013) [22], [23] with the aim of facing the numerical resolution of multi-scale problems arising in rarefied gas dynamics. The scope of this work is to consider situations in which the whole domain does not demand the use of a kinetic model everywhere. This is the case of many realistic applications: some regions of the computational domain require a microscopic description, given by a kinetic model while the rest of the domain can be described by a coarser model of fluid type. Our aim is to show how the kinetic scheme developed in the pre-cited articles is perfectly suited for building domain decomposition strategies which make the method more attractive with respect to classical numerical techniques for kinetic equations and multi-scale realistic problems. Several numerical evidences are provided in this work in the two dimensional and three dimensional settings to assess the efficiency of the domain decomposition scheme.