Multi-scale modelling of the two-dimensional flow dynamics in a stationary supersonic hot gas expansion

Abstract

A stationary hot gas jet supersonically expanding into a low pressure environment is studied through multi-scale numerical simulations. A hybrid continuum-molecular approach is used to model the flow. Due to the low pressure and high thermodynamic gradients, the accuracy of continuum mechanics results are doubtful, while, because of its excessive time expenses, a full molecular method is not feasible. The results of the proposed hybrid continuum-molecular approach have been successfully validated against experimental data. An important question for the full understanding of the processes governing the flow is addressed: the demonstration of an invasion of the supersonic part of the flow by background particles. Through the tracking of particles and collisions in the supersonic region it could be definitively proven that background particles are present in this region. We present a complete two dimensional picture of how the invading background particles distribute and collide with local particles into the supersonic region. © 2008 Springer-Verlag Berlin Heidelberg.