A hybrid continuum-particle solver for unsteady rarefied gas flows

The implementation of a hybrid simulation algorithm based on the compressible Navier–Stokes equations and the Direct Simulation Monte Carlo (DSMC) method is discussed, with emphasis on problems of transient nature. The coupling of the two methods at their common interface is achieved by the generation of particles according to the local Maxwellian distribution and the imposition of macroscopic quantities for the continuum solver. Dynamic characteristics of the continuum-particle decomposition scheme lead to a flexible and fully configurable determination of the two regions. The parallelization scheme and the ability to consider arbitrary geometries allow the consideration of the method for non-trivial, practical applications. The validation of the code is performed for two benchmark problems, namely those of shock tube flow and unsteady flow through an orifice.