Comparison of Decoupled Hybrid Navier-Stokes - DSMC Calculations with Experiments in Plumes

Abstract

Hybrid computation methods coupling Navier-Stokes solvers for continuum and DSMC methods for rarefied flow have gained much interest to treat flow conditions where strong nonequilibrium and large expansion ratios occur in hypersonic flow, e.g. in shocks, blunt body wakes and around nozzle lips [1, 2]. The present paper concerns, as a first step from the effort to build and validate such a program, decoupled Navier-Stokes-DSMC calculations of a nozzle flow. This case gains interest from the opportunity of comparing it to corresponding experiments from the new DLR High Vacuum Facility STG. By powerful cryopumps, STG allows reliable measurements in nozzle flow regions formerly not accessible due to background pressure disturbances, such delivering data urgently needed to check computational models over the whole range of flow conditions. Especially hybrid methods with their sensitive parameters controlling switching and DSMC details rely on such possibility for validation.