Comparison of Focker-Planck and CFD simulations of the RFZ-ST2 upper stage

Abstract

We simulate the generic upper stage RFZ-ST2 model with both computational fluid dynamics (CFD) and Focker-Planck (FP) methods. We use the well established DLR Tau code for the CFD simulations and an in-house FP extension to the DSMC code SPARTA. The simulations are done close to the continuum limit and are done using models for dissociation and vibrational excitation. The goals are both to validate the models of the FP implementation versus the well established CFD code and to investigate the limitation of the CFD towards higher Knudsen numbers. Therefore, we compare the resulting flow fields and surface distributions for different boundary conditions and for different modelling complexity. We also use this work to introduce the RFZ-ST2 model, an open source model of a generic upper stage, to the high speed aerothermodynamics community.