Numerical Investigation of Hydrogen Plumes and Comparison with Experiments in STG.

摘要

Hydrogen plumes gained much interest from the fact that H (sub 2) is an important reaction product of a hydrazine thruster. H (sub 2) shows strong and temperature dependant rotational relaxation which quickly leads to nonequilibrium between translational and rotational temperature in expanding flows. In a hybrid calculation of the whole flowfleld, both methods (Navier- Stokes and DSMC) must model rotational relaxation consistently. Jeans' equation was used for Navier-Stokes, and for DSMC the Borgnakke-Larsen model with constant and with energy-dependent relaxation probability was used. The comparison with free molecule probe measurements of hydrogen plumes in the DLR High Vacuum Facility STG provides insight into the accuracy of the numerical models.