Modelling of N2-Thruster plumes based on experiments in STG

In the DLR- high vacuum plume test facility STG experiments have been performed with the aim to validate the available plume flow model. For this purpose fully expanding simulated plumes with N2 as test gas have been chosen as simplest case (no chemical reactions, constant ratio of specific heats). The essential parameter to be varied was the nozzle flow Reynolds number, the quantities to be measured were the Pitot pressure at the nozzle exit and the molecule number flux in the plume. It turned out that a new model had to be written taking into account in a more appropriate way the development of the boundary layer in the nozzle and the initial plume spreading. The result is a code which describes the plume flow in satisfying agreement with the experimental data.