Modeling of a small hydrazine thruster plume in the transition flow regime

Abstract

Three different techniques commonly employed in the calculation of rocket and thruster expansion plumes are assessed. These techniques vary both in computational expense and in the accuracy and detail of the solutions that they provide. The assessment is made with reference to the plume expanding from a small monopropellant hydrazine thruster and includes comparison with experimental data. Two of the modeling techniques, the Simons model and the Method of Characteristi cs, rely on the continuum equations. The third, the Direct Simulation Monte Carlo method (DSMC), adopts a discrete particle approach. The validity in employing continuum methods in the flowfield between the continuum and free molecular limits (i.e., the transition flow regime) is investigated. It is noted that the more computationally intensive DSMC solution method is the proper technique in this region of the expansion plume. Additional results provided solely by the DSMC calculations, such as thermal nonequilibrium effects, are presented. The consequences arising from the apparent differences in the results obtained with the continuum and discrete particle methods at the free molecular limit are assessed in terms of impingement effects.