Three-dimensional numerical modeling of a diagonal magnetohydrodynamic accelerator

The objective of this dissertation is to analyze the NASA Magnetohydrodynamic Augmented Propulsion Experiment (MAPX) using a three-dimensional numerical model---the results of which are intended to increase the understanding of the critical physical processes in the accelerator and provide pre-test cofiguration recommendations and performance predictions. Because of the three-dimensional (3-D) nature of magnetohydrodynamic (MHD) flows, a 3-D numerical model was required; however, no such numerical model existed for diagonal MHD accelerators.;Therefore, a parabolic 3-D numerical model, capable of simulating diagonal MHD accelerator flows, was developed from an existing MHD generator model. This new model can simulate partially ionized flows through the incorporation of the NASA Chemical Equilibrium with Applications code for calculation of thermodynamic and species concentration properties and a numerical technique based on electron-neutral momentum transfer cross-sections to calculate electrical conductivity.;This new 3-D MHD accelerator model was then used to analyze the MAPX accelerator. The recommended configuration for the MAPX accelerator is as follows: electrodes should have a 45 degree accelerator angle, the applied current should be 100 Ampheres, and the power takeoff should cover 5 electrodes at the entrance of the channel and two electrodes at the exit. Furthermore, the magnet pole flares located in the MAPX electromagnet should remain. Using this configuration, analysis shows an increase of 75% and a decrease of 25% in the cross-sectional averaged values of velocity and total pressure, respectively, from entrance to exit of the accelerator, with an electrical efficiency of approximately 45%. The low MAPX efficiency and total pressure losses result from the following sources of entropy. The MAPX channel has a high surface-to-volume ratio, which promotes secondary flows and strong localized axial currents. Viscous effects cause the drop in total pressure while axial currents result in large concentrations of electrons near the anode and excessive Joule heating.;This research marks the first in-depth, 3-D numerical analysis of an experimental diagonal MHD accelerator. The results of this research have helped to define the experimental configuration of the MAPX accelerator and offer a better understanding of the critical physical processes---including flow and temperature development, MHD flow interactions, electrical current behavior, total pressure effects, and entropy sources---that occur within a diagonal magnetohydrodynamic accelerator.