A Two-Dimensional Model for the Combustion Chamber/Gun Tube of a Concept VIC Regenerative Liquid Propellant Gun

Standard interior ballistics models are generally lumped parameter models. This type of model has proven quite successful in modeling overall behavior in both solid and liquid propellant guns. However, some phenomena of interest cannot be reduced to lumped parameter form. One such phenomenon is high frequency pressure oscillations in liquid propellant guns. Pressure oscillations occur in almost all liquid propellant gun firings, and modeling requires at least a two-dimensional space. There is major uncertainty concerning the cause of these oscillations. In order to examine this problem, a two-dimensional fluid dynamics model of the combustion chamber and the gun tube of a liquid propellant gun has been developed. The code was run for a variety of test cases and gives reasonable results. Models were implemented with chamber dimensions and injection rates similar to actual Concept VIC guns. Oscillations were created that were very similar in magnitude to the experimental data, although the frequency structure was somewhat simpler. However, frequencies higher than the expected low-order acoustic modes were generated. A discussion is given concerning the causes of the oscillations in the model and the implications for reducing the oscillations in the actual guns.