Simulation of time resolved radiative emission in the X2 expansion tube

Abstract

During Earth entry X2 expansion tube experiments, it was discovered that post-shock atomic oxygen and nitrogen radiative emission were dropping during the test time, even though pressure is seen to rise. This sparked an interest to investigate further, to see if a onedimensional computational fluid dynamic model could qualitatively replicate the X2 experimental results and further analyse what occurs across multiple wavelength regions in the test time. From the qualitative study it was observed that most of the free-stream and post-shock flow properties besides Mach number aren’t constant in the test time for the model condition. Given pitot pressure and post-shock temperature are dominant properties in dictating radiative emission, it is reasonable to observe why multiple wavelength regions had non-constant radiative emission also. From the results it was observed that the atomic oxygen and nitrogen radiative emission was falling in the test time, supporting X2 experimental findings. This suggests going forward that radiative emission studies at UQ Hypersonics for this particular Earth entry condition shouldn’t assume the atomic oxygen and nitrogen wavelength region to be constant. In addition, the radiative emission from one wavelength region should be considered to act independently from other wavelength regions.