Supersaturation Total Temperature, Pitot Pressure, and Rayleigh Scattering Measurements at Mach 10
A fundamental research study of the supersaturation region is presented. This region is mapped in the NASA Langley 31-Inch Mach 10 Air Wind Tunnel freestream flow using physical probes (total temperature and pitot) and a nonintrusive offbody diagnostic (laser Rayleigh scattering). Data from all three methods are acquired simultaneously. Facility stagnation pressures spanned 1.0–10.0 MPa (150–1450 psi), and stagnation temperatures spanned 357–1000 K (184–1350°F). Each instrument has its own unique supersaturation region over which quantitative measurements can be obtained. The extent of each supersaturation region is a unique function of the sensitivity of the instrument selected to flowfield clustering. Laser-Rayleigh-scattering-measured density results agree to better than 15% with the freestream density computed using the GASPROPS code over a significant fraction of the supersaturation region. Evidence is presented showing that the “frozen” vibrational nonequilibrium Boltzmann population of O2 and N2 mo...