Ultra-high-speed camera with laser-induced fluorescence characterizes hypersonic nitric oxide
Ultra-high-speed camera with laser-induced fluorescence characterizes hypersonic nitric oxide lead image
As interest in hypersonic flight continues to build, increasing work has focused on the environment in the immediate vicinity of hypersonic objects. Nitric oxide formed by shock waves provides a useful tool for assessing flow structures and heat distributions.
Leonov et al. conducted a set of experiments to better characterize the morphology of nitric oxide under such conditions. By using camera coupled planar laser-induced fluorescence (PLIF) techniques to take measurements up to half a million times per second, they compared findings from wedges in the hypersonic flows with industry-standard simulations.
“We had quite a unique diagnostic setup that allowed us to overcome some of the challenges of working with extremely hot hypersonic environments,” said author Boris Leonov. “Additionally, we have applied the diagnostic setup and data collected to a relatively new approach of computational fluid dynamics validation.”
At hypersonic speeds – Mach 5 or faster – air compressed by strong shock waves can reach temperatures over 5000 degrees Fahrenheit.
Quantitative comparisons showed that the CFD agreed well with experimental findings regarding the target species concentration across a wide range of temperatures, with less than 1.5% of a difference between the PLIF and simulated signals in the thermally equilibrated regions.
Such findings held true even for thermal non-equilibrium portions of the flow, where the stagnation enthalpy, a measure of the energy of a flowing fluid stream, was set at 7 megajoules per kilogram. Discrepancies, however, arose when the intensity was pushed to 10 megajoules per kilogram.
The group next looks to extend their work to faster speeds and hotter flows as well as investigate other thermochemical products of hypersonic flight.
Source: “High-speed planar laser-induced fluorescence investigation of nitric oxide generated by hypersonic Mach reflections for computational fluid dynamics validation,” by Boris S Leonov, Tyler S Dean, Christopher Limbach, Rodney Bowersox, and Richard B. Miles, Physics of Fluids (2023). The article can be accessed at https://doi.org/10.1063/5.0150273 .
