Direct simulation of high-altitude ultraviolet emission from the hydroxyl radical

Koffi K. Kossi, Iain D. Boyd, Deborah A. Levin

Research output: Contribution to journalArticlepeer-review


Ultraviolet emissions radiated by hydroxyl (OH) are computed for hypersonic nonequilibrium flow conditions corresponding to the Bow-Shock Ultra-Violet-2 flight experiment. The flowfield is analyzed using the direct simulation Monte Carlo method. These computations include direct analysis of the electronically excited state of hydroxyl. Ultraviolet emission is estimated using a nonequilibrium radiation code. New algorithms are described that improve the numerical resolution of the excited state that occurs at number densities as low as 10-3 cm-3. Results are presented for the altitude range from 80 to 100 km. It is shown that the high-altitude emission is sensitive to modeling of the interaction of the gas with the vehicle surface. Sensitivity of emission predictions to freestream concentrations of hydrogen-bearing species is also considered. It is found that the quasi-steady-state assumption often employed in the nonequilibrium radiation code is invalid at high altitude. Comparison of the predicted values for peak OH emission with flight measurements indicates good agreement. Detailed comparisons of the spectra, however, indicate that the simulations fail to include strong nonequilibrium effects observed in the measured data.

Original languageEnglish (US)
Pages (from-to)223-229
Number of pages7
JournalJournal of thermophysics and heat transfer
Issue number2
StatePublished - 1998
Externally publishedYes

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Aerospace Engineering
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes
  • Space and Planetary Science


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