Visualizing supersonic inlet duct unstart using planar laser Rayleigh scattering

Hyungrok Do, Seong Kyun Im, M. Godfrey Mungal, Mark A. Cappelli

Research output: Contribution to journalArticlepeer-review

68 Citations (Scopus)


Planar laser Rayleigh scattering (PLRS) from condensed CO2 particles is used to visualize flow structure in a Mach 5 wind tunnel undergoing unstart. Detailed flow features such as laminar/turbulent boundary layers and shockwaves are readily illustrated by the technique. A downstream transverse air jet, inducing flow unchoking downstream of the jet, is injected into the free stream flow of the tunnel, resulting in tunnel unstart. Time sequential PLRS images reveal that the boundary layer growth/separation on a surface with a thick turbulent boundary layer, initiated by the jet injection, propagates upstream and produces an oblique unstart shock. The tunnel unstarts upon the arrival of the shock at the inlet. In contrast, earlier flow separation on the opposite surface, initially supporting a thin laminar boundary layer, is observed when a jet induced bow shock strikes that surface. The resulting disturbance to this boundary layer also propagates upstream and precedes the formation of an unstart shock.

Original languageEnglish
Pages (from-to)1651-1657
Number of pages7
JournalExperiments in Fluids
Issue number6
Publication statusPublished - 2011 Jun
Externally publishedYes

ASJC Scopus subject areas

  • Computational Mechanics
  • Mechanics of Materials
  • Physics and Astronomy(all)
  • Fluid Flow and Transfer Processes


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