The effect of expansion on the large scale structure of a compressible turbulent boundary layer

Stephen A. Arnette, Mo Samimy, Gregory S. Elliott

Research output: Contribution to conferencePaperpeer-review


This paper presents the initial results of an extended investigation of the effects of expansion on high Reynolds number, compressible, turbulent boundary layers. Extensive flow visualizations have been performed, mainly with filtered Rayleigh scattering, for the purpose of investigating the large scale features of the boundary layer turbulence. The incoming flow is a Mach 3 fully-developed boundary layer. For this incoming flow, five cases are visualized: the unperturbed flat plate boundary layer and the boundary layer after 7° and 14° centered expansions and 7° and 14° gradual expansions. In addition to the previously known large scale structures of the outer layer, visualizations of the unperturbed boundary layer reveal the presence of well-defined turbulent structures of a very large streamwise, and limited spanwise, extent. As such, these ‘streaky’ structures appear similar to those found near the wall of incompressible boundary layers. However, these structures were found well above the inner layer, nominally at y/δ = 0.5-1.0. Although they may be present even closer to the wall, this region cannot be probed with the employed visualization technique. The fact that the streaks were seen to populate most of the thickness of the boundary layer suggests the streaks are a fairly robust feature of the compressible boundary layer. The streamwise structures were also found to exist in the expanded boundary layers. The appearance of the streaks in the two 7° expansion cases showed no noticeable differences from the flat plate case, while it appeared that the streaks might be less prevalent and of a shorter streamwise extent in the 14°cases relative to the flat plate.

Original languageEnglish (US)
StatePublished - 1993
Externally publishedYes
EventAIAA 23rd Fluid Dynamics, Plasmadynamics, and Lasers Conference, 1993 - Orlando, United States
Duration: Jul 6 1993Jul 9 1993


OtherAIAA 23rd Fluid Dynamics, Plasmadynamics, and Lasers Conference, 1993
Country/TerritoryUnited States

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electrical and Electronic Engineering
  • Aerospace Engineering
  • Engineering (miscellaneous)


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