Shock unsteadiness in a reattaching shear layer

J. Poggie, A. J. Smits

Research output: Contribution to conferencePaperpeer-review


The origin of shock unsteadiness in a Mach 2.9 turbulent, reattaching shear layer was investigated experimentally using temporally-resolved flow visualization and measurements of wall pressure fluctuations. In order to isolate the influence of disturbances originating in the incoming shear layer, experiments were conducted in which artificial disturbances were introduced into the flow through air injection in the vicinity of separation. The effect on the reattachment shock system was dramatic: the intensity of the pressure fluctuations and shock motion increased substantially and power spectra of the pressure fluctuations showed a distinct shift to lower frequency. The spectra collapsed onto a common curve in nondimensional coordinates based on a length scale derived from two-point cross-correlations of the flow visualization data and a convection velocity derived from cross-correlations of the pressure measurements. This curve showed fairly good agreement with a theory developed by Plotkin (AIAA J., Vol. 13, No. 8, 1975, pp. 1036-1040), which is based on perturbation of a shock by random fluctuations in the incoming turbulent flow. These results indicate that, unlike separated compression ramp flows where shock motion is associated primarily with relatively low-frequency expansion and contraction of the separation bubble, the shock motion in the reattaching shear layer is primarily caused by organized structures in the incoming turbulent flow.

Original languageEnglish (US)
StatePublished - Dec 1 2000
Event38th Aerospace Sciences Meeting and Exhibit 2000 - Reno, NV, United States
Duration: Jan 10 2000Jan 13 2000


Other38th Aerospace Sciences Meeting and Exhibit 2000
Country/TerritoryUnited States
CityReno, NV

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Aerospace Engineering


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