Oscillatory excitation of unsteady compressible flows over airfoils at flight reynolds numbers

Avraham Seifert, La Tunia G. Packt

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


An experimental investigation, aimed at delaying flow separation due to the occurrence of a shock-wave-boundary-layer interaction, is reported. The experiment was performed using a NACA 0012 airfoil and a NACA 0015 airfoil at high Reynolds number incompressible and compressible flow conditions. The effects of Mach and Reynolds numbers were identified, using the capabilities of the cryogenic-pressurized facility to maintain one parameter fixed and change the other. Significant Reynolds number effects were identified in the baseline compressible flow conditions even at Reynolds number of 10 and 20 million. The main objectives of the experiment were to study the effects of periodic excitation on airfoil drag-divergence and to alleviate the severe unsteadiness associated with shock-induced separation (known as "buffeting"). Zero-mass-flux oscillatory blowing was introduced through a downstream directed slot located at 10% chord on the upper surface of the NACA 0015 airfoil. The effective frequencies generated 2-4 vortices over the separated region, regardless of the Mach number. Even though the excitation was introduced upstream of the shock-wave, due to experimental limitations, it had pronounced effects downstream of it. Wake deficit (associated with drag) and unsteadiness (associated with buffeting) were significantly reduced. The spectral content of the wake pressure fluctuations indicates of steadier flow throughout the frequency range when excitation was applied. This is especially important at low frequencies which are more likely to interact with the airframe.

Original languageEnglish
Title of host publication37th Aerospace Sciences Meeting and Exhibit
PublisherAmerican Institute of Aeronautics and Astronautics Inc. (AIAA)
StatePublished - 1999
Externally publishedYes
Event37th Aerospace Sciences Meeting and Exhibit, 1999 - Reno, United States
Duration: 11 Jan 199914 Jan 1999


Conference37th Aerospace Sciences Meeting and Exhibit, 1999
Country/TerritoryUnited States


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