AIAA Paper 94-1804, 12th Applied Aerodynamics Conference, June 1994


Spectral Measurements in Vortex Flow over Swept-winged

Configurations at High Angle  of Attack

M. A. Klein, J. P. Hubner and N. M. Komerath
School of Aerospace Engineering
Georgia Institute of Technology
Atlanta, GA  30332-0150


 At moderate angles of attack, the vortex flow over swept-wing aircraft develops quasi-periodic velocity fluctuations in the vicinity of the vertical tails.  This paper presents hot-film measurements of velocity spectra in front of the vertical tail tip chord of a 1/32-scale YF-22 and F-117 model and over corresponding flat plate delta wings with sweep angles of 47.7° and 67.0°, respectively.  Spectral results for all four configurations exhibited narrow-band, sharp peaks, whose frequency scaled linearly with freestream velocity at a constant angle of attack.  The variation of the Strouhal number based on mean aerodynamic chord is presented for a range of angles of attack and compared with previous data on other swept-winged configurations.  While the narrow-band spectral phenomenon exists on all configurations tested, the Strouhal relationships for the isolated wing configurations do not match with full configuration results at all angles of attack.  The presence of the body, inlets, and other geometries affect the development of the fluctuations and the corresponding spectral results.